Towards an Integrated Flood Risk Management in Muang Xay 1 TOWARDS URBAN FLOOD RESILIENCE IN MUANG XAY FLOOD RISK MANAGEMENT AND INVESTMENT PRIORITIES FOR URBAN PLANNING AND DESIGN © December 2017 International Bank for Reconstruction and Development / International Development Association or The World Bank 1818 H Street NW Washington DC 20433 Telephone: 202-473-1000 Internet: www.worldbank.org This work is a product of the staff of The World Bank with external contributions. The findings, interpretations, and conclusions expressed in this work do not necessarily reflect the views of The World Bank, its Board of Executive Directors, or the governments they represent. The World Bank does not guarantee the accuracy of the data included in this work. The boundaries, colors, denominations, and other information shown on any map in this work do not imply any judgment on the part of The World Bank concerning the legal status of any territory or the endorsement or acceptance of such boundaries. Nothing herein shall constitute or be considered to be a limitation upon or waiver of the privileges and immunities of The World Bank, all of which are specifically reserved. Project Team Involved stakeholders and Institutions World Bank Ms. Amphone Vongvixay PhD Henrike Brecht Senior Hydraulic Engineer Senior Infrastructure Specialist Mr. Somzay Champathangkham MSc Ministry of Public Works and Transport (MPWT) Dzung Huy Nguyen Senior Flood Risk Modeler/Hydrologist Department of Inland Waterway Transport Senior Disaster Risk Management Specialist Sengthong Vongsakid MSc Public Work and Transport Institute Zuzana Stanton-Geddes Senior Disaster Risk Management Spe- Disaster Risk Management Specialist Department of Housing and Urban Planning cialist Adi Verwey Mr. Bounmy Chayavong MSc Project Officer Senior Flood Risk Management Consultant GIS and Database Specialist Department of Public Works and Transport of Oudomxay Province Ms. Sengkeo Thongvanna Waterway Sector Deltares Project Administrator The Netherlands Road Management Sector Hans Gehrels PhD Australia Housing and Urban Planning Sector Senior Flood Risk Specialist (Team Leader) Mr. John Ward PhD Railway Management Sector Ruben Dahm MSc Economist Planning and Cooperation Sector Senior Flood Risk Modeler/Hydrologist Mr. Nigel Murphy MSc Didrik Meijer MSc Department of Finance (DOF) Social Impact Specialist Senior Flood Risk Modeler/Hydrologist Mr. David Dettrick PhD Department of Public Health (DOH) Govert Verhoeven MSc Reviewer/Senior Flood Risk Modeler/ Department of Education and Sport (DOE) Senior Flood Risk Modeler/Hydrologist Hydrologist Department of Post and Telecommunication (DPT) Ferdinand Diermanse PhD Department of Planning and Investment (DPI) Flood hazard assessment specialist adpc Department of Labour and Social Welfare (DLSW) Laurens Bouwer PhD Thailand Risk management specialist Mr. Anisur Rahman MSc Department of Agriculture and Forestry (DAFO) Dennis Wagenaar MSc Senior Urban Planner (international)w Department of Information, Culture and Tourism (DICT) Damage calculation specialist Mr. Thanongdeth Insixiengmay MSc Lao Water Supply Office, Oudomxay Branch (Nampapa) Elba Stefania Valenzuela Velazquez MSc Senior Disaster Risk Management Spe- Junior researcher/ Graphic Design Urban Development Administration Authority of Xay District (UDAA) cialist Lao Woman’s Union Office of Province (LWU) Singapore Vientiane Geomatic Services Military Headquarter Mr. Marinus Vis MSc Lao PDR Environmental Impact Specialist Mr. Paul Simcock MSc Data acquisition and ground survey Earth Systems specialist Lao PDR Mr. Chris Smithies MSc In-Country Coordinator Executive Summary L ao PDR is regularly impacted by flooding which causes widespread damage to infrastructure and impacts livelihoods. Between 1991 and 2013, on average, 200,000 people per year were affected by floods, which along with droughts pose a serious threat to wellbeing and socio-economic development in the country. Muang Xay, the capital of Oudomxay Province in northern Lao PDR, has been impacted by a number of large flood events, most recently in August 2017, which have caused widespread damage to infrastructure, loss of life and impacted on local livelihoods. Planning for the implementation of infrastructural and non-structural flood control measures is necessary to prevent further loss of life and assets from future flood events in Muang Xay. The population is growing at approximately 3% per annum with high population density in the inner urban areas of the city. Flood zones are yet to be adequately identified and accounted for in urban planning processes and much of the city’s critical infrastructure identified in the study is vulnerable to flooding. Limited enforcement of building and zoning regulations often results in uncontrolled development that may exacerbate future flooding effects. To address these challenges, the World Bank, with support from the Global Facility for Disaster Reduction and Recovery (GFDRR), provided technical assistance to the Government of Lao PDR (GoL) to improve the understanding of the underlying disaster risks and help identify opportunities for investing in integrated urban flood risk management. The findings of this technical assistance support the GoL in preparation and implementation of planned investments in Muang Xay, the capital of Oudomxay Province under the Lao PDR Southeast Asia Disaster Risk Management (SADRM) Project, with financing by the World Bank. This project foresees a combination of proposed structural and non-structural investments for Muang Xay to support integrated flood risk management amounting to ~14 million US$. As part of World Bank’s technical assistance, a A number of infrastructural investments as proposed effect in reducing the flood hazard because maximum study was conducted by Deltares, Earth Systems, by the GoL were assessed in terms of the level of risk river discharges are greatly reduced. When all design Asian Disaster Preparedness Centre and Vientiane reduction that could potentially be achieved, both options, including the reservoirs, are combined into one Geomatic Services, assessing investments proposed individually and combined. The analysis showed that intervention package, the model results show that the by the GoL from different perspectives, including GoL proposed interventions can provide varying levels flood risk for Muang Xay almost completely reduces to disaster risk, benefit-cost analysis (BCA), social and of flood risk reduction with most of the significant zero, with the associated damage (EAD) being reduced environmental impact, and urban planning and design. reductions potentially experienced during floods with with 99%. This includes all return times up to 100 Stakeholder consultations were conducted in the lower return periods (2-,5- and 10- years). Some measures years. It has to be stressed, however, that the current form of several workshops and numerous interviews. were seen as highly effective (river improvements, dikes, conclusions are based on very limited local and open meander shortcut) while others are not so effective (river data. Uncertainty is therefore substantial and should Flood risk assessment parks, flap gates) in reducing flood risk at the spatial scale be reduced before more detailed design is possible. of the river catchment in which Muang Xay is situated. F lood risk was assessed for the city of Muang Xay, The study shows that a significant flood risk reduction Benefit-cost analysis can be achieved with the implementation of the package A and the reduction of flood risk was evaluated for a number of infrastructural design options. of interventions as proposed by the GoL. The results benefit-cost analysis (BCA) was conducted A hydrological and hydraulic simulation model was show that a reduction of expected annual damage and considering combinations of structural and constructed based on the available data of the region. The the number of people that is affected by the flood risk non-structural measures against the Project limited availability of data posed considerable limitations of ~50% when all proposed interventions are combined. budget of approximately US$12.1M. Nine different on the modelling of flood risk. In general, there is a lack investment options were further assessed by multi- of data on hourly rainfall, multiple rainfall stations, As a next step in the analysis, in order to further criteria analysis (MCA) incorporating the BCA stage discharge relations, and specifics on the reservoir reduce flood risk, the design of the most promising rankings with EAD, budget exceedance, alignment with and reservoir operation. River flooding appeared to infrastructural interventions was further optimized. community preferences and environmental and social be the dominant process in the recent flood events. The optimized design show that flood risk can be ratings. Package 8 (reservoirs only) has the highest substantially further reduced in the urban area of composite score largely due to its high BCA and the Flood hazard was modelled and the associated damage Muang Xay. When implementing a combination of river fact that it comes in US$3M under budget. Package was assessed in terms of risk. The expected annual damage improvements, a meander shortcut and dike works, a 6 (Extended river improvement + Park 2 + Nam Kor (EAD) calculated for the current situation without any flood with a return time of 20 years can be prevented in shortcut investment) is the next highest ranked package flood risk management interventions in place amounts the urban area of Muang Xay and the associated damage with Package 9 (all options combined) the lowest ranked to ~11 million US$ per year over the entire area. The (EAD) reduces with ~8.3 M USD per year (~77%). package, mainly due to the extent of budget exceedance. EAD is highest in the western part of Muang Xay near the convolution of the three rivers, with values of over 150,000 Apart from the interventions that were proposed by It is recommended that Package 4 (original GOL proposal USD/year/ha in the area with population densities of the GoL, the potential effect of additional reservoirs + Nam Kor shortcut) is developed within this project over 15,000 people/km2. EAD values for the eastern part or retention areas in the Nam Kor catchment and the potentially resulting in annual EAD reduction of almost of town are generally lower than 100,000 USD/year/ha. Nam Mao catchment has been explored. Simulation 50% compared to the base case. It is further recommended results show that reservoirs potentially have a large that extended river bank protection / river improvement works could be implemented in the medium term and the A key focus of the next phase of the project will be to infrastructure includes recreation grounds, gardens, development of two reservoirs is considered for the longer provide technical assistance to GOL planning bodies parks and green roofs. The implementation of flood term. Initial modeling indicates that the combination of in order to integrate disaster risk management (DRM) hazard mapping exercises, as well as, the implementation the above measures could provide up to 98.7% annual and environmental management aspects into current of programs within communities and schools will reduction in EAD for a 1 in 100-year flood event. urban planning processes. Significant opportunities help in the promotion of flood hazard awareness. are also present for the introduction of low cost, Social and environment impact locally appropriate flood mitigation measures to In conclusion T complement the proposed structural investments such T he proposed investments were subjected to a as retrofitting flood mitigation equipment to existing he results of this study show that flood risk in site based environmental and social screening in-stream infrastructure. During consultations, villagers Muang Xay can almost completely be reduced exercise and an environmental risk assessment. expressed the desire to become more resilient through to zero. These findings, however, are based Key potential environmental and social impacts implementation of community based DRM, flood data on very limited local and open data. We therefore from development of infrastructural flood mitigation collection and early warning systems. Villagers also recommend to further elaborate and detail the design measures include localised dust, noise and sedimentation requested participation in the design, construction options that were considered in the present study. during the construction phase, conversion of non- and maintenance of flood mitigation infrastructure critical riparian habitats, downstream impacts due to including community led blue-green measures. It is believed that the implementation of the above changed flow regimes and the potential requirement for recommendations will improve planning and some resettlement. Although a number of World Bank Urban planning coordination for urban planning and disaster risk management, increased flood resilience among local I Safeguards may be potentially triggered by the project, it is expected that environmental and social impacts from n order to support the development of a Strategic communities, a reduction in the threats posed by flood the proposed investments can be managed and mitigated Integrated Urban Design and Flood Risk Management events for existing and planned infrastructure and positive to an acceptable level by application of environmental Plan for Muang Xay City, a set of guidelines was outcomes for environmental and social management. and social safeguards during the detailed design and developed. Regarding Institutional strengthening the construction phases of the project. There is currently implementation of a three-step planning framework for a lack of flood mitigation infrastructure in place within future urban development is vital. This framework should Muang Xay. DRM laws and planning processes are include a structured plan, urban area plan and detailed/ being institutionalised at the national level but are yet action area plan, at the same time it needs to be flexible to be implemented locally. Current risk management and allow for periodic review, classified land use zoning practices are largely reactive and limited resources options and risk-sensitive land use planning options. to respond to flood events often leaves local citizens Institutions such as PTRI and DHUP should be trained exposed while hampering socio-economic development. on resilient infrastructure design and construction. Experience from past projects shows that complementing Actions to support flood resilience include the adoption structural investments with the implementation of of blue-green measures. Blue infrastructure refers to non-structural measures is critical to project success. wetlands, ponds and wet detention basins; whereas green Content List of Acronyms 01 Introduction 02 Muang Xay Profile 03 Methodology 04 Understanding Flood Risk Management 05 Evaluating Non-Structural Measures 06 Evaluating Infrastructural Design Options 07 Potential Flood Mitigation Investments 08 Conclusions and Recommendations 09 Guidelines for an integrated Urban Disaster Risk Plan References List of Acronyms ADB Financed Urban Infrastructure PTI Public Works and Transport Institute asl Above Sea Level r Discount Rate BCA Benefit Cost Analysis SADRM Lao PDR Southeast Assia Disaster Risk Management BCR Benefit Cost Ratio SIUDFRM Integrated Urban Design and Flood Risk Management CCA Climate Change Adaptation SUDS Sustainable Drainage Systems Desinventar UN’s Disaster Information Management System UDAAS Urban Development Administration Authorities DHUP Department of Housing and Urban Planning VDPCC’S Village Level Disaster Committees DICT Department of Information Culture and Tourism DOW Department of Waterways EAD Expected Annual Damage ESMF Environmental and Social Management Framework GoL Government of Lao PDR GFDRR Global Facility for Disaster Reduction and Recovery HOT Humanitarian Open Street Map Team IDCRM United Nations Integrated Disaster and Climate Risk Management Project in Lao Pdr IFM Integrated Flood Management IFRM Integrated Flood Risk Management LaoDI Lao PDR Disaster Information Database MCA Multi-Criteria Analysis MLSW Ministry of Labor and Social Welfare MONRE Ministry Of Natural Resources and Environment MPI Ministry of Planning and Investment MPWT Ministry Of Public Works And Transport NDRMP National Disaster Risk Management Plan NPV Net Present Value NSEDP National Social Economic Development Plan NSPDM National Strategic Plan on Disaster Management OB Optimism Bias PDPCC Provincial Disaster Prevention and Control Committee PONRE Resource and Environment Office Towards Urban Flood Resilience in Muang Xay Towards Urban Flood Resilience in Muang Xay 01 INTRODUCTION M uang Xay, capital of Oudomxay Province in understanding of the underlying disaster risks and northern Lao PDR, is regularly impacted help identify opportunities for investing in integrated by large flood events, causing widespread urban flood risk management. This was done by damage to infrastructure and impacting livelihoods. It assessing the proposed investment from a technical, is estimated that between 1991 and 2013, on average, social, environmental and economic perspective. The 200,000 people per year were affected by floods, which findings of this technical assistance will support the along with droughts poses a serious threat to well- GoL in preparation and implementation of planned being and socio-economic development in the country. investments in Muang Xay, the capital of Oudomxay Likewise, the frequency and severity of disasters have Province, under the Lao PDR Southeast Asia Disaster increased over the years, and most models predict Risk Management Project, financed by the World Bank. further intensification in the future. This underlines the need to improve disaster risk management (DRM) As part of World Bank’s ‘Lao PDR Southeast Asia and climate change adaptation (CCA) in Muang Xay. Disaster Risk Management Project’ an assessment of structural and non-structural interventions was Despite recent progress in national level disaster planning conducted in collaboration with Deltares, Earth and policy development, key challenges regarding Systems, Asian Disaster Preparedness Centre and integrated flood risk management remain, including Vientiane Geomatic Services. The present publication (i) weak institutions and regulatory frameworks; (ii) draws on a series of technical reports that were written limited meteorological and hydrological forecasting recently in the framework of the World Bank project. capacity; (iii) insufficient financing for resilient sectoral investments; and (iv) low financial resilience to both LAO PDR SOUTHEAST ASIA DISASTER recurrent and extreme disasters due to the lack of MANAGEMENT PROJECT sustainable and cost-effective financial protection W policies and mechanisms. Flood response remains ad- ith the aim to reduce the impact of floods hoc, with limited long-term preparatory action, and in Oudomxay, improve