Development Dialogue: Urban Flood Risk Management

Floods are undoubtedly the most frequent type of natural disasters, especially in the last 20 years during which flood events have become more dangerous, particularly for coastal cities and in peripheral areas of sprawling cities. Yet, although climate change may contribute to weather extremes, many coastal cities are still more exposed to flooding due to poor ground water management rather than from rising sea level. More population density in urban areas also means that exposure of assets and settlements widens especially with poorly managed urbanization (clogged drains, unregulated spatial expansion, inadequate housing). At a household level, the impact of floods also exacerbates the hardships of the urban poor as it amplifies their vulnerability through water-borne diseases, lower nutrition, less education possibilities and disrupted sources of livelihoods.

Even if it is impossible to completely eliminate flood risk (even in highly resilient countries), far more still needs to be done by policy-makers to better understand, effectively manage existing risks and anticipate future hazards. The good news is that, in spite of rapidly urbanizing countries, the toolbox of flood risk management measures has never been as comprehensive and innovative as before, and is becoming increasingly multidisciplinary and flexible.

Join development leaders, expert practitioners and policy-makers during this thought-provoking two-week online forum to discuss how we can better design, implement and integrate different approaches to urban flood risk management, and ensure that cities and towns in the future are more informed, better equipped and sufficiently prepared to face natural disasters such as floods.


Junaid Ahmad is the Senior Director for the Water Global Practice, World Bank GroupModerator.

A Bangladeshi national, he leads the Water Global Practice (GP), which supports governments to build a water-secure world for all. The Water GP focuses on improvement of water resources management and delivery of services in a context of water in the broader economy. Junaid takes on this role following his position as Director for Sustainable Development in the Middle East and North Africa Region, a position he held from 2012-2014. Junaid joined the World Bank as a Young Professional in 1991, working as an Economist in Africa and Eastern Europe before joining the Africa Infrastructure Unit. He spent 10 years in the field, first as the Deputy Resident Representative and Principal Economist in South Africa, and then as Regional Team Leader of the Water and Sanitation Program for the South Asia region based in India. He later became Sector Manager for Social Development for the South Asia region and subsequently for Urban Water and Sanitation before taking on the latter responsibility across the Africa region in 2010. He was a team member of the 2004 World Development Report (WDR): Making Services Work for Poor People.

Junaid brings a strong track record of management and leadership in the area of service delivery, combining intellectual and analytical rigor with strategic operational focus. Recognizing that reform in the water sector can rarely be addressed in isolation, he has championed the cause of the sector through local governments, communities and the private sector. Focusing on institutional reform, Junaid has taken an inter-sectoral approach to water, linking the sector to important drivers of change such as decentralization, regional cooperation, and climate change.

He holds a PhD in Applied Economics from Stanford University, an MPA from Harvard University, and a BA in Economics from Brown University.

Junaid: Urbanization and climate change are, independent of each other, two of the toughest challenges we are facing this century. And the impact of them combined makes cities often vulnerable to disasters, endangering efforts to eradicate poverty. Floods are the most frequent among all natural disasters and the urban poor are disproportionally affected by the economic and social impacts.

Often the solution of flooding is thought to lie within the cities but that may be a too narrow view of the issue. We may need a far more integrated approach – taking a broader basin-wide approach – to establish effective mitigation measures and manage water sustainably to reduce the risk of urban flooding in the long-term.

The World Bank is working across various sectors to advance knowledge on water-related disaster management, bringing both soft and hard solutions to the table. However, no single partner can do it alone. We are excited to engage in this interactive online discussion which is bringing together experts, practitioners, and policymakers from all over the world.

We invite you to ask questions, to raise issues, and to share your experiences and innovative solutions in managing urban flood risk.

We look forward to a thought-provoking discussion!


Kees Bons, specialist advisor, Deltares, on adaptation and climate proofing.

Kees Bons, specialist advisor at Deltares, is an experienced environmental hydrologist and manager who can rely on a sound background in hydrology and earth sciences. His research experience in both surface and groundwater hydrology forms a good foundation for the integrated approach to solving water management problems, which has been his key occupation. 

He addressed all aspects of water balance and distribution, flood risk reduction, pollution load estimation and calculation, transport of pollutants through the river system, and water quality processes. His key qualifications relate to the analysis of the natural system and its relation with human activities, the translation thereof into mathematical models, the analysis of cause and effect relationships regarding environmental aspects, and the set-up and implementation of water management information systems. 

Kees Bons was involved in many projects related to National Water Resources policy development and monitoring, data presentation and analysis. This concerned also the update of monitoring systems for the Water Framework Directive (WFD). Besides his European experience, Kees Bons has five years experience in the Arid zone (National Water Resources Plan Egypt) in water quality planning and monitoring in addition to several months in Botswana and Saudi Arabia and many years experience in the tropics (Indonesia) regarding integral impact assessment of forestry activities and recently Strategic Planning of the Coastal Flood Defense and Improved Water Sector Planning, Management and Development.