early warning DRM in the country awaits comprehensive development. systems in a number of provinces, and improve financial protection of the country, the GoL To cope with these threats, the World Bank, with is currently implementing the ‘Lao PDR Southeast support from the Global Facility for Disaster Reduction Asia Disaster Risk Management Project’, supported and Recovery (GFDRR) provided technical assistance by financing and technical assistance from the World to the Government of Lao PDR (GoL) to improve the Bank. The project covers two important components: 1 Towards Urban Flood Resilience in Muang Xay Component 1: Integrated Urban Flood Risk In addition, the report provides guidance for developing Chapter 4 provides a description of the Management, to strengthen flood resilience in a strategic integrated urban design and flood risk mechanism of flooding in Muang Xay, as well Oudomxay Province. Structural investments will include management plan for Muang Xay. The development as the relevance of urban planning within the flood protection infrastructure in Muang Xay, including of this strategy is an important step towards the use context of integrated flood risk management. investments in riverbank protection and embankments, of water and floods as a design parameter for spatial floodgates, weirs, river-side parks, and drainage canals. planning, to increase flood risk awareness and to Chapter 5 summarizes the review of priority Infrastructure investments will be complemented with develop practical strategies to cope with flood risk. investments and non-structural measures including non-structural measures, including strengthening The preparation of the strategic plan for Muang urban planning and zoning. It details selected locally land-zoning, institutional capacity-building on Xay City takes the following elements into account: appropriate examples of flood risk management integrated flood disaster risk management, etc. and community resilience measures that may be • Reduction of the adverse impact of applicable in Muang Xay and other parts of the country. Component 2: Hydromet Modernization and Disaster floods and the likelihood of floods; Risk Management Systems, intended to improve • Promotion of sustainable flood risk management; Chapter 6 evaluates the reduction of flood risk the delivery of weather, climate and hydrological • Consideration of opportunities to work with as a result of infrastructural interventions. A services and end-to-end early warning systems in Lao natural processes and where possible, design number of investment options are considered: PDR with physical investments in Oudomxay and dual-purpose facilities delivering multiple river bank protection, dyke construction, river bed Luangprabang provinces, including capacity building. benefits from flood risk management; improvements, construction of flapgates and riverside • Communication, awareness raising and emergency parks. In addition, an environmental and social response assessment of each of the investments is provided. ABOUT THIS REPORT T he present report provides technical support Chapter 2 includes a biophysical and socio- Chapter 7 summarizes an economic assessment of to the city of Muang Xay in the assessment of economic profile of the Muang Xay project area, and priority investments and non-structural measures. The future investments (both infrastructural and provides an assessment of the current situation and economic model quantifies the costs and benefits of non-structural) in urban flood risk management. The arrangements for flood risk management and urban different combinations of structural and non-structural ultimate goal of flood risk reduction is the mitigation planning in Muang Xay City and Oudomxay Province. investments and considers the economic and social of risks of damage to people, built infrastructure, consequences of each option, in order to identify the agricultural lands, or any other urban or rural assets Chapter 3 describes the methodology of flood best possible combinations of no-regret investments that directly or indirectly contribute to the economy and risk assessment for the city of Muang Xay and the for the city within the current project budget. livelihoods of people in Muang Xay. Flood risk reduction surrounding areas, including flood modelling, strategies presented in this report comprise a well- flood hazard and risk mapping with specification of The report ends with conclusions and recommendations balanced mix of both infrastructural and non-structural modelling tools and rainfall-runoff modelling concepts. in Chapter 8 for a Strategic Integrated Urban Design measures, on both short and long-term timescales. and Flood Risk Management Plan for Muang Xay. 2 Towards Urban Flood Resilience in Muang Xay 02 MUANG XAY PROFILE A biophysical and socio-environmental review of 2014 shows that rainfall in Muang Xay has experienced a Muang Xay was conducted. Information was modest decrease . However, rainfall is projected to increase obtained using a combination of desktop research, modestly by 2050 and many climate indicators predict that consultation and data collection with key stakeholders. rainfall will occur in shorter and more intense periods. BIOPHYSICAL CONTEXT Hydrology O udomxay Province is located in the northwest of Oudomxay province has a wealth of water resources Lao PDR and is bordered by China to the north as in three primary watersheds, with approximately well as by five other Lao provinces. The province 66 small and large rivers. The Nam Ko River and its consists of seven districts and 471 villages and covers an tributaries including the Nam Mao, Nam Hin and area of 15,370km2. Oudomxay Province is characterised Nam Sin pass through Muang Xay. The project area is by mountainous terrain and river valleys with elevations confined between three mountains, the upper Nam Kor ranging from 300m to 1,800m above sea level. river mountain to the north and the upper Nam Hin Approximately sixty rivers flow through the province, river mountain and upper Nam Mao river mountain some of which form tributaries to the Mekong River to the southwest. The elevation of the Nam Kor river which flows through the southern part of the province. bank is approximately 636-640 metres above sea level. The provincial capital, Muang Xay, is situated in the north-western part of the province and covers an official Bioregion around Muang Xay area of 399km2 although the majority of the population lives within an area of 72.5km2. Muang Xay is situated in Oudomxay Province is part of the Northern Indochina the Nam Kor river basin and is surrounded by mountains. Subtropical Moist Forests ecoregion. Approximately 85% of the province consists of upland areas (1,306km2) and Climate 15% of lowland areas (230km2). According to statistics from the District Office of Natural Resources and Oudomxay Province has a tropical monsoon climate. Environment in Muang Xay, forested land accounted for Average annual precipitation (1990-2016) at the Muang over 90% of land use in the province with 19.6km2 utilised Xay Weather Station is 1,833mm. Most of the rainfall for agriculture and 23.9km2 for another land cover. Key (90%) occurs in the wet season months from April to agricultural and forestry commodities produced in the September with the highest peaks in July and August. province include rice, corn, rubber, eucalyptus tree, An analysis of rainfall across Lao PDR between 1995 and forest products. Managed forest areas in the province are 3 Towards Urban Flood Resilience in Muang Xay generally divided into three major categories: conservation forests, production forests, and protection forests. Biodiversity There is a wealth of biodiversity in Oudomxay Province. The provincial forests are reported to support tiger, elephant, deer, muntjak deer, bear, boa, turtle, Amyda catelageane, wild boar and many other animals. Plant diversity is also rich with such varieties as agar wood, Phyllanthus Milabilis, hopea, ironwood (Maidengnam), honey orchid, rattan, Debrenaesia hypoleuca, bamboo, mushroom, herbs and other species. DEMOGRAPHICS I n 2015, the population in Muang Xay Town amounted Fig. 2.1 Map of Muang Xay Town and sur- to 35,289 people, of which 51% are female. According rounding terrain. The map shows the main to statistics from the Lao Population and housing rivers located near Muang Xay city as well as Census 2015, Muang Xay has a predominantly young the flood extent of August 2008. population with 72% of people under the age of 35. (Source: DMH,2017) Population density in Muang Xay is 58 persons / km2 based on a total village land area of 604km2. However, most of the population is concentrated in an area of approximately 75km2 indicating that the true population density in many areas is likely to be closer to 400 persons/km2. Muang Xay has more than 14 different ethnic groups, the largest ethnic group (60% of the population) being the Khamu who are a part of the Lao Theung Fig. 2.2 Age-sex data for Muang Xay ethnic people’s category. The other major ethnic 2015 (Source: PHC 2015). 4 Towards Urban Flood Resilience in Muang Xay groups are the Lao Loum and Hmong (Hmong These ratios are only rough indicators of economic Ban Nalao, Ban Nalae, Ban Bor, Ban Houaykhum, Khao, Hmong Dam and Hmong Lai) which account burden, as not all ‘working-age’ people actually work, Ban Donekeo, Ban thiew and Phu That Stupa/temple. for approximately 25% and 15% of the population. while some ‘dependents’ are actually in the workforce. LEGISLATIVE FRAMEWORK FOR FLOOD RISK Vulnerability to flooding The national average for single female-headed MANAGEMENT AND URBAN PLANNING households in the urban area according to the L Vulnerable categories of the population susceptible Population Housing Census 2015 is 17.8%. All to suffer harm from flooding include: poor, villages consulted in the present study reported ao legislative and planning frameworks are now in disabled, elderly, single female-headed households figures below the national average ranging from 3.4 the process of incorporating DRM principles, but and households with limited land tenure security. % in Ban Houaykhoum to 13.3% in Ban Nawan Noi. this is yet to be institutionalised and implemented In terms of land security, most of the consulted on the ground. Urban planning to date in Muang Xay According to the Lao Expenditure and Consumption villages reported a very high level of residential has not considered DRM and suffers from a lack of Survey of 2013, 30% of the population of land ownership ranging from 95% of households data to support design hazard levels across the city. An Oudomxay is considered as poor. It is reported by in Ban Thin and Ban Nasao with permanent land analysis of the legislative framework has been carried local authorities that Ban Houaykhoum and Ban titles to 100% in Ban Nawan Noi and Ban Pasak. out to understand how Muang Xay has been coping Nawan Noi are the poorest villages of the province. with flooding and how urban planning and development INFRASTRUCTURE could increase or reduce flood risk in the city. O Reports estimate that 0.5% of the population (0.3% of female population) have a disability, which is low compared udomxay is connected to Luang Prabang by Institutional Arragement to the national average of 2.8% for both sexes. Ban National Road 1. The town has an energy Nongmaengda village has the highest number of reported supply of 24 hours per day and 21 villages out The administrative hierarchy for urban areas in Lao disabilities with 0.7%, of which 0.4% are female. No of 22 villages have access to drinking water supply. PDR has five levels, the national capital, secondary information is available about the type or level of disability. The main infrastructure for Muang Xay includes 10 towns (Luang Prabang, Savannakhet, Thakek, Pakse), kindergartens, 20 primary schools, 1 lower secondary provincial capitals, district towns and village units (both Figures from the Population Housing Census 2015, school, 9 upper secondary schools, 4 vocational individual settlements and villages within urban areas). report that 3.8% of the population in the Xay District schools and 3 colleges. Regarding healthcare the were over 65 years old and 6% of the population were main infrastructure of the city is composed of one At the national level, the Ministry of Public Works and over 60. The old-age dependency ratio in the Xay provincial hospital, a military hospital, a private Transport (MPWT) is the key agency in charge of urban District is 6 elderly dependents for every 100 working hospital, 30 clinics and one health service facility. planning. Urban development administration authorities age people. National average reports a dependency of Muang Xay city has 11 temples including the temple (UDAAs) manage and implement the financed urban 7 elderly dependents for every 100 working age people. in Ban Thin, Ban Cheng, Ban Nasao Ban Namee, infrastructure (ADB), whereas the economic planning 5 Towards Urban Flood Resilience in Muang Xay for urban development is the responsibility of The NSPDM outlined goals for 2005, 2010 and 2020. The the Ministry of Planning and Investment (MPI). Draft NDRMP (2016-2020) aims to support resilient development under the 8th National Social Economic At a national level, disaster prevention and control Development Plan (2016-2020; 8th NSEDP). The goals is the responsibility of the Ministry of Labour set to be achieved by 2020 were formulated as follows: and Social Welfare (MLSW). An overview of the current institutional arrangements for disaster risk • To make Lao society safer and minimizing the management in Lao PDR is shown in Figure 2 3. impact of disaster on people’s lifes, national economy, public and private property; Flood risk management • To assist victims of disaster, helping them to mitigate disaster impacts and A National Strategic Plan on Disaster Management quickly recover from disaster shocks; (NSPDM) was first issued by the MLSW in April • To integrate disaster management and 2003 with flood risk reduction as the main prevention into legal and economic frameworks focus. The overall aims of the NSPDM are to: from the village to the national level; and • To mainstream disaster management concepts Fig. 2.3 Overview of the current institutional arrangements for DRM • Safeguard sustainable development and reduce and environmental protection within Lao society. in Lao PDR (Source: Earth Systems 2017) the damage of natural or human-made disasters to community, society and country economy; Communication, early warning and evacuation • Shift strategy from relief and mitigation after disaster impact to community, society and The responsibility for DRM coordination has economy of government organizations to moved from the Ministry of Natural Resources and preparedness before disaster strike emphasizing Environment (MONRE) back to the MLSW at the on flood, drought, landslide and fire parallel with national level but provincial and district level line continuing to mitigate in post-disaster period; agencies in Muang Xay are still awaiting formal • Move from government-centered to community- confirmation of the new arrangements. This delay centered approaches in dealing with disaster by has hampered the effectiveness of coordination building adaptive capacity within communities; and and clear lines of communication for early warning • Promote sustainable management of the and evacuation efforts among GoL agencies. environment and natural resources such as forest, land and water. 6 Towards Urban Flood Resilience in Muang Xay At the start of every wet season, letters are sent to village committees about the need to prepare for flooding. The Resource and Environment Office (PONRE) is responsible for early warning through the Department of Meteorology and they currently broadcast the weather situation through district radio once a week on Tuesdays. Information on upcoming storms that may lead to heavy rain and floods is sent from DMH of MONRE to PONRE in Muang Xay. DONRE then sends notifications to the district and the district sends to the village by fax, phone and official letters. Village committees and schools set up information meetings when river levels rise to initiate flood readiness by safeguarding assets and preparing for evacuation if required. At the beginning of a flood event the Provincial Disaster Prevention and Control Committee (PDPCC) will call villages and relevant GoL Above: Overview of rivers crossing agencies. Village committees will then inform villagers rural areas in Muang Xay. by loudspeaker systems and often a volunteer will walk around to inform households in areas of the village too far away from loudspeakers. The most common form of early warning for citizens in Muang Xay is phone contact Operation and maintenance of existing flood According to MPWT there is currently no existing flood by relatives upstream to inform that a flood is on the way. management infrastructure management infrastructure in Muang Xay. Maintenance of all urban infrastructures is largely reactive due to The Department of Waterways (DOW) is responsible lack of assigned budgets for ongoing maintenance. The military is responsible for evacuation efforts for the operation and maintenance of any infrastructure Accordingly, many public assets are repaired after damage during flood events. They conduct disaster emergency on or in waterways within Muang Xay. The UDAA is or drains cleared after blockages have been identified. response training annually and are able to mobilise responsible for operation and maintenance of urban quickly to high risk areas during floods. In addition drainage while the Provincial Public Works and Transport to assisting the population to move to safe areas, are responsible for major repairs of urban infrastructure. the military also assists with asset protection and clean up and recovery efforts after the event. 7 Towards Urban Flood Resilience in Muang Xay 03 METHODOLOGY T his section summarizes the methodology of The outputs of the workshops listed the expectations flood risk assessment. The flood modelling, and objectives of flood-affected interests. They also flood hazard and risk mapping methodology provided the foundation for further multi-criteria are detailed, including the specification of modelling analysis, relevant scenario analysis, data requirements tools and rainfall-runoff modelling concepts. for World Bank economic analysis and the ranking of integrated structural and non-structural flood WORKSHOPS management proposals. Last but not least, the D workshop outcomes provided critical baseline data ecision-making for flood management in for ongoing monitoring and evaluation of project Muang Xay occurs at multiple levels involving initiatives and a preliminary assessment of vulnerability. villagers, vulnerable groups, communities, local authorities and civic bodies. It also involves STAKEHOLDER CONSULTATIONS governments and decision makers from other sectors responsible for related spatial planning decisions. Stakeholder consultations focused on semi-structured interviews with key government stakeholders, the Lao Aiming to include all the stakeholders in the development Women’s Union and village authorities in two flood- of the SIUDFRM for Muang Xay City, a series of affected villages in Muang Xay. Consultations included: structured workshops were carried out in collaboration with the GoL and Muang Xay flood management agencies. • Semi-structured interviews with NGO’s The focus of these workshops was to (i) elicit historical and development organisations and flood exposure, consequences (incl. vulnerability), flood-affected villages in Muang Xay; adaptations and management responses; (ii) scope out • Male and female focus groups with 10 flood affected prevailing flood pressures, proposed structural and non- villages; structural interventions and governance mechanisms; • Multi-stakeholder focus groups with (iii) prioritise stakeholder initiatives and investments government, mass organisations and NGO’s; and that account for levels of impact and uncertainty; (iv) • Participatory workshops. arrange for ongoing participatory processes to report the evaluation of cross-sectoral, structural and non- structural priority actions nominated by participants. 8 Towards Urban Flood Resilience in Muang Xay DATA COLLECTION T he main focus on data collection was existing data from government and stakeholders. Field investigations were focused on site assessments for the proposed investments and further mapping of critical infrastructure. The following data was collected for the development of flood maps: • Location of the main rivers, • Location and characteristics of the bridges, • Information about the weir upstream of Nam Mao bridge, • Cross-sections of ~100 locations (ground survey), • Transects of flood plains at 5 locations (ground survey), • Water levels from two newly installed level stations from July 22 2017 onwards, • Water levels at the Nam Kor bridge 2 of the period 2005-2015, • Water level measurements at the Nam Mao bridge of the period 2010 and 2016, • SRTM elevation data, and • Over 52.000 point height measurements (ground survey). The Department of PWT Oudomxay took members of the project team to inspect an area of the drainage system that has been planned to be converted into a 4 or 5 cell lagoon treatment system. As well, the project team inspected the identified critical infrastructure of Muang Xay city to determine flood risk susceptibility and the potential for flood impacts on operations during flooding periods. Above: Workshop activities and field investigations carried out in Muag Xay city 9 Towards Urban Flood Resilience in Muang Xay HYDROLOGICAL AND HYDRAULIC MODELLING I n the area of Muang Xay, two types of flood mechanisms are considered, pluvial flooding and river flooding. Pluvial flooding occurs when high-intensity local storm events lead to local (urban) flooding due to insufficient drainage capacity or bottlenecks in the urban drainage system. River flooding is caused by heavy rainfall in the upstream catchment, leading to high river discharges and overtopping of rivers. Hydrological and hydraulic models were developed to calculate the flood hazard imposed upon Muang Xay by the Nam Mao, Nam Hin and Nam Kor rivers. The models consider not only the city itself but the entire river catchment area, as river flooding is the dominant flood mechanism in Muang Xay. Hydrological model A hydrological model was constructed to calculate the forcing input for the hydrodynamic modelling. The hydrological model contains data and information on rainfall and evaporation, catchment delineation, land use and soil characteristics to determine the response of the catchment to selected rainfall events. The Deltares WFlow distributed (grid) rainfall-runoff model was used to simulate the rainfall-runoff processes at the catchment scale. This distributed model was run using available global datasets updated with local information. In this study, the SBM conceptual model embedded in WFlow was used. The catchment was also modelled with the HBV model of Killingtveit and Fig. 3.1 Overview of Hydrological model. Muang Xay Rivers Sælthun [1995]. By applying two hydrological models, the uncertainties in the and streams as applied in WFLOW. The grey dots represent hydrological modelling and their impacts on computed flood risks were assessed. the lateral connections. (Source: Deltares, 2017) 10 Towards Urban Flood Resilience in Muang Xay Hydraulic model The Deltares SOBEK modelling suite is used for the hydraulic modelling of the area . A 1D-2D hydraulic model of the river and the area adjacent to the river was developed in order to calculate river flooding. The 1D model includes the cross sections of the river and all existing infrastructure, such as bridges and weirs. The 2D model includes a detailed representation of ground elevation to get a realistic estimation of the flooded area and the water depths in the city. The 1D and 2D models were combined into a 1D-2D model of the city that includes the principal drainage and a detailed elevation model of the urban areas most vulnerable to flooding. The models were calibrated using Fig. 3.2 Overview of 1D2D hydraulic model built in SOBEK. available data of historic flood events and by carrying (Source: Deltares, 2017) out a sensitivity analysis. Flooding was simulated for return periods of 2, 5, 10, 25, 50 and 100 years. can be determined by using an appropriate probabilistic Derivation of river flow statistics computation technique. These steps were followed for each FLOOD HAZARD ASSESSMENT scenario of infrastructural design options. The following The hydraulic model of the Nam Kor catchment has T procedure was carried out to compute the overall flood risk: several (17) inflows, three of which are the most relevant he main purpose of hazard assessment is to derive as they are the upstream boundary flows of the Nam Hin, inundation depths for relevant potential flood 1. Derive upstream boundary flow conditions for Nam Mao and Nam Kor rivers. For the risk assessment, events for the entire project area. The principal the Nam Hin, Nam Mao and Nam Kor for a range it was necessary to derive river flows with return periods approach is to define the range of potential (synthetic) of return periods (2, 5, 10, 20, 50 and 100 years); of 2, 5, 10, 20, 50 and 100 years. These values were events that may cause floods and then to subsequently 2. Simulate the flows with the hydraulic model to based on statistics of peak flows and flow durations. [a] simulate these events with the hydrologic/hydraulic derive flood maps for the same set of return periods model to obtain the inundation depths in the project 3. Compute the total damage for each return period The challenge was the fact that these statistics area and [b] derive the probability of occurrence of each 4. Combine the results of the different return needed to be derived from a limited data set. To event. Based on the combined information of [a] and periods to quantify the overall flood risk derive flow statistics from rainfall data using a [b], the probabilities of inundation depths in the area hydrological model, the following approach was used: 11 Towards Urban Flood Resilience in Muang Xay 1. Simulate the entire period for which rainfall data is available with the hydrological model, resulting in a discharge time series of equal length. 2. Derive discharge statistics from the derived discharge time series. 3. Determine the T-year river flows from the discharge statistics (Time=2, 5, 10, 20, 50, 100 years). Sensitivity analysis of hazard maps Hydrological model simulations were carried out with two different models: HBV and WFLOW. The average annual discharge values appeared to be very similar. Due to the limited availability of data to validate the hydrological and hydrodynamic models, several combinations were tested to provide some insight into the impact of model choice. The inflows for 6 return periods derived from both hydrological models (WFLOW and HBV) and both roughness values (n=0.030 s/m1/3 and n=0.045 s/m1/3) of the cross sections in the SOBEK 1D2D flood model were combined. The model tests for September 2008 and August 2013 events were compared and taken into account for a sensitivity analysis. The results of the WFLOW hydrological model with a roughness value of n=0.045 s/m1/3 showed more accurate results. For this reason, the flood risk assessment and impact Figure 3.3 Flood extent for the reference case, analysis of future interventions continued with the WFLOW hydrological model. flood event of August 2008. (WFLOW; Manning’s coefficient, n = 0.045 s/m1/3) (Source: Deltares 2017) Resulting hazard maps Figure 3.3 shows the combined flood map for the Muang Xay area for the so-called reference case (WFLOW; Manning’s coefficient, n = 0.045 s/m1/3). The more frequent flood events like return periods of 2 years and 5 years are in darker blue and less frequent flood events e.g. return periods of 50 years and 100 years are in light blue. The maps for the various return periods will be used as input for the damage model. The damage model then computes damages for a range of return periods. The resulting damages will subsequently be translated to meaningful risk indicators like the expected annual damage (EAD). 12 Towards Urban Flood Resilience in Muang Xay 3.1 Damage categories and potential damage Damage category Potential damage (USD/person) Residential - Structure 2,717 Residential - Content 906 Non-residential (incl. cars) 1,812 EVALUATION OF FLOOD RISK the global data set population in such a way that construction experts and locals who have experienced F the total population in the map within the village floods. The damage function for the non-residential or purposes of the present report, risk is defined as the corresponds to the known village population. category is a combination of the damage functions combination of hazard, exposure and vulnerability. for building structure, building content and cars. The hazard component is the combination of The construction cost of a house in the area has been probability and magnitude of natural hazards. Exposure estimated by a local contractor to be 48,000 USD for It is questionable to what extent these damage functions is a measure of the assets and population at risk. an average house. Based on experiences with more made for Sri Lanka are applicable to Muang Xay. Vulnerability is a measure of potential exposure losses detailed damage models in many other countries (e.g. Sri Several studies have shown that damage calculations (damages and fatalities) if a hazardous event occurs. Lanka, Afghanistan, USA, the Netherlands, Germany, are relatively sensitive to the damage functions applied UK and Bangladesh) the value of the building content and that transfer of damage functions from one Exposure data was estimated to be 1/3 of the building structure. Also area to another can result in significant inaccuracies based on experiences in other more detailed studies, (e.g. Jongman et al., 2012; Wagenaar et al., 2014). Very little exposure data is available for the Muang Xay the non-residential damage (offices, stores, schools, It is therefore recommended to construct local area. The damage model is therefore based on population hospitals, cars, roads, etc.) was estimated to be 1/2 of the damage functions for future more detailed studies. data and data about important objects such as schools and residential damage. In this way also the non-residential temples. Population per village in the Muang Xay area is damage was included based on the relationship Damage and loss known. Secondly, a high (12m) resolution global dataset is between building information and population data. The available indicating which areas contain buildings (Global resulting damage categories and their corresponding Conceptually it is important to note the difference between Urban Footprint). Thirdly, a countrywide population potential damage per person are shown in Table 3.1. flood damage and flood loss. The term “flood damage” is map is available from WorldPop (100m resolution). related to the physical damage of public and private assets These three sources of data have been combined to make Vulnerability such as infrastructure, houses, contents, agricultural a population map as input for the damage calculation. losses and vehicles due to contact with flood waters. The Vulnerability functions express a relationship between term “flood loss” has a much broader meaning and refers The Global Urban Footprint map was used to filter the water depth and the damage. For this study, these to secondary or tertiary losses, as well as intangible losses out places that are empty and ensure that only areas relationships have been based on similar curve functions such as losses to human life and ecological systems. are included in the model with buildings. The local as created for Sri Lanka (Dias et al., 2017). The damage data with village population was then used to scale functions for Sri Lanka are based on expert meetings with 13 Towards Urban Flood Resilience in Muang Xay Risk calculation Damage calculations were carried out for flood maps at different return periods (2, 5, 10, 20, 50, 100 years). These calculations can be used for the calculation of the expected annual damage (EAD), also known as flood risk. The flood risk is expressed in USD per year and can be shown in the form of a map for a specific situation (e.g. USD/y for each cell of the current situation) or as a total figure for a specific situation (e.g. USD/y for the whole area in the current situation). The advantage of risk maps or risk figures is that the entire flood assessment can be captured in one map or one figure. This makes it easy to compare the current situation with Figure 3.4 Overview of the damage calculation Flooding is most relevant when it leads to damage. Therefore, (Source: Deltares 2017) the situation after future interventions. A second advantage flood maps need to be translated into damage maps. In a of applying risk maps is that it expresses all flood risk in damage map, data about exposed objects is combined with one monetary value that with some further economic a flood map and the vulnerability of these exposed objects calculations can be compared to the cost of interventions. (damage functions). The exposed objects are separated into It is, therefore, an essential input for cost-benefit analyses. a number of different categories of objects (e.g. residential Flood risk is calculated based on the following formula: and non-residential) for which damage functions have been created and for which exposure data has been collected. An overview of the damage calculation is shown in Figure 3.4. The damage calculations were carried out with Delft- FIAT (Flood Impact Assessment Tool). Delft-FIAT is Where: a set of Python scripts that can be applied to set up a Risk = flood risk [USD/y] damage calculation anywhere. It carries out the damage p = The flood exceedance probability [1/y] calculation as shown in figure 5.1 and is completely Damage (p) = The flood damage at different flood probabilities generic. It makes an overlay between user-specified [USD] exposure (objects), flood maps and the vulnerability pmax = The highest probability for which damages are to be ex- to flooding (damage functions) of the specific objects. pected [1/y] 14 Towards Urban Flood Resilience in Muang Xay The flood risk was calculated using inundation maps, land use, vulnerability curves and values at risk (economic exposure) as input. Inundation maps are available from the flood modelling. Land use, vulnerability curves and maximum damages are available from the assessment of exposure and vulnerability. Risk assessment for the reference case Figure 3.5 presents the expected annual damage (EAD) in USD/year/hectare for the reference case (WFLOW; Manning’s coefficient, n = 0.045 s/m1/3). The map shows that damage is higher in the western part of the town. The EAD value for the eastern part of the town is generally lower than 100,000 USD/year/ha. The highest damage is noticed in the area with population densities of >15,000 people/km2   Figure 3.5 Expected annual damage (USD/ year/ ha) for the reference case, flood event of August 2008 (Source: Deltares 2017) 15 Towards Urban Flood Resilience in Muang Xay 04 UNDERSTANDING FLOOD RISK MANAGEMENT INTRODUCTION TO INTEGRATED FLOOD RISK Integrated flood risk management will include MANAGEMENT the implementation of different types of measures I depending on the type of flood. These measures are ntegrated flood risk management (IFRM) is defined generally arranged in a cascade which ensures that as the development of strategies towards a culture all the potential types of measures are consciously of preventions through management of flood evaluated. As illustrated in Figure 4.1 the cascade risk and living with floods. Aiming at maximizing elaborates a number of guiding principles for categories benefits from the use of floodplains while at the same of measures. Additionally, per every type of measure, time minimizing losses and damages, the IFRM there is often a corresponding policy and management integrates land and water resources development. field. It should be noticed that IFRM makes linkages and agreements between measures and policy development. Integrated flood risk management includes five key components: The development of a well-balanced strategy for integrated flood risk management should include a • Adopting an adequate combination of proper understanding of the system, not only examining measures, both structural and non-structural characteristics of past flood events but also looking which have to address long-short events; into future scenarios. This chapter will further describe • Holistic management of the water cycle considering flooding in Muang Xay and the flood hazard that the all types of possible floods (i.e, pluvial, river flooding); development of future infrastructure may pose to the city. • Integration of land and water management; • Adoption of integrated hazard management approaches; • Ensuring a participatory approach aiming to reduce vulnerability. Fig. 4.1 Cascade with Integrated Flood Risk Management measures and corresponding policy and management field. (Source: WMO, 2007) 16 Towards Urban Flood Resilience in Muang Xay UNDERSTANDING THE MECHANISM OF FLOODING IN MUANG XAY T wo types of flooding have been considered for the area of Muang Xay: pluvial flooding and river flooding. Pluvial flooding occurs due to insufficient local drainage capacity or bottlenecks in the urban drainage system, whereas river flooding occurs as a result of high river discharges and overtopping of river banks. A) High river discharge upstream B) Initial flooding near the confluence Figure 4.2 schematically demonstrates how flooding takes place in Muang Xay. Simultaneous high flow discharges of the three rivers (Nam Kor, Nam Hin and Nam Mao) come together just upstream of the Muang Xay city centre (Figure 4.2 A). After the confluence, the narrow river profile causes a reduction in the discharge river capacity, increases of water levels and backwater effects (Figure 4.2 B). Prolonged high river discharges subsequently cause flooding alongside the upstream river banks (Figure 4.2 C). In even more extreme flood events river levels upstream of the city centre may rise to such heights that the flooding bypasses the main river parallel to the airport in the direction of the meander downstream of the Nam Kor River (Figure 4.2 D). Information on past flood events in Muang Xay and Xay District was collected during semi-structured interviews with relevant GoL stakeholders and follow-up data collection with key line C) Flooding along the riverbanks D) Extrem flooding bypassing the river agencies. Further information was collected at the village level. A summary of the collected information is summarised below, key lessons show the main cause of flooding is the result Fig. 4.2 Sequence of flooding events of over-flow of the river banks due to sustained rainfall over schematically depicted for the Muang a preceding period followed by a significant rainfall event. Xay area. (Source: Deltares, 2007) 17 Towards Urban Flood Resilience in Muang Xay 1985: The 1985 flood was a flash flood event that occurred after a week of heavy rain, which caused the Nam Kor and Nam Mao Rivers to overflow. The flood event hit Ban Lak 11 at about 3 am on 25th August before reaching Muang Xay at about 5 am. The 1985 flood event is remembered by local residents and GoL officials as the worst flood event in Muang Xay. 1992: The flash flood event in 1992 occurred due to a landslide. Muang Xay Town was not significantly affected but there was significant damage to the Tad Lak 11 waterfall, a prominent tourism site in Xay District. The flash flood changed the landscape around the waterfall and huts, a shop and a restaurant surrounding the waterfall were destroyed by landslide. 2008: In August 2008, heavy rain caused the Nam Kor River to flood in Muang Xay at about 3 am in the morning. The water levels in Muang Xay increased slowly during the Fig. 4.3 Overlay of the simulated flood map of the September 2008 event on the surveyed flood extent (green flood event which lasted about 6 hours. Many upstream area). The overlay of this simulated flood extent and the survey show a good fit in some parts of the Muang Xay area. However, and as expected in some areas (e.g. near the future river park) there is only a limited fit. Given villages also contacted downstream villages to warn them the available data, the simulation results are considered as acceptable. of the coming flood and this allowed many communities to respond and move assets to areas safely above the flood peak. The extent of the September 2008 flood event has been mapped in a post-disaster study. The map was created by the Infrastructure Development Institute in 2009. This event was used to validate the results simulated with the hydraulic model. 18 Towards Urban Flood Resilience in Muang Xay 2013: The 2013 flash flood, occurred as a result of torrential rains on August 20-21 with maximum daily rainfall of 93.6 mm. Seven districts suffered damage to infrastructure, loss of life (17 persons), and loss of agricultural production up to a value of 1,233 million kips (150,000 USD). Flood damage in the provincial capital of Muang Xay was largely caused by inundation from the Nam Kor River. 2016: According to the provincial flood damage report, twenty- three villages were affected by the flood event between 12th and 15th August 2016. The estimated damage cost for the Nam Mao Pump House was 70,227,850 kip. 2017: According to the provincial report, rainfall recorded during the 4th and 5th August 2017 measured 132.22 mm. On 5th August, the flood event in Muang Xay lasted between 7 am and 6 pm. Letters were sent out to villages warning of the likelihood of flooding at the start of the wet season but there was no formal warning just prior to the event despite heavy rainfall for the 3 preceding days. Once the flood had started, village loudspeakers urged villagers to move their families and key assets to safety in flood-affected villages. Urban infrastructure, utilities, houses, shops and markets nearby both the Nam Kor and Nam Mao rivers were Above: Overview of flood damages in affected. Xay district had eight affected villages of which Muang Xay (Source: Deltares, 2007) five villages were in Muang Xay. 19 Towards Urban Flood Resilience in Muang Xay URBAN PLANNING IN MUANG XAY AND ITS or informal development. In spontaneous housing ROLE IN FLOOD MANAGEMENT areas, houses are developed on an incremental basis by S individual initiatives. One of the major characteristic patial development has rapidly taken place features of urban residential land use growth is that over the last 10 years across the city, especially it follows mainly the access routes and areas of higher along the main roads and rivers (Nam Mao elevation, which have comparatively better service and Nam Kor). The construction of new roads, facilities. However, due to the presence of largely hotels and other infrastructure for hosting the Lao vacant land within the built-up area, there is still plenty National Games and the upcoming Lao-China railway of scope for infilling within the existing urban area. in the southwestern part of the city have greatly influenced the development of the city. However, some The Master Plan has not identified any flood zones developments are not in line with the city master plan. to be brought under development control for flood hazard mitigation and the current planning The master plan has delineated generalized land-use for guidelines for the city do not indicate plinth level the control of urban development. Land use has been standards in different city areas based on past sub-divided into 7 classes: urban area, areas surrounding flood inundation in 1985, 1992, 2008 and 2017. the urban centre, suburb-area, urban expansion area, transport area, agricultural area and forest and nature area. The most recent flood event in August 2017 raised a Agriculture and forest use accounts for approximately number of issues regarding flood risk management and 66% of the surface (4839 ha). The urban centre and inner urban planning in Muang Xay. A number of unapproved urban area account for only 6% of the total area of the developments on the waterways may have exacerbated city, although urban areas are expected to increase by flood damage and flood extent during this event. The up to 29% by the end of the planning year 2021. Rapid case of the Chinese bridge located in Ban Nasao is a clear urban development without appropriate controls will example of how urban development plays a fundamental lead to mixed land use (i.e. residential, commercial, role in flood events. The bridge was constructed civic, and industrial development in the same areas). The without consideration of food risk and dwellings were railway line through the south-western part of the city constructed in high-risk flood areas along the Nam Mao is also expected to influence mixed spatial development. River. Additionally, the bridge was constructed without proper approval from the UDAA, and it did not follow Except for a handful of planned residential areas, almost any standard. During the flood event of August 2017 Above: Buildings affected by flood events in Muang all housing in the city is characterised by spontaneous the natural flow of the water was interrupted through Xay city (Source: Deltares, 2017) 20 Towards Urban Flood Resilience in Muang Xay the congestion of debris, a situation that contributes to the extent of inundation in the surrounding areas. During preparation of the current master plan of Muang Xay, flood hazard information in relation to the city was not available and flood hazards were therefore not considered. As a result, it is not mandatory to consider historical flood heights or levels. Moreover, the master plan does not indicate flood-prone or flood risk areas to guide development. This has resulted in many developments in the city within flood-prone areas. The Oudomxay Provincial Hospital was constructed in the year 2005. The flood height of the area where the hospital is located was inundated up to 1.1 meters in depth during 1985 flood . However, the current plinth level of the hospital is 0.5 meter, which is below the height of the flood level in the area within the last 30 years. Moreover, the 20 years return period flood Fig. 4.4 Flood Extent Map of Different Return Period. Red Circle Area indicates the location of the Oudomxay inundation maps (developed under the project) indicate Provincial Hospital Prone to 20 years return period flood (Source: Deltares 2017) that the hospital location is at high risk (Figure 4.4). • Promotion of sustainable flood risk management Critical infrastructure measures, addressing all phases of the flood risk Developing a strategic integrated urban design and Critical infrastructure prone to damage from flooding management cycle, focusing particularly on flood risk management plan for the city of Muang in Muang Xay includes schools, temples, bridges, damage prevention by avoiding construction of Xay is an important step towards the use of water and hospitals, markets, a power substation, roads and residential, commercial and industrial infrastructure flood management as a design parameter for spatial drainage infrastructure. Analysis of the calculated flood in present and future flood-prone areas or by planning, to increase flood risk awareness and to risk maps shows that much of the infrastructure is located adapting future developments to the risk of flooding; develop practical strategies to cope with flood risk. outside of the inundation areas for events with return • Consideration of opportunities to work with The preparation of a strategic plan for Muang Xay times of 2 years and 5 years, but most infrastructure is natural processes and where possible, design will need to take the following elements into account: at risk for events with return times of T = 20, 50 and 100 dual-purpose facilities delivering multiple benefits from flood risk management; years. Schools are most vulnerable to flooding under • Reduction of the adverse impact of the 1 in 20 year scenario while the provincial hospital • Communication, awareness raising and emergency floods and the likelihood of floods; is under threat from a 1 in 50 or a 1 in 100 year event. response. 21 Towards Urban Flood Resilience in Muang Xay Fig. 4.5 Critical infrastructure and expected flood prone area for a 1 in 2-year flood event (Source: Earth Systems, 2017) 22 Towards Urban Flood Resilience in Muang Xay Fig. 4.6 Critical infrastructure and expected flood prone area for a 1 in 5-year flood event (Source: Earth Systems, 2017) 23 Towards Urban Flood Resilience in Muang Xay Fig. 4.8 Critical infrastructure and expected flood prone area for a 1 in 20-year flood event (Source: Earth Systems, 2017) 24 Towards Urban Flood Resilience in Muang Xay Fig. 4.9 Critical infrastructure and expected flood prone area for a 1 in 50-year flood event (Source: Earth Systems, 2017) 25 Towards Urban Flood Resilience in Muang Xay Fig. 4.10 Critical infrastructure and expected flood prone area for a 1 in 100-year flood event (Source: Earth Systems, 2017) 26 Towards Urban Flood Resilience in Muang Xay 05 EVALUATING NON-STRUCTURAL MEASURES T he development of a well-balanced strategy In holistic planning, flood resilience measures for IFRM consider different types of measures should be designed within the context of the broader depending on the flood type. The adoption of an ecosystem, considering the spatial planning and adequate combination of structural and non-structural architectural style of the area to be implemented. measures helps communities to reduce the negative Aiming to improve flood resilience in Muang Xay, impacts of flooding and to adjust to flood hazards. this section will further explore non-structural issues such as data collection, communication This section focuses on non-structural measures. Flood channels, community resilience, and community forecasting and early warning are effective measures to organization for flood mitigation and adaptation. minimize the negative impacts of flooding. However, there are factors that influence the effectiveness of such Community resilience in flood-prone areas systems, i.e. data sources, communication, decision support, dissemination or notification, coordination, Community resilience to disasters is seen as a key and responses or actions. Hydro-meteorological data component of disaster risk management. Strengthening (notably rainfall and evaporation) are essential to flood community resilience can complement structural forecasting and early warning systems. Key observations measures for flood protection and in some cases on river discharge and river water levels are therefore be even more effective than engineering solutions. vital for the effectiveness of non-structural measures. Community resilience can be measured as the extent to which communities can respond to, and recover In addition to the well-known infrastructural measures, from, shocks or stresses such as flood events (Figure Sustainable Urban Drainage Systems (SUDs) have 5.1 a). Resilient communities are able to function and proved efficient in the reduction of flood damage and sustain critical systems under stress; adapt to changes flood extent. SUDS are adaptive or resilient measures in the physical, social or economic environment; be that usually aim to ‘absorb, delay, store and drain’ water self-reliant if external resources are limited or cut to help reduce peak run-off. This is specifically relevant off, and learn from experience to improve over time. for climate change induced higher rainfall intensities. Typical SuDS measures are infiltration trenches, Disaster resilience has four components: community permeable pavement, detention basins, retention connectedness; risk and vulnerability; planning and basins, bio-swales, green roofs, rainwater butts, and procedures; and available resources (Figure 5.1 b). storage tanks. Applicability of several of these measures depends largely on the local topography, geology, Information relating to the resilience of communities socio-economic development and climate conditions. in Muang Xay was collected during consultations including semi-structured interviews with GoL and mass organisations, interviews with village authorities and 27 Towards Urban Flood Resilience in Muang Xay focus group discussions with villagers in five flood-prone infrastructure damaged in flood events; villages of Muang Xay and organisational focus groups with • Lack of affordable and viable flood insurance options; professional organisations involved in flood management. • Loss of incomes during and after flood events; and • Lack of knowledge about building flood resilient a) The above-mentioned consultations identified infrastructure. both strengths and challenges in terms of community resilience to flood events in Muang Xay. SELECTED BEST PRACTICES EXAMPLES TO INFORM FUTURE URBAN PLANNING AND Strengths in the community included: FLOOD RISK MANAGEMENT A • High levels of literacy and participation in education; • Good access to health services; number of best practice examples of flood risk • Awareness of support options during flood events; management non-structural measures have • Younger members of the community are skilled been selected for their potential to be adopted in the use of smartphone technology; and in Muang Xay. Examples include locally appropriate • Many people in flood-prone areas have built processes and design measures to improve existing two-storey houses so that they can move people infrastructure, adoption of blue-green measures in urban and assets above the water level if required. planning, options to enhance data collection and analysis b) and communications during flood events. Potential Challenges for community resilience include: measures for strengthening community organisation and • Some key village infrastructure is resilience in relation to flood events are also included. currently located in flood-prone areas; Fig. 5.1 Community resilience models • A lack of knowledge and resources for It is recommended that key urban drainage be subject a): Measuring community resilience (Source: Torrens flood protection of homes and other assets; to ongoing maintenance and debris removal. Debris and Resilience Institute 2015) • Lack of training and community planning related to trash racks (such as drainage grates - many already exist) b): Model for community resilience (Source: Torrens flood risk management; should be installed in localised flooding areas to prevent Resilience Institute 2015) • Lack of dedicated village level disaster management damage to infrastructure. If required, urban drainage committees; should be retrofitted for capacity to 1:5 to 1:10 ARI storms to • Many older community members including many assist with lowering damage from pluvial flooding events. village authorities cannot use smartphones and other IT; All bridges and instream structures should be assessed • Lack of funds to repair public and private for debris flow damage potential using appropriate 28 Towards Urban Flood Resilience in Muang Xay guidelines such as US DoT and if necessary debris design solutions for flood mitigation in urban areas flow trash racks and post and rail racks should be (Figure 5 3). During consultations in the present installed at major culverts and bridges if required. study, stakeholders in Muang Xay expressed a Bridge piers should be protected by debris sweepers desire for beautiful green urban spaces. Future if part of the main highway network or are key urban planning and detailed design of the proposed critical infrastructure roads. investments for Muang Xay should therefore incorporate holistic planning principles such Considering the ‘absorb, delay, store and drain’ as those adopted in Dordrecht where possible. approach, blue-green measures in urban systems aim to recreate a naturally oriented water cycle Data collection and analysis while contributing to the amenity of the city by bringing water management and green Information technology has allowed for the infrastructure together. Blue-green measures can development of powerful tools to support data be an effective tool for flood mitigation in growing collection and analysis in a range of applications. urban areas like Muang Xay. Selected examples of tools and their applications that could be used in Muang Xay in either the Blue infrastructure includes ponds, flowing short or medium term are provided below. waterways, wet detention basins and wetlands that exist within the drainage network. Green Humanitarian Open Street Map and UN-ASIGN infrastructure refers to natural land and plant- Above: Thematic approach of blue-green measures for based ecological treatment systems and processes, The Humanitarian Open Street Map Team (HOT) flood mitigation in urban areas in the city of Dordrecht. such as open space, parks, recreation grounds, manage information collected for a range of potential (Source: ADPC 2017) woodlands, gardens, green corridors, vegetated applications including disaster management. ephemeral waterways and planted drainage assets Information can be collected by virtually anyone with that undergo a wet/dry cycle due to runoff. a smartphone or tablet using open source software and potential applications for disaster management There are many examples of blue-green measures include community disaster preparedness mapping implemented for flood risk management and city and mapping to support humanitarian aid efforts. development along riparian areas. The city of HOT implements projects across the world to meet Dordrecht in the Netherlands is a good example identified needs in partnership with governments and of a thematic approach of blue-green ecosystem development partners (including the World Bank). 29 Towards Urban Flood Resilience in Muang Xay UN-ASIGN is a free application to support emergency local and community level authorities in Muang Xay and their situation or to try to find missing family and friends. response and disaster risk reduction. The application MONRE who is responsible for managing the database. allows individuals to collect and disseminate crowd- sourced photos and reports about the situation in a Flood data apps One disadvantage of over-reliance on mobile technology given area during a natural disaster or humanitarian is that it may alienate those members of the community crisis. Information is time stamped and geo-tagged There are a number of smartphone applications that are technology illiterate or do not own smartphones and uploaded to a central UN server which allows for recently developed for data collection and flood and this bears consideration when designing locally comparison of disaster extent in a given area over time. preparation. Examples include FloodMap and the appropriate communications protocols for DRM. Another The application has successfully been used in Haiti, Red Cross Flood app. The FloodMap app is currently is that it relies on operational networks and services may be Pakistan, Nigeria, Nepal and for flooding in Thailand. only applicable to the US but already has contributed cut for short or even extended periods during flood events. to flood risk information sharing and benefited, Lao Di / MM system for recovery and reconstruction homebuyer’s, property developers and insurance Community Organisation professionals to identify flood risks in different areas. Several disaster information systems have been developed Strong community organisation is vital to resilient for application in Lao PDR. LaoDi has been developed Communication Channels communities that are able to respond to the risks that in partnership with MONRE under the United Nations disasters present to livelihoods, the local economy, Integrated Disaster and Climate Risk Management Project Traditional information channels during disaster events infrastructure and the environment. There are in Lao PDR (IDCRM) and is designed as a repository for in Muang Xay include television, radio, telephone, village currently no village level disaster prevention and disaster information. LaoDI is based on the UN’s Disaster meetings and village loudspeakers. Telecommunications control committees in the villages consulted in Muang Information Management System (Desinventar) and is a company Unitel also has an emergency hotline that can Xay despite them all being in flood-prone areas. tool that helps to analyse disaster trends and their impacts be used in a disaster event but is currently not equipped to in a systematic manner to facilitate improved planning handle large volumes of calls and it works independently for prevention, mitigation and preparedness measures in from GoL. Lao PDR currently ranks seventh in Southeast order to reduce the impact of disasters on communities. Asia for internet use with over 1.5 million internet users and had more than 55 mobile cellular subscriptions for LaoDI is still in the early stages of development and its every 100 people in 2016. The deadly Nepal earthquake effectiveness is currently limited because of the lack of in 2015 is an example of what is possible when leveraging data available in the database. In the short term, the LaoDI available technology during and after a crisis. While voice system could be best utilised best to support decision services were overwhelmed, the internet was still up and making in Muang Xay. This would require better systematic running. Both Facebook and Google enabled services communication and information exchange between allowed citizens and travellers to post information about 30 Towards Urban Flood Resilience in Muang Xay 06 EVALUATING STRUCTURAL MEASURES T his chapter summarizes the effects of the Dikes or river levee banks implementation of infrastructural measures on flood risk mitigation. The priority investments Dikes or river levee banks are earthen flood options considered in this analysis include river bank protection embankments, and are proposed for protection, dike construction, river bed improvements, various locations across Muang Xay spanning a construction of flap gates, river side parks, and reservoirs total distance of approximately 8km. The banks upstream of the city. In addition, this chapter provides an environmental and social assessment of each of the GoL of the river sections are to be raised to withstand proposed investments as well as other potential structural higher flood levels. Future dike levels should be at solutions identified in the flood risk assessment. least 1m above highest current embankment level. The GoL proposed investments were treated to an Flap gates initial site environmental and social screening exercise during the study. Results of the screening exercise The schematized urban drainage network is considered to are presented in this chapter along with an initial be extended with flap gates. This allows only one-directional assessment of the other above mentioned potential flow from the drain towards the river. If the water level in structural solutions. The ISO31000 Risk Management the river is above the bed level of the drainage network, and Assessment framework approach was adopted to develop an environmental and social risk assessment this flap gate blocks any inflow into the drainage system. for flood-prone villages in Muang Xay region. Up to 26 flap gates have been proposed by DOW at strategic PRIORITY INVESTMENTS PROPOSED BY GOL locations along the waterways in Muang Xay. According R to the DOW, the flap gates are designed to improve and iver flooding is seen as the main cause of regulate drainage mainly in small tributaries to the Nam flooding in Muang Xay. Interventions to reduce Kor River. There is no current final design for the flap river peak levels are therefore important. gates but they are expected to span between 4m to 6m. The proposed interventions focus on increasing the discharge capacity of the river in combination with River improvement bank protection. As defined by the GoL The structural solutions for Muang Xay proposed by the GoL include river bank protection, urban discharge systems with The intervention of river improvement as proposed by enhanced infiltration, dike construction, riverbed the Government focuses on increasing the discharge improvements, -flapgates and riverside parks (Figure 6.1). capacity of the river in combination with bank protection. Details on the local context of the river 31 Towards Urban Flood Resilience in Muang Xay a) b) c) Above a): Artist impresion of Park 1 Above b): Schematic of the master plan Park 2 Fig. 6.1 Location map showing proposed investments Left c): Concept of typical cross section of riverside improvements (Source: Earth Systems, 2017) (Source: Deltares, 2017) 32 Towards Urban Flood Resilience in Muang Xay improvement are unavailable yet. Hence, for the river improvement measure, the present study initially assumed a trapezium profile (1:1.5), a lower roughness value of n= 0.030 s/m1/3 (i.e. a smoother bed and wall surface), and a dike level of 1m above the highest embankment. For the bank protection measure we also assumed a trapezium profile (1:1.5) and a lower roughness value but no dike level. River parks The proposed river parks could contribute to the beautification of Muang Xay city. It is assumed that these parks will enlarge the storage of the floodplain at a level of 1m below the nearest bank heights. The river park along the Nam Mao River is assumed to become 3 ha in size, while the river park along the Nam Kor River is assumed to become 14 ha. Shortcut of the river meander in the Nam Kor The meander downstream of the Nam Kor GS extends the river with 2.5km while a shortcut, would be approximately 0.3km in length. Such a shortcut would decrease the backwater effect of the meander on the water level by reducing the flow path. We assumed a design cross-section and bed level based on the cross sections that were surveyed upstream and downstream of the shortcut. Fig. 6.2 Simulated flood extent map after the implementation of all measures (flood event August Initial results 2008) (Source: Deltares, 2017) The impact of these interventions has been assessed by comparing the flood extent and the expected annual damage (EAD) after implementing each intervention with the reference (no interventions) flood situation. The flood extent and the expected annual damage of each intervention were assessed for return periods of 2, 5, 10, 25, 50 and 100 years. For each of the interventions maps of flood extent, EAD and reduction in EAD (compared to the reference case) were constructed, as well as a Fig. 6.3 Expected reduction of chart expressing the reduction of the flood extent, a table showing the reduction flooded area after implementation of in damage, affected population, and the number of affected schools and temples. all measures (Source: Deltares, 2017) 33 Towards Urban Flood Resilience in Muang Xay Fig. 6.4 Expected Annual Damage after implementation Fig. 6.5 Reduction in EAD after implementation of all measures. (Source: Deltares, 2017) of all measures combined . (Source: Deltares, 2017) This information is presented in detail in Report 2 of The expected annual damage for all interventions population affected is reduced by 41% and 43% this study. The present section summarizes the detailed combined is shown in Figure 6.4 and the associated respectively. Schools are extremely vulnerable to analysis by showing the impacts on river flooding reduction in EAD compared to the flooding of flooding, but by implementing a combination of for the combination of all structural interventions. 2008 is given in Figure 6.4. It is estimated that the all the structural interventions, the risk of flooding combination of all interventions reduces the EAD decreases considerably. In general, flood reduction The combination of measures provides a significant considerably. In a large part of the area, the EAD has may decrease up to 50% if all the structural reduction in all areas of the flood extent (Figure 6.2). reduced by at least 13,000 USD/year/ha (green colour interventions proposed by the GoL are implemented. Figure 6.3 displays the reduction in flooded area in km2, in Figure 6.5). Results shows that the decrease in ranging from a maximum reduction of 55% for a return damage and population is up to ~75% for the lower period of 2 years to 6% for a return period of 50 years. return periods. Also, yearly expected damages and 34 Towards Urban Flood Resilience in Muang Xay OPTIMIZATION OF STRUCTURAL INTERVENTIONS T he initial results of the implementation of the interventions proposed by the GoL were discussed with stakeholders, the World Bank and GoL during a workshop held in September 2017. In addition, a series of dedicated field visits in September provided further detailed information on certain system characteristics. An important conclusion was that some measures are very effective (river improvements, dikes, shortcut) while others are not so effective (parks, flap gates) in reducing flood risk at the spatial scale of the river catchment in which Muang Xay is situated. This section describes the next step to further optimize the most promising design options in a package of infrastructural interventions to maximally reduce flood risk. The premise is that river flooding is the dominant cause of flooding in Muang Xay. The priority in the approach is therefore to mitigate the problem of river flooding. River flooding takes place at the scale of the river valley floor, surrounded by the higher grounds. Interventions should therefore also be focused on solving the problems at that same scale level. Rather than only assessing the impact of certain measures on all return times, the interventions are optimized for a 20-year return time. A 20-year return time approximately coincides with a discharge that can be maximally accommodated through the urban river profile without radically widening the riverbed into the urban fabric, i.e., without considerably removing housing and infrastructure. River basin approach Starting from a river basin perspective, the rivers of Muang Xay were subdivided into three sections: upstream of the city, downstream of the city, and in the city centre (‘midstream’). The infrastructural measures were therefore Figure 6.6 Hypothetical catchment locations of potential new reservoirs in the Nam Kor re-designed and added to the intervention package in a stepwise approach: and Nam Mao catchments. The reservoir in the Nam Hin catchment is an existing reservoir. (Source: Deltares, 2017) 35 Towards Urban Flood Resilience in Muang Xay Upstream Upstream of the city, interventions focus on reducing the discharge arriving at the city centre. In the Netherlands and in a number of other countries, a well-known water management principle is to ‘retain, store, use, reuse, and only discharge when necessary’. Interventions should, therefore, be focused on water retention, water storage and peak shaving. In addition to the interventions already proposed earlier, the upstream analysis also includes the assessment of two additional reservoirs for retention and storage. Figure 6.6 shows a map with the hypothetical reservoirs that were assumed in the calculations. Downstream Downstream of the city, interventions focus on increasing the discharge leaving the city centre. In other words, river conveyance should be maximally improved. An option that specifically applies to Muang Xay is short-circuiting the impressive river meander in the Nam Kor. The measures considered for this case include river improvements and shortcut (short-circuiting the river meander). Midstream Along the river stretch in the city centre, in between upstream and downstream, Fig. 6.7 Simulated flood extent for the updated there is little room for water, and the focus was on flood protection by creating flood event of August 2008 levee banks or dikes to prevent the water from overtopping the river banks. (Source: Deltares, 2017) Attention was paid to removing obstructions (e.g. bridges) from the river course. Optimized results Based on the field inspections, the hydraulic model was further improved. The dimensions of a number of structures were adjusted and the conveyance integration techniques were applied with more detail to the local side wall resistance at specific sections of the model schematization. 36 Towards Urban Flood Resilience in Muang Xay Fig. 6.8 Expected Annual Damage (USD/year/ha) for the updated Fig. 6.9 Simulated flood extent after implementing all four measures (river improvements, reference case. (Source: Deltares, 2017) schorcut, dikes and reservoirs) compared to the reference case (flood event of August 2008) (Source: Deltares, 2017) These adjustments to the model schematizations resulted subsequently translated to the expected annual damage as case. These results are presented in detail in Report 2 in an updated flood hazard map as presented in Figure an indicator of flood risk. The EAD for Muang Xay after of this study. The present section only summarizes the 6.7. The simulated flood extent for a 20 year return optimization of the hydraulic flood model is 10.9 M USD. detailed analysis by showing the impacts on river flooding period is approximately 9.2 km2. The maps for the for the combination of all structural interventions. various return periods were used as input for the damage As in the previous section, the impact of all interventions model. The damage model then computes damages for has been assessed by comparing the flood extent and EAD a range of return periods. The resulting damages were after implementing each intervention with the reference 37 Towards Urban Flood Resilience in Muang Xay The combined effect of all structural interventions implemented upstream, downstream and midstream of Muang Xay, shows a substantial reduction in flood extent for all return periods. The flood extent for a 2-year return time and for a 5-year return time is completely eliminated. For the 10-year and 20-year return period only a limited flood extent remains. For a 50-year and 100-year event the flood extent is limited to the rural area in the west of the city centre and does not bypass the river anymore Fig. 6.10 Expected reduction of flooded area after implementation (Figure 6.9). Figure 6.10 displays the reduction in the flooded area, ranging from a of all four measures. (Source: Deltares, 2017) maximum of 100% for 2-year return period to 68% for 100-year return period. The combined effect of the set of measures on water levels in a longitudinal profile from Nam Mao Bridge 3 to Nam Kor Bridge 1 shows a considerable reduction in water levels, ranging from 1.5 to 4 m upstream and from 5 to 7 m downstream near the city centre of Muang Xay (Figure 6.11). Results show an enormous decrease in yearly expected damage. Almost 98% of the damage cost can be avoided if all the interventions are implemented. Additionally, a reduction of almost 100% on yearly affected population is achieved. It can be concluded Conclusions The updated designs of the flood mitigating measures and the subsequent updated flood damage and risk assessment show that with a combination of downstream, midstream and upstream measures flood risk can be substantially reduced in the urban area of Muang Xay. The primary solution for reducing the flood risk is increasing the discharge capacity of the Nam Kor river downstream of the confluence of the three rivers. The discharge capacity of the Nam Kor river downstream of the confluence is currently limited as the flow has to squeeze through the narrow river profile at Fig. 6.11 Longitudinal profile showing the decrease in water levels resulting Muang Xay centre. At extreme flow conditions the combined inflow of the Nam from the implementation of all four measures for a 20-year return period. Kor, Nam Hin and Nam Mao rivers exceeds this capacity and hence flooding occurs. (Source: Deltares, 2017) 38 Towards Urban Flood Resilience in Muang Xay The most promising flood mitigation measures from package, the model results show that the flood risk exercise including the DOW, the PONRE, the UDAA, the the set of measures proposed earlier by the GoL were for Muang Xay almost completely reduces to zero. No Department of Housing and Urban Planning (DHUP) re-designed in order to create a 20-year return period flooding is simulated anymore in the urban area for and the Public Works and Transport Institute (PTI). protection level for the city centre of Muang Xay. To return periods up to 100 years and for lower return increase the discharge capacity, river improvements periods (2-years and 5-years) flooding is completely Each of the reference sites was assessed according and the implementation of a meander shortcut were eliminated. The total damage (EAD) is reduced by 99%. to the five types of screening covered in the ESMF re-designed. Additional dike works were re-designed forms: initial screening, project safeguards screening, along certain stretches along the river to protect the It has to be stressed that the current conclusions flood risk management infrastructure, ethnic urban area of Muang Xay. With implementing this set are based on very little local and open data. groups, and land acquisition and resettlement. of measures, flood risk in the urban area of Muang Uncertainty is therefore substantial and should be Xay can be prevented and the total damage reduces reduced before a more detailed design is possible. Park 1 with 77% compared to the reference case without interventions. ENVIRONMENTAL AND SOCIAL ASSESSMENT According to discussions with the World Bank on the OF POTENTIAL INFRASTRUCTURAL FLOOD 2nd October 2017, the current design for Park 1 would In this approach, following the reasoning by the GoL for MITIGATION MEASURES involve a significant conversion of non-critical habitats A one-sided flood protection dike works, the floodplain and would result in a narrowing of the existing Nam of the river valley (west of the city centre) essentially table with environmental and social rating Mao river channel which could potentially exacerbate functions as a water retention area. A more detailed criteria has been created for each of the potential flood problems instead of providing flood mitigation. analysis could perhaps reduce uncontrolled flooding structural solutions. Five environmental and three The World Bank, therefore, consider Park 1 as a here in favour of more controlled water inlet and social criteria were developed based on a literature review Category A project in its current state which makes it storage. of impacts from flood mitigation infrastructure as well as ineligible for funding. It is suggested that alternative consultations in Muang Xay, the environmental and social designs are considered that either mitigate flooding or In addition to these measures, the potential effect screening exercise and the environmental risk assessment. are at the least, flood neutral during this study. of hypothetical upstream reservoirs in the Nam Kor and Nam Mao catchments were explored. Simulation As part of the environmental and social assessment for this Park 2 results show that such reservoirs potentially have a study, a screening exercise was conducted for the proposed large effect in reducing the flood hazard due to the investments using templates developed in the project The land beyond the riparian areas at the Park 2 site is effect of reducing the maximum peak discharges. Environmental and Social Management Framework already heavily developed and consists of a sports stadium (ESMF 2017). The exercise was conducted in September with a ring road. The riparian areas are predominantly When all design options, including the hypothetical 2017 and involved site visits to reference sites for all of the vegetated with grasses, weeds and some larger trees. There reservoirs, are combined into one intervention proposed investments. A number of local and national is also some evidence of annual cropping and perennials government line agencies participated in the screening 39 Towards Urban Flood Resilience in Muang Xay 6.1 Environmental and social rating criteria Environmental criteria Social criteria Flow regime Protection of individual assets Sediment / channel structure Protection of community assets Water quality Protection of community assets such as bananas. The design of the site at Park 2 would Habitat / biodiversity / natural resources involve a significant conversion of non-critical habitats Construction impacts along the Nam Kor River and potentially includes Source: Earth Systems 2017 deepening and widening of the riverbed. The proposed river diversion would help to reduce flooding at the Park 2 site but may also have implications for flooding downstream. In addition, the diversion would effectively for residential or commercial purposes. The screening Environmental assessment of flood risk management cut off approximately 2.5km of existing waterway which category for each of the proposed investments is highly infrastructure would greatly alter the landscape and have a significant dependent on final design but would be a Category B at the impact on existing water resource use in the area. minimum due to the above-mentioned considerations. According to DICT the proposed floodgates are not located in any areas of cultural significance. PONRE The current design including the diversion may make Environmental assessment of flood risk management were unsure if there are any rare or endangered species of the proposed investment a Category A project and infrastructure flora or fauna at proposed flap gates sites (or affected by this requires consideration at the detailed design stage. changed stream flow due to flap gates) and this requires Both the river improvement and river bank protection further investigation. Modelling showed that the flap Environmental assessment works will result in a significant change in local surface gates are unlikely to provide effective flood mitigation. Initial modelling indicates that the current park design water hydrology on the Nam Kor River. The river will provide little flood mitigation. While deepening and improvement works are expected to facilitate rapid Dikes / river levee banks widening of the river and the proposed river diversion removal of excess water from the inner urban area during may reduce localized flooding, it may also increase the heavy rainfall events but the downstream implications According to DOW, there are currently no final designs likelihood of flooding downstream and this requires of the investment require further investigation. for this proposed investment and this limited the close investigation during the detailed design phase. screening activity to largely a hypothetical assessment. Flap gates Depending on the design of the embankments, a number River improvement and riverbank protection of World Bank policies may or may not be triggered. DOW representatives were of the belief that any adverse The river improvement works are likely to significantly impacts from the flap gates would be modest, confined to Environmental assessment of flood risk management alter the surface water hydrology of the waterways small areas, temporary (during high flow events) and easy to infrastructure at the three sites while the river bank protection will control. Under these circumstances, World Bank policies involve removal of a significant amount of vegetation may not be triggered by the proposed investment but Surface water hydrology will be expected to change and potentially, the acquisition of some land within more investigation is required at the detailed design phase. due to increased channel velocities during elevated the river ROW that is currently occupied by villagers flow peaks in areas subject to embankment works and 40 Towards Urban Flood Resilience in Muang Xay a large amount of vegetation will need to be removed US$4.625M. It is likely that the development of the environmental issues for the installation of flood from riparian areas along the 8km of embankments. reservoir would trigger a number of World Bank protection works and measures are described in Table 6.2. The removal of riparian vegetation will impact on policies including OP 4.01 Environmental Assessment macroinvertebrate and possibly fish populations locally. and OP 4.04 Natural Habitats. OP 4.12 Involuntary The ISO31000 Risk Management and Assessment Resettlement and OP 4.10 Indigenous People may framework approach was adopted for the mitigation of Environmental and social screening of other also be triggered depending on siting of the reservoir. the environmental impacts caused by the implementation potential flood mitigation measures of the infrastructural measures. A qualitative risk Environmental assessment of flood risk management assessment approach was adopted based on the risk Nam Kor shortcut infrastructure formula, risk = hazard x exposure. The assessment of key flood protection measures and impacts is undertaken The river diversion (shortcut) has been proposed to Storage of water in reservoirs alters water quality. using a pre and post mitigation framework to highlight remove a flooding bottleneck where the Nam Kor Anaerobic processes often dominate due to lack of oxygen the relative value of management measures to lower River meanders adjacent to the Park 2 site in order to transfer in standing water. Stratification in the reservoir identified environmental threats and hazards. The increase water discharge during flood events. According can create temperature changes within the water body results of the assessment of key risks to environmental to DOW, there are currently no final designs for this and this needs to be considered in the release of water and social aspects are presented in Table 6.3. proposed investment and this limited the screening from the reservoir. The reservoir may impact migratory activity to largely a hypothetical assessment. It is likely fish in the area by changing surface water hydrology and that the development of the shortcut would trigger natural flow regimes. Reservoirs can also interrupt the a number of World Bank policies including OP 4.01 natural flow of sediment and organic material which Environmental Assessment, OP 4.04 Natural Habitats provides vital nutrients for downstream food webs. and OP 4.12 Involuntary Resettlement. OP 4.10 Indigenous People may or may not also be triggered. ENVIRONMENTAL RISK ASSESSMENT ISSUES AND FINDINGS I Upstream reservoirs n this section, only the change in environmental risk Upstream reservoirs have been considered as a measure due to the operation of potential flood mitigation to reduce flooding in Muang Xay during flood events works is assessed. Several environmental issues although design, operation and siting of the potential have been identified as already having effects on the reservoir are conceptual at this stage. Initial modelling is environment of Muang Xay, some of these may be based on the Nam Hin Reservoir which was constructed exacerbated by flood protection works and will require between 2001 and 2009 at a cost of approximately careful management to prevent further issues. Key 41 Towards Urban Flood Resilience in Muang Xay 6.2 Flood protection measures and potential associated environmental issues Flood Protection Measure Environmental Issues River Levee Banks, Dikes Sedimentation and Bank erosion during construction Loss of riverbank amenity Noise and vibration during construction Increased flow velocity and riverbed scouring Instream Dams and Weirs Sedimentation during construction Fish passage and fish migration barriers Sediment deposition Reduction/increases in water temperature Reduced bedload sediment nutrient supply Eutrophication and oxygen sag Debris accumulation Floodgates and Flaps Prevention of fish passage Debris accumulation Localised flash flooding Poor urban drain water quality due to lack of dilution during flood periods Flood parks Sedimentation and Bank erosion during construction Noise and vibration during construction Odours from sediment, mud and debris after flooding Storage of flood water of poor water quality and evapo-concentration of flood water River diversions Sedimentation and Bank erosion during construction Loss of riverbank amenity Noise and vibration during construction Increased flow velocity and riverbed scouring Nam Kor shortcut Noise and vibration during construction Loss of habitats in the river meander Loss of riverbank amenity in the river meander Increased flow velocity and riverbed scouring Upstream reservoirs Sedimentation during construction Fish passage and fish migration barriers Sediment deposition Reduction/increases in water temperature Reduced bedload sediment nutrient supply Eutrophication and oxygen sag Debris accumulation Source: Earth Systems 2017 42 Towards Urban Flood Resilience in Muang Xay 6.3 Flood mitigation work environmental risk assessment Environmental Expected Pre-mitigation Key Management and Mitigation Measures Residual Impacts and Significance Threat Impact Significance Sedimentation MODERATE Construction stormwater controls Reduced impact of habitat loss – LOW Riparian and forest land use controls Stormwater and sewage treatment Sediment design in flood parks Reduced water quality LOW Construction stormwater controls General water quality issues are at low risk of being Riparian and forest land use controls impacted by flood works – LOW Stormwater and sewage treatment Sediment design in flood parks Riverbank erosion HIGH Appropriate geotechnical and flood structural engineering All instream and bank structures subject to flood and collapse Rip rap design and bank armouring design assessment. This should largely prevent Riparian zone management bank collapse – LOW Planning controls to prevent building and non-compliant development on riverbanks Construction stormwater controls Riparian zone loss MODERATE Replacement of riparian vegetation where possible Some riparian zone loss is inevitable but can be Retention of areas of habitat throughout flood work areas minimized, and preserved with planning Use of riparian zones for flood abatement, velocity inhibition – MODERATE Aquatic habitat loss HIGH Replacement of aquatic habitat where possible Aquatic habitat loss can be minimized, and prevent- Retention of natural pool/riffle design throughout flood work areas ed with good engineering design Locally Retention of riparian vegetation – MODERATE, Retention of woody debris in stream substrate Overall – LOW Loss of fish passage MODERATE Replacement of aquatic habitat where possible Fish passage can be maintained with good engi- Retention of natural pool/riffle design throughout flood work areas neering design Engineering design of fish passage structures in high-velocity areas or hydraulic barriers. – LOW Creation of short “swim distances” between preserved habitat areas Loss of river and HIGH Sensitive multipurpose/use river bank and hydraulic design River amenity value loss can be minimized, and riparian amenity Incorporation of flood structures in riverine architecture and community planning prevented with good engineering design Strategic location of flood protection infrastructure – MODERATE Water quality impacts HIGH Design of instream and off stream storages to minimise oxygen and temperature effects Water quality fluctuations can be minimized with of in-stream struc- Mixing zone modelling to ensure water quality is maintained good engineering design and stormwater manage- tures Design of drainage to prevent build-up of sediment or low oxygen water ment Management of construction phase stormwater – MODERATE Sedimentation design in flood parks Dust, Noise and HIGH Construction sites are kept wet for dust suppression After noise and dust controls are enacted during Vibration impacts Hours of operation used to prevent noise problems construction –LOW Construction vehicles and systems selected for noise sensitive areas Traffic management Source: Earth Systems 2017 43 Towards Urban Flood Resilience in Muang Xay 07 POTENTIAL FLOOD MITIGATION INVESTMENTS T he outputs of proposed structural flood mitigation Package 1 (short term / budget constrained): investments and non-structural measures for flood River bank protection / extended river improvement risk management combined with the preferences works only. Community preference - low. expressed by stakeholders during the workshop series provided the basis for the development of a benefit-costs Package 2 (short term / budget constrained): analysis (BCA). Flood risk modelling and the damage The original GOL proposal (River bank protection assessment considered both the original and variations / river improvement works, dikes / levees and of the set of structural measures proposed by the GoL. River park 2). Community preference - medium. Non-structural flood risk management measures include opportunities for urban planning, community managed Package 3 (short term / budget exceeded by US$1M): early warning systems and DRM. The environmental River bank protection / extended river improvement plus and social assessment and stakeholder values identified the Nam Kor shortcut. Community preference - medium. during consultations were also considered in the analysis. Package 4 (short term / budget exceeded by US$1M): The BCA includes an assessment of direct benefits and The original GOL proposal (River bank protection / river losses in relation to the potential investments over a improvement works, dikes / levees and River Park 2) plus return period of 2 years through 100-year return periods. the Nam Kor shortcut. Community preference - high. An optimism bias (OB) of 60% and 30% have been incorporated to account for the uncertainties typically Package 5 (short term / budget exceeded by US$0.8M): associated with projects in early stages of development. River bank protection / extended river improvement Discount rates of 12% and 6% have been applied plus River park 2. community preference - medium. over a 20 year time period. The analysis estimated benefit-cost ratios, net present value and internal Package 6 (medium term / budget exceeded rates of return for nine Investment options classified by US$1.8M): River bank protection / extended as budget constrained and non-budget constrained. river improvement plus River park 2 plus the Nam Kor shortcut. Community preference - high. This section summarizes the BCA and a multi- criteria analysis (MCA) of nine different short, Package 7 (medium term / budget exceeded by medium and long term investment packages that were US$1.8M): River bank protection / extended river developed for the consideration of decision makers. improvement plus dikes / levees plus River park 2 plus The nine investment packages are detailed below: the Nam Kor shortcut. Community preference - high. Package 8: (long term / under budget by US$3M) Reservoirs only. Community preference - medium. 44 Towards Urban Flood Resilience in Muang Xay 7.1 Cost summary of proposed structural and non-structural investments for flood management Investments Unit Length Cost US$ Structural River Bank Protection m 7,834 6,658,900 investments Levees/dikes m 9,279 4,175,550 Based on two reservoirs similar to the Nam Hin Flap gates No 26 208,000 Reservoir, which was constructed at a cost of ~US$4.5M. River Improvement m 2,000 300,000 Package 9: (long term / budget exceeded bu Riverside Park No. 800,000 US$13M) Flood prioritization (T20 damage=0) Non-structural Zoning, planning, building codes 1,000,000 + all options. Community preference – high. investments Project management 1,000,000 BENEFIT-COST ANALYSIS Total cost 14,142,450 T Source: Lao PDR Ministry of Public Works and Transport and Department of Water (2017) he benefit-costs analysis conducted as part of the Oudomxay flood management project addressed the objectives of IFRM: that is to minimize loss of life, livelihoods and assets from flooding while maximizing The relative costs of implementing structural and non- Optimism bias is the tendency for appraisers and decision the net productive benefits derived from floodplains. The structural measures evaluated in Chapter 4 and 5 are makers to be overly optimistic in early assessments of combinations of investment and non-structural initiatives summarized in Table 7 1. These costs are used as a project costs, time scales and benefits in comparison were formulated from modelled flood reduction base for the development of the benefit-cost analysis. to the actual effectiveness of flood reduction and the investments proposed by the Government of Lao PDR associated values. An optimism bias of 60% is typically and community needs and responsibilities derived from The initial damage calculation for Muang Xay estimates used for projects at an early stage of consideration (see a series of facilitated participatory based processes. the number of houses in 6,360 households located for example UK Environmental Agency 2017) . At the in 22 villages within the Muang Xay precincts and more detailed project stage, a figure of 30% is more Muang Xay flood management decisions will be mean household size of Muang Xay of 5.52 members. commonly used. The BCA of flood investment options partially focused on how to allocate the cost of taking The damage calculation for return periods 2, 5, 10, for Muang Xay applies a sensitivity analysis approach by risk placed on society, assigned amongst governments 20, 50 and 100 years used to calculate the EAD of modifying the optimism bias coefficient (ranging from (central, regional and local governments), and affected the flood event in August 2017 are summarized in 30-60%) to estimate potential losses and damages in interests (such as private companies), communities Table 7 2. These values represent the initial set of addition to the direct costs that occur due to flooding. and individuals. The benefit-cost analysis is primarily reference damage costs used for further BCA analysis. aimed at flood managers and decision makers, including The value of the discount rate influences the relative key community groups, involved in formulating flood The cumulative damage reductions for the set of management strategies and policies. The results are costs and benefits related to flood management flood interventions, including the Nam Kor shortcut intended to provide rapid access to information that across return periods were imputed into the first strategies through time. The discount rate compares risk-sharing mechanisms and allocations as iteration of the BCA calculations and detailed in represents the cost to those affected by floods part of the overall Muang Xay flood management strategy. Table 7 3. Note that the estimated reductions exceed (and their expected level of reward) of abstinence the 40% reduction in flood-affected population from present-day consumption, by postponing set out as a primary objective of the project. flood mitigation to some future date. The World 45 Towards Urban Flood Resilience in Muang Xay 7.2 Expected annual damage across six return periods (baseline: flood of August 2008) Return period (y) Damage Population affect- Utilities and services electricity PWT: roads and Agriculture (USD, M)1 ed (no.) supply, education (USD, M) 2 bridges (USD, M) 2 (USD, M) 2 2 5.7 2,200 0.15a 0.75 a 0.40 a 5 15.8 6,300 0.20 a 1.00 a 0.50 a Bank NPV estimates of the proposal were 10 31.2 11,800 0.259 b 1.50 b 0.61b based on a discount rate of 12 percent, as per 20 49.7 13,600 0.28b 2.4b 1.15b World Bank guidance where discount rate is 50 68.6 14,800 0.35 a 4.5 a 3.0 a calculated as twice the national growth rate. 100 79.2 15,200 0.70 a 7.0 a 5.0 a Yearly expected (EAD) 10.9 3,500 0.97 0.43 For comparative purposes, the Muang Xay BCA analysis adopted a conventional approach Source: 1 Task 2 report. 2 Government of Lao PDR (RT10=2013, RT20=2017), a: linear interpolation estimates only; b Govt of Lao PDR of selecting sensitivity bounds that attempt to reflect alternate versions of the discount rate 7.3 Estimated reduction in damage and population ,and schools affected after appropriate to the investment context. A 12% implementation of all proposed structural measures including shortcut (as per World Bank) and 6% discount rate were applied over the 20 year time period. Return period (y) Reduction in Reduction in Pop- Reduction in Damage (%) ulation affected Schools affected (%) (no.) RESULTS T 2 96.2% 95.5% 0 5 90.0% 90.5% 2 he first step in the development of 10 85.8% 89.0% 8 alternative investment packages 20 86.1% 89.0% 18 was the development of four 50 44.8% 19.4% 20 investment scenarios based on the original 100 29.7% 9.0% 21 GoL proposal (refer to Table 7-1) and Yearly expected (EAD) 76.6% 80.3% 2 community preferences identified during Source Report 2 (section 6) consultations and participatory workshops. * Values represent the reduction in damages after implementation of all proposed structural measures including the shortcut of the Nam Kor river. The four investment scenarios are as follows: Lao PDR Scenario 1: estimates the NPV and BCR of flood damage reduction for structural investments only: River bank protection, levee/dike 46 Towards Urban Flood Resilience in Muang Xay 7.4 Summary of investments options r=6% and 12%, OB=30% and 60%   Baseline Lao PDR Lao PDR Lao PDR Lao PDR scenario 1: scenario 2 + scenario 3 + scenario 4 structural zoning and early warning + tourism a planning (a) construction, river improvements and the Riverside park. The zoning and BC metric Discount rate 12%, OP 60% (US$ m) planning was assumed to have zero effect on flood reduction damages. PV damages 122 80.42 73.50 66.59 66.59 Avoided losses 41.69 48.61 55.52 55.52 Lao PDR Scenario 2: estimates the NPV and BCR of the structural investments NPV 22.4 29.3 36.2 38.1 of Scenario 1 plus reductions associated with non-structural investments (that is urban planning, flood zoning and enforcement). Non-structural BC ratio 2.16 2.52 2.88 3.19 investments were assumed to result in a further 10% reduction in flood damage. IRR (NPV =0) 48% 58% 70% 82%   Discount rate 12%, OP 30% (US$ m) Lao PDR Scenario 3: estimates the NPV and BCR of the structural investments PV damages 122 80.42 73.50 66.59 66.59 of Scenario 2. The budget line originally assigned to flap gates was reassigned Avoided losses 41.69 48.61 55.52 55.52 to developing a community based early warning system (focussed on improved NPV 26.0 32.9 39.8 41.5 response times to reduce the costs of damaged good, chattels and contents). BC ratio 2.66 3.10 3.54 3.95 IRR (NPV =0) 82% 120% 148% 168% Lao PDR Scenario 4: estimates the NPV and BCR of the structural investments of Scenario 3 plus the additional tourism and economic benefits   Discount rate 6%, OP 60% (US$ m) derived from the River park. Tourism benefits were entered as negative PV damages 211 153.71 140.47 127.27 127.27 costs and conservatively estimated as an annual return of River park = Avoided losses 56.82 70.06 83.26 83.26 $16,000 (20% return p/a based on WB estimates) + a 2.7 multiplier (indirect NPV 36.2 49.5 62.7 65.0 and induced effects: WTTO 2015); with growth estimated at 5.7% pa. BC ratio 2.76 3.40 4.04 4.56 IRR (NPV =0) 48% 58% 70% 82% The estimates of present value, net present value and benefit-cost ratios at a   Discount rate 6%, OP 30% (US$ m) discount rate of 6% and 12% (r) and optimism bias (OB) of 30% and 60% for the 4 PV damages 211 153.71 140.47 127.27 127.27 scenarios are summarized in Table 7 4. It can be observed that the value of a 60% Avoided losses 56.82 70.06 83.26 83.26 optimism bias increases the estimated cost by US$7.81M. The objective of project NPV 40.1 53.3 66.5 68.6 management then is to minimize the cost inflation imposed to address predicted cost increases and ideally reduce the additional costs to zero. The optimism bias is BC ratio 3.40 4.19 4.98 5.67 generally reduced to 30% when design details have been finalized and fully costed. IRR (NPV =0) 82% 120% 148% 168% Source: Earth Systems 2017 47 Towards Urban Flood Resilience in Muang Xay Return period Damage Damage Damage Damage (y) reduction reduction reduction reduction (with Nam Kor Reservoirs Reservoirs all shortcut) options 2 91.4% 94.6% 97% 100.0% The net present value and BC ratios are positive for all 5 79.7% 86.4% 95% 100.0% the investment scenarios across all discount rate and 10 65.6% 74.4% 91% 100.0% optimism bias options. The accounting for additional tourism benefits (entered as negative costs) assigned 20 56.3% 65.9% 79% 100.0% to the River parks has the highest BC ratio. Internal 50 31.2% 44.5% 53% 96.5% rates of return range from 46%-168% across the 100 19.5% 28.7% 35% 92.9% investment scenarios and sensitivity analyses. ALTERNATIVE FLOOD DEFENCES A revised set of investment options was modelled including extending the river bank improvements and river dredging extension only package meets the budget constraint Including both the Nam Kor shortcut and the River to 12 kms compared to the original 7.83 kms and of US$11.9M. The original Lao PDR Government park increases the investment expenditure by $1.8M the construction of upstream reservoirs. The proposal is associated with an NPV and BC ratio and decreases the NPV to 59.7 and the BC ratio to 3.64. total cost (applying the original per metre rates) of $38.1M and 3.19 respectively. Both options of the extension equals US$12M or the total of assume the non-structural and community The trade-off for the higher NPV and BC ratio of the proposed budget. The NPV and BC ratio was early warning system reduce flood damage the extended river improvement only compared to calculated using damage reduction values for the by 10% each, representing the recommended the original Government proposal is the omission extended river improvements (with and without) combination of budget constrained structural and of the River park in the investment portfolio and the Nam Kor shortcut, the reservoirs only and non-structural flood management interventions. associated tourist and cultural benefits. The cost the full set of flood management investments of the Nam Kor shortcut was estimated at US1.0M as modelled in this study (see Report 2). The NPV and the BC ratio of the extended river compared to the $US0.8M estimate for the River improvement were estimated at US$51.8M and 3.71 park. Substituting the Nam Kor shortcut with At a discount rate of 12%, OB of 60% and assuming by adding the River park and attendant benefits the River park achieves the requirements of the the 10% additional flood damage reduction of the estimated for tourism (increasing investment community but reduces the NPV by US$13.5M planning investment, the NPV and BC ratio for expenditure by US$ 0.8M). Including the Nam Kor and the BC ratio 3.72 or a reduction of 17%. the river extension only package was estimated shortcut (increasing investment expenditure by US$ at US$ 54.6M and 3.72 respectively. The river 1.0M) increases the NPV to 60.6 and the BC ratio to 3.79. A final investment option introduced an upstream 48 Towards Urban Flood Resilience in Muang Xay reservoir option and the full set of investments. MULTI-CRITERIA ANALYSIS PACKAGES the reservoirs only package is associated with the T The option calculates the NPV and BC ratios for highest level of uncertainty, offers minimal short- the combined flood damage reduction of river he nine investment packages were subjected term flood reductions, and potential sites have not extension, dikes, the Nam Kor shortcut, River park to a multi-criteria analysis which included been evaluated. Package 6 (Extended river protection and upstream reservoirs. The option represents a benefit cost (BC) ratio, expected annual / improvement + Park 2 + Nam Kor shortcut) is the flood risk approaching zero for a 20 year return time. damage (EAD) reduction, budget exceedance, next highest ranked package although it exceeds Reservoir costs were estimated at US$9M based on alignment with community preferences, and the current budget by almost US$2M. Package 3 the construction costs of the recently completed environmental and social ratings (Table 7 5). For BC (extended river protection / improvement + Nam Nam Hin dam in Muang Xay. Importantly, the costs ratio and EAD reduction the highest ranking package Kor shortcut), Package 4 (GOL proposal + Nam Kor are approximations only as the final site has not been was given a score of nine and all other packages were shortcut) and Package 5 (extended river protection / determined and the final costs are likely to vary. The given as score out of nine expressed as a percentage improvement + river park) were equally ranked the option represents the ideal flood risk management of the highest score. Budget exceedance was also next highest. Package 9 (all options combined) is option where the budget is not constrained. scored out of nine with the lowest cost package the lowest ranked of the nine investment packages, scoring a nine, highest cost scoring a one and other mainly due to the magnitude of budget exceedance. At a discount rate of 12%, OB of 60% and packages scaled in between. High community assuming the 10% additional flood damage preference (high community amenity and high flood Across all investment combinations, Package 8: reduction of the planning investment, the reduction) scored a value of 9, medium preference Reservoirs only, has the highest composite score NPV and BC ratio of the reservoirs only were scored 6 (either high flood reduction or high and is therefore ranked highest across the five calculated at US$ 63.6 and 3.5 respectively. community amenity) and low community preference dimensions of flood risk reduction, largely due to (low community amenity and low flood reduction) the high BCA and being $3M under budget. Note The reservoirs only option (approximate cost only scored 3. Environmental and social ratings for the the reservoirs only package is associated with of US$9M) is associated with an NPV of US$63.6M respective investment packages were averaged out the highest level of uncertainty, offers minimal and a BC ratio of 3.5. Including the extended river of 8 based on ratings from Report 3 (Chapter 5). short-term flood reductions, and potential sites improvement and dikes / levees (increasing the have not been evaluated. Package 6 (Extended investment expenditure by US$13M) revises the NPV Across all investment combinations, Package 8: river protection / improvement + Park 2 + Nam and BC ratio to US$58.9 and 2.16. The additional Reservoirs only, has the highest composite score Kor shortcut) is the next highest ranked package tourism benefits of the River Park increase costs and is therefore ranked highest across the five although it exceeds the current budget by almost by a further US$0.8M and the NPV and BC ratio dimensions of flood risk reduction, largely due to US$2M. Package 3 (extended river protection / were calculated at US$ 58.3 and 2.14 respectively. the high BCA and being $3M under budget. Note improvement + Nam Kor shortcut), Package 4 49 Towards Urban Flood Resilience in Muang Xay 7.5 Multi-criteria analysis of packages Investment packages BC ratio EAD Budget Community Environmental Total reduction exceedance preference and social* score Package 1 Budget constrained: Extended river 7 (3.72) 6 (61%) 7 3 6 29 protection / improvement only. Community preference - low. Package 2 Budget constrained original GOL proposal. 6 (3.19) 4 (41%) 7 6 5 28 Community preference -medium Package 3 Extended river protection / improvement + 6 (2.99) 6 (69.2%) 6 6 6 30 Nam Kor shortcut. Community preference - medium. Budget exceeded by US$1M Package 4 Original GOL proposal plus Nam Kor 6 (2.99) 4 (48.6%) 6 9 5 30 shortcut. Community preference - high. Budget exceeded by US$1M Package 5 Extended river protection / improvement + 7 (3.71) 6 (61%) 6 6 5 30 River park. Community preference - medium. Budget exceeded by US$0.8M Package 6 Extended river protection / improvement 8 (3.79) 6 (69.2%) 4 9 5 32 + River park + Nam Kor shortcut. Community preference - high. Budget exceeded by US$1.8M Package 7 Extended river protection / improvement 6 (3.15) 7 (76.6%) 2 9 5 29 + dikes + park + Nam Kor shortcut. Community preference - high. Budget exceeded by US$5M Package 8 Reservoirs only. Community preference - 9 (4.53) 7 (79.4%) 9 6 5 36 medium. Environmental impacts unknown. Under budget by approximately US$3M* Package 9 Flood prioritization (T20 damage=0) 4 (2.14) 9 (98.7%) 1 9 5 28 + all options. Community preference – high. Environmental impacts unknown. Budget exceeded by approximately US$13M * Where multiple structural solutions are employed, environmental and social ratings are averaged. ** Based on two reservoirs similar to the Nam Hin Reservoir which was constructed at a cost of ~US$4.5M. 50 Towards Urban Flood Resilience in Muang Xay (GOL proposal + Nam Kor shortcut) and Package ranked equal highest ranking in the multi-criteria estimates, the extended river improvement works 5 (extended river protection / improvement + analysis. Package 4 had the highest community would cost approximately an extra US$4M and river park) were equally ranked the next highest. preference and is therefore the recommended short- in combination with Package 4, could provide Package 9 (all options combined) is the lowest term package although Package 5 is the best short- approximately 76.6% reduction in annual EAD ranked of the nine investment packages, mainly due term investment package based purely on flood compared to the base case (refer to Package 7). to the magnitude of budget exceedance. mitigation potential. Both packages exceed the current budget by approximately US$1M but there Long term recommendation: Development DISCUSION OF SHORT, MEDIUM AND is scope for partial implementation of both packages of flood reduction reservoirs. LONG-TERM PACKAGE RECOMMENDATIONS in order to work within the project budget without A significantly reducing EAD. For example, river bank The viability of additional upstream reservoirs n important aspect of this study has protection works have been costed based on use will be investigated during the detailed design been the need to involve the local of rip rap in riparian areas. Low cost alternatives phase of the project. Initial modelling indicates community in the development of a such as vegetative solutions (i.e. vetiver grass) that the addition of two reservoirs similar in structural investment package that provides could be used as a more attractive and cheaper size to the Nam Hin Reservoir in combination effective flood mitigation as well as aligning with alternative. Also, the length of river improvement with the recommended short and medium-term community aspirations. This needs to be factored / river bank protection works could be shortened investments, could provide up to 98.7% annual into recommendations for short, medium and by prioritising locations to optimise effectiveness reduction in EAD. Based on construction costs for long-term investment options for Muang Xay. of the investment during the detailed design phase. the Nam Hin Reservoir, the cost of two additional Similarly, dike works can be potentially optimised reservoirs would be approximately US$9M. Short term (this project) recommendation: by prioritising embankments in certain areas Package 4 with prioritization of river based on modelling conducted (refer to Report 2). improvement / river bank protection and dike works to work within the project budget. Medium term recommendation: Implementation of extended river improvement works. In terms of the short-term investment packages, Package 3 (extended river protection / improvement If Package 4 (GOL proposal + Nam Kor shortcut) + Nam Kor shortcut), Package 4 (GOL proposal is implemented during this project then a logical + Nam Kor shortcut) and Package 5 (extended medium term solution would be to extend river protection / improvement + river park) were the river improvement works. Based on initial 51 Towards Urban Flood Resilience in Muang Xay 08 CONCLUSIONS AND RECOMMENDATIONS CONCLUSIONS rivers exceed this capacity and hence flooding occurs. F lood risk was assessed for the city of Muang Xay The expected annual damage (EAD) calculated for in Oudomxay Province, Lao PDR. In addition, the current situation without any interventions in the reduction of flood risk was evaluated place (the reference case) amounts to ~11 million for a number of infrastructural design options. USD per year over the enitre area. The EAD is highest in the western part of the town near the convolution Assessing flood risk of the three rivers, with values of over 150,000 USD/ A hydrological and hydraulic simulation model was year/ha in the area with population densities of over constructed based on the available data of the region. 15,000 people/km2. EAD values for the eastern part of The limited availability of data posed considerable town are generally lower than 100,000 USD/year/ha. limitations on the modelling of flood risk. In general, there is a lack of data on hourly rainfall, multiple Impact of interventions proposed by the Government of Lao PDR rainfall stations, stage discharge relations, and specifics on the reservoir and reservoir operation. We analysed the impact of all infrastructural interventions as proposed by the Government of Lao PDR (GoL). River flooding appeared to be the dominant process in the An important conclusion was that some measures are events in 2008, 2013 and 2017. The analysis shows that the very effective (river improvements, dikes, meander primary solution for reducing the flood risk is to increase shortcut) while others are not so effective (river parks, the discharge capacity of the Nam Kor river downstream flap gates) in reducing flood risk at the spatial scale of of the confluence of the three rivers Nam Kor, Nam Hin the river catchment in which Muang Xay is situated. The and Nam Mao. The discharge capacity of the Nam Kor computations show that a significant flood risk reduction river downstream of the confluence is limited as the flow can be achieved with the implementation of the package of has to squeeze through the narrow river profile in Muang interventions as proposed by the GoL. The computations Xay centre. At extreme flow conditions the combined show a reduction of expected annual damage and the inflow of the Nam Kor, Nam Hin and Nam Mao number of people that is affected by the flood risk of 52 Towards Urban Flood Resilience in Muang Xay ~50% when all proposed interventions are combined. of the river valley (west of the city centre) essentially RECOMMENDATIONS functions as a water retention area. More detailed Further optimization of design options Further detailing of design options analysis could perhaps reduce uncontrolled flooding In order to further reduce flood risk, the design of here in favour of more controlled water inlet and storage. In the preparation of the detailed design phase the most promising infrastructural interventions we recommend to further elaborate and detail the was further optimized and flood risk recalculated. In addition to these measures, the potential effect of design options that were considered in the present Instead of assessing the impact of each measure on hypothetical reservoirs in the Nam Kor and Nam Mao study. River improvement, shortcutting of the all return times, the design of the interventions was catchments were explored. Simulation results show that Nam Kor meander and dike works are the logical optimized to create a 20-year return period (T=20) reservoirs potentially have a large effect in reducing the flood first step to prepare for the detailed design phase. protection level for the city centre of Muang Xay. A hazard due to the decrease in maximum peak discharges. T=20 protection level approximately coincides with A first exploration of implementing upstream reservoirs a discharge that can be maximally accommodated When all design options, including the reservoirs, are for water storage in the Nam Kor and Nam Mao rivers through the urban river profile without radically combined into one intervention package, the model results proved to be very promising. Even though the present widening the river bed into the urban fabric, i.e., without show that the flood risk for Muang Xay almost completely analysis was very preliminary, we recommend to considerably removing housing and infrastructure. reduces to zero. No flooding is simulated anymore in the further investigate the feasibility of realizing reservoirs urban area for return periods up to 100 years and for in the preparation of the detailed design phase. The updated designs of the flood mitigating interventions lower return periods (T2 and T5) flooding is completely and the subsequent updated flood damage and risk eliminated. The total damage (EAD) is reduced with 99%. After detailing the priority interventions at the assessment show that flood risk can be substantially catchment scale, we recommend to zoom in on: further reduced in the urban area of Muang Xay. When It has to be stressed, however, that the current implementing a combination of river improvements, a conclusions are based on very limited local and open 1. The city centre, to complement river flood protection meander shortcut and dike works, a T=20 flood in the data. Uncertainty is therefore substantial and should with localized options on flap gates, river parks, urban area of Muang Xay can be prevented and the total be reduced before more detailed design is possible. urban drainage and greening of the river banks. damage (EAD) reduces with ~8.3 M USD (~77%) per year. 2. The rural area west of the city centre, to increase flood In this approach, following the reasoning by the GoL for protection for lower return times in combination with one-sided flood protection dike works, the flood plain controlled retention for higher return times. The single 53 Towards Urban Flood Resilience in Muang Xay sided dike on the east side of the river that protects with building a database record of these data sets that Short, medium and long-term structural investments the city centre could be complemented with a lower will greatly contribute to future hydrological studies. packages dike on the west side to protect the rural area with Future hydraulic modelling rice paddy fields for the lowest return times without It is recommended that Package 4 (GOL proposal + losing the storage capacity for higher return times. The current model set-up can be extended with global Nam Kor shortcut) is developed within this project 3. The interference of the proposed flood intervention rainfall forecast products or regional/local rainfall which could reduce annual EAD by up to 50% based on design with the construction of the future railway forecasts to move towards a flood forecasting system initial modelling (refer to Report 2). River improvement line west of the city. It is thinkable to design the for the Muang Xay area. When the information of the / river bank protection and dike works within the railway in such a way that it may be neutral to urban micro drainage system is made available, this can package will need to be optimised in order to reduce flood risk or even be part of the flood protection be added to the existing flood modelling framework. costs as the package is currently US$1M over budget. design and contribute to reducing the risk. The August 2017 flood event could be used for model validation as soon as more information becomes In the medium term, extended river improvement We recommend to continue the dialogue on flood available, such as (hourly) rainfall data, water levels, works could further reduce annual EAD to protection levels as was done in the workshops of the discharge, flood extent, flood depth, and damage. approximately 75% compared to the base case present study. After having explored all flood protection at an additional cost of approximately US$4M. Damage modelling options, choosing flood protection levels for different zones within and outside the city (i.e. zonation) is The current damage assessment is based on limited Over the longer term, the further addition of two reservoirs a policy decision and essentially a political choice. data and on several assumptions. It is therefore (at a cost of approximately US$9M) could almost recommended to collect more detailed exposure data, eliminate flooding in Muang Xay for a 1 in 100 year event. Data collection and monitoring more detailed damage categories and better estimates We encountered a lack of data on hourly rainfall, of the potential damage. It is also recommended multiple rainfall stations, stage discharge relations, to formulate local vulnerability functions based on and specifics on the reservoir and reservoir empirical data, experience of the local community and/ operation. Although it is realized how difficult, time or observed flood damage. In addition to improving consuming and costly it is to acquire these data, we do the calculation of direct damage it is recommended recommend to install monitoring programs to start to identify and assess indirect damage as well. 54 Towards Urban Flood Resilience in Muang Xay 09 GUIDELINES FOR AN INTEGRATED URBAN DISASTER RISK PLAN T he implementation of structural and non- public participation into the planning process to structural measures in Muang Xay is ensure that planning reflects public expectations necessary to prevent further losses of life and planning solutions account for local needs; and assets in the city. Therefore, a set of guidelines • Development of a specific sub-plan for protection of were developed to assist with the development of critical infrastructure in flood-prone areas of the city; an integrated urban disaster risk plan for the city: • Development of a detailed urban risk assessment guideline; and REGULATORY STRENGTHENING • Development of new zoning areas to support the integrity of the plan including survey Strong support for government urban planning and delineation of riparian buffer areas and DRM agencies is critical to the success of plan and enforcement of no development zones development. Strategies for regulatory strengthening within the project include but are not limited to: CAPACITY BUILDING • Development of urban design standards to support Planning institutions including PTRI and DHUP implementation of the Urban Planning and DRR have identified the need for capacity building in Manual; several areas to support plan development and project • Integrate DRM and environmental protection into land implementation. Training activities will also be relevant use regulations, building codes and housing standards; to other GoL authorities, particularly from the designated • Employment of a three-step planning package in implementing agencies. Proposed activities include: future urban plan development (structure plan, urban area plan and detailed / action area plan). • Conduct of GIS training to support urban The package needs to be flexible and allow for planning incorporating elements such as periodic review, classified land use zoning options risk assessment and database management; and risk-sensitive land use planning options. The • Training on resilient infrastructure design and package also needs to integrate mechanisms for construction; and 55 Towards Urban Flood Resilience in Muang Xay • Development of tailored general training Promoting community resilience in Muang Xay Other recommendations for the next phase of the packages to support plan development and project project implementation. Modules could include • Establishment of village level disaster Leveraging partnerships: flood modelling, water sensitive urban design, committees (VDPCC’s) across Muang Xay • Identify and pursue partnerships to leverage urban drainage design and maintenance, gender prioritising villages most prone to flooding; development in key areas (ie. Plan International - mainstreaming, and resettlement action planning. • Implement a community level feedback mechanism gender issues, WFP - establishment of village disaster for the project through the VDPCC’s. Once prevention and control committees, flood hazard ACTIONS TO SUPPORT FLOOD RESILIENCE IN established, VDPCC’s have a mandate through to mapping, ADB – planned drainage project); and MUANG XAY the national level and this should help to ensure • Engage telecommunications companies and the effectiveness of the feedback mechanism; and relevant GOL departments about supporting Actions to support flood resilience identified in the • Conduct detailed flood hazard mapping specialised services during disaster events. project included the adoption of blue-green measures exercises in flood-prone areas of the city. In the and activities to promote community resilience. absence of detailed flood risk data for Muang Environmental and social aspects: Xay, flood hazard mapping exercises will yield • Conduct of an environmental and social impact Blue-green measures for flood resilicience in Muang Xay important information. They will also help to assessment (ESIA) with associated sub-plans (ie. promote community flood hazard awareness; ESMMP, RAP) to IFC Performance standards • Support DOW to identify and implement • Implement flood risk management awareness raising once the proposed investment package has been moderate cost, locally appropriate retrofitted programs within communities and schools based on selected and detailed designs are complete. This flood mitigation and drainage control measures to programs already planned for the central level; and will ensure that a city-wide approach is considered existing infrastructure in waterways around the city; • Trial mobile applications for early warning and including the potential cumulative impacts from • Support villages to take ownership of riparian DRM data collection at the community level. other proposed investments such as the Lao- areas and establish dual purpose ‘green zones’ China railway and the ADB drainage project; (flood mitigation, visual amenity, production of • Development of site specific construction raw materials etc.) by incorporating ‘low cost’, environmental management and monitoring plans effective vegetative solutions such as vetiver grass. (CEMMP’s) for each of the proposed investments to manage and mitigate environmental impacts to the 56 Towards Urban Flood Resilience in Muang Xay aquatic ecosystem and the township environment; • Ensure that recommendations from the Gender Action Plan are incorporated into the next phase of the project; and • Development of environmental engineering guidelines to guide design and development of proposed investments and ensure compliance with CEMMP’s. It is believed that the implementation of the above recommendations will improve planning and coordination for urban planning and disaster risk management, increased flood resilience among local communities, a reduction in the threats posed by flood events for existing and planned infrastructure and positive outcomes for environmental and social management. 57 Towards Urban Flood Resilience in Muang Xay 58 Towards Urban Flood Resilience in Muang Xay REFERENCES • Dias, P., Arambepola, N.M.S.I., Weerasinghe, K., Weerasinghe, K.D.N., Wagenaar, D., Bouwer, L., Gehrels, H., 2017. Development of damage functions for flood risk assessment in the city of Colombo (Sri Lanka). 7th International Conference on Building Resilience, ICBR2017, 27-29 November, Bangkok, Thailand. • Finnegan, N.J. et al (2005): Controls on the channel width of rivers: Implications for modelling fluvial incision of bedrock. Geology. DOI: 10.1130/G21171.1 • Gash, J. H. C., I. R. Wright, and C. R. Lloyd (1979). Comparative estimates of interception loss from three coniferous forests in Great Britain. Journal of Hydrology, 48:89–105. • Killingtveit, Å and Sælthun, N. R., 1995: Hydropower development: Hydrology, Norwegian institute of Technology. • Lao Bureau of Statistics (2015). ‘Lao Population and Housing Census 2015’, Ministry of Planning and Investment, Lao Statistics Bureau, Vientiane, 2015. • MPWT (2017). ‘South East Asia Disaster Risk Management Project for Lao PDR: Environmental and Social Management Framework, last accessed 3 October 2017, available: https://www.mpwt.gov.la/en/projects-en/sea-drm • MPWT (2017). ‘South East Asia Disaster Risk Management Project for Lao PDR: Ethnic Groups Engagement Framework, last accessed 14 September June 2017, available: https://www.mpwt.gov.la/en/projects-en/sea-drm • MPWT (2017). ‘South East Asia Disaster Risk Management Project for Lao PDR: Resettlement Policy Framework’, last accessed 26 September June 2017, available: https://www.mpwt.gov.la/en/projects-en/sea-drm • Muang Xay Station (2017). ‘Weather and climate data from Muang Xay Station’, 12th July 2017. • Oudomxay Province Statistics Centre (2017). ‘Provincial statistics’, last accessed 26 June 2017, available: http://www.psc.gov.la • Vertessy, R.A. and H. Elsenbeer (1999) , “Distributed modelling of storm flow generation in an Amazonian rainforest catchment: effects of model parameterization,” Water Resources Research, vol. 35, no. 7, pp. 2173–2187, 1999. • World Bank, (2017). Project Appraisal Document for the Lao PDR SEA Disaster Risk Management Project, last accessed 1 October June 2017, available: https://www.mpwt.gov.la/en/projects-en/sea-drm • World Bank, MPWT (2016), Department of Waterways ‘Presentation on flood risk prevention and mitigation project in Oudomxay Province’. Background document. 59