From 2003 and 2007 Kees Bons was the director of the Inland Water Systems Unit of WL | Delft Hydraulics. With the merger into Deltares he became director of the new Scenarios and Policy Analysis Unit focusing on policy development and IWRM. Since 2010 he managed the Unit Subsurface and Groundwater systems. His management experience makes him an effective Project manager with a broad international experience. In 2012 he was appointed as specialist advisor for South East Asia and Deltares’ representative in Indonesia.

Kees: One strategy for climate proofing a certain area with respect to a certain impact is the adaptation tipping points approach. Adaptation tipping points are points where the magnitude of change due to climate change or sea level rise is such that the current strategy will no longer be able to meet the objectives. This helps policy makers know whether or when a water management strategy may fail and what alternative strategies are needed.

In this approach, the time window of an adaptation tipping point will define when an alternative, adaptive strategy will be needed. This assumes that climate change is the main driver of adaptation, but this method is just as relevant for other drivers for change, such as population growth or subsidence. In urban areas, however, the ‘normal’ maintenance, modification or renewal of infrastructure, buildings and public spaces could provide an opportunity for adaptation, for instance to reconsider the existing urban drainage (storm water) system from a different standpoint.

Many adaptation responses can be implemented in conjunction with normal maintenance, modification and renewal cycles and with minimal additional cost, such as with sewer rehabilitation, urban greening and neighborhood regeneration projects. From this perspective, the normal dynamics of the urban area should be recognized and used as a driver of adaptation.

The mainstreaming method has been developed as an extension to the adaptation tipping points approach by anticipating adaptation opportunities in the normal dynamics of urban areas. Mainstreaming adaptation of urban drainage systems to climate change is expected to lead to potential cost reductions, since adaptation options can be integrated into the infrastructure and building designs at an early stage instead of being applied separately.


Adri Verwey, Consultant, on the principal factors contributing to urban flooding becoming an increased risk world wide.

Adri Verwey is working as a consultant to the World Bank with current and recent assignments in Poland (investment over 1 billion Euro), Croatia, Mozambique and Brazil. He has broad experience in river and urban flood management through consultancy projects and through fundamental research and software development. During the Bangkok flood disaster of 2011 he worked for 6 weeks at the Flood Crisis Centre. Activities included field inspections and the development and application of a flood model to study the flood propagation in and around Bangkok. On this basis he advised the Thai Minister of Science and Technology Plodprasop, Army Chief Worapong Sanganet and Prime Minister Yingluck Shinawatra on emergency flood management operations. He has also been playing a leading role in the development of drainage master plans for (parts of) large cities, such as Hong Kong, Ho Chi Minh City, Singapore, Beira and São Paulo.

Adri Verwey has played a key role in software development for hydraulic engineering applications, including the modelling systems MIKE 11 and SOBEK. With an employment record including DHI, UNESCO-IHE and Deltares, he has built up extensive experience with water related problems in countries world wide, such as The Netherlands, Thailand, Hong Kong, Singapore, Vietnam, India, Sri Lanka, Bangladesh, Korea, China, Taiwan, Turkey, Yemen, Australia, New Zealand, United States, Guatemala, Costa Rica, Brazil, Venezuela, Argentina, France, Portugal, Sweden, Czech Republic, Slovakia, Poland, Mozambique, Morocco, and Egypt. 

He published many articles on the development and application of mathematical models with focus on hydraulic engineering and hydrology. Mr. Verwey is one of the authors of the widely referenced book “Practical Aspects of Computational River Hydraulics”. He was the Principal Organiser of the First International Conference on Hydroinformatics, held in Delft in 1994.

Adri: It is indeed true that urban flooding is becoming an increasing risk world wide. The principal factors contributing to this increased risk are:

  • Reduction of drainage capacity in existing systems. There is a tendency to occupy more and more the drainage channel capacity in existing cities. With the expansion of cities and increased economic development, traffic capacities have to be expanded. With lack of space in the cities the easiest way out is often to claim the space available for urban drainage.
  • Lack of planning in urban expansion. When cities are expanding it is extremely important to develop master plans for the expansion of the cities before concessions are given to private or corporate project developers. When cities are expanding, not only there is a need to construct proper drainage facilities for these new areas. Existing urban areas are usually affected as well and the overall drainage capacity may be well under-designed for the new situation. I have come across situations where land was sold for urban expansion without attention being given to drainage and road access infrastructure provided at all.
  • Lack of insight into the processes of urban drainage. Although during extreme storm events rainfall is not distributed uniformly over cities, the most extreme events bring rainfall all over the place. In such situations it is wise to delay the runoff from upstream areas in the urban catchments and to speed up runoff in the downstream parts. In this way, the runoff hydrograph is prolonged in time, with a reduction of the peak flow as a consequence. This is the reason why the concept of “Sustainable Urban Drainage Systems" (SUDS) was introduced. One misconception that has to be mentioned here is that the importance of SUDS is not primarily in increasing the infiltration of rainwater into the soil. The most important aspect is the reduction in speed of runoff. In any case, SUDS concepts are most effective in the upstream parts of urban drainage systems.
  • Neglected maintenance. This is one of the principal factors contributing to the problem of urban flooding. This problem relates to the lack of dredging of drainage canals and the lack of maintenance of hydraulic structures.
  • Climate change aspects. Many of the problems of urban flooding are attributed to Climate Change. However, most of the time the problems have to be attributed to the reasons given above. It is true that sea levels at the outlets of drainage systems are increasing and that at many places in the world the rainfall intensities are increasing. However, this is a relatively slow process, which will produce real impacts only a few decades from now. It is my own experience that properly designed changes in the drainage system (demonstrated by using simulation models) will prepare the city against urban flooding problems for many decades to come.


Yoshio Tokunaga, Chief Researcher for the International Centre for Water Hazard and Risk Management (ICHARM), Japan on Japan's experience in flood risk management. 

Yoshio has a wealth of experience in water hazard and risk management.  He started his career as national government official at Ministry of Land, Infrastructure, Transportation and Tourisms (MLIT) in 1990’s, and has been leading various units such as head of Yamatosaka Dam Project of MLIT,  Water Resources Planning of MLIT, Planning division of Japan Dam Engineering Center, River Bureau and Reconstruction Bureau of Ministry of Construction (which was merged as Ministry of Land, Infrastructure, Transportation and Tourism in 2001) etc. 

He has rich experiences in the international arena as well and has extensive experiences such as serving as Disaster Management policy Advisor for the Indonesian National Disaster management Agency in Indonesia from 2010 to 2014, as well as Team Leader of JICA Flood Control and Sabo Project for Department of Public Works and Highways in the Philippines.  He has contributed in planning and presenting as a reepresentative of Japan at the International Disaster Relief Excursive in Padan, Indonesia in 2013-2014, involved in socialization and education projects for the natural dam in Way Ela River in 2012-2014 etc.  He also promoted the establishment of platform “Japan Indonesia Disaster Management at Local Level” in 2011-2013. 

At this current position at ICHARM, the global centre of excellence for water hazard and risk management, he has been focused in disaster management and dam engineering, and contributing as one of the leading researchers in the area of innovative research, effective capacity building and efficient information network for ICHARM to keep serving as a knowledge hub for best national and local practices and an advisor in policy making.

Yoshio: While I was working in Southeast Asian countries, I saw many small houses built along rivers, which was dangerous in time of flood in some mega cities. I also went to urban areas in which river flow conditions changed and flood risk became higher because their upstream areas had developed quickly.

I am very glad to be invited to this dialog and given opportunities to introduce Japan’s experience in flood risk management.

About 50 years ago, Japan experienced a high economic growth era and many cities urbanized quickly. Since then, water-related problems have emerged and various countermeasures have been carried out. For instance, non-structural measures are: flood fighting activities by residents, offering water-level and warning information for flood fighting efforts and evacuation, making hazard maps, and conducting evacuation training with various kinds of groups like residents, schools, and municipalities and so on. Recently on-site displays of inundation levels have been put in place, and X-Band radars for real-time observation of localized torrential rainfall have been installed.

Japan also has a long history of taking structural measures for flood control: for instance, constructing flood ways such as the Arakawa River (completed in 1930), removing illegal settlements in river areas, implementing river channel improvement works, constructing gates and dams for flood control. More recent efforts include underground discharge tunnels and high-standard embankments. Also considered effective are comprehensive flood control measures in river basins, such as construction of flood retention ponds and rainwater storage facilities in open spaces of schools and apartment complexes and installation of infiltration facilities.

For high flood-risk urban cities in the world, I think that it is important 1) to understand conditions related to flood risk accurately, 2) to address flood risk management with a long-term perspective, and 3) to share information on risk management with all stakeholders.

Ede Ijassz-Vasquez, is the Senior Director for the Social, Urban, Rural and Resilience Global Practice, World Bank Group, Moderator.

He leads a team of more than 600 technical experts deployed across the world, leveraging global knowledge and collaborating with partners to help tackle development challenges in: (i) social inclusion and sustainability; (ii) mainstreaming resilience; (iii) territorial and rural development; and (iv) urban planning, services and institutions. Previously, he was the Director for Sustainable Development, Latin America and Caribbean Region where he oversaw a portfolio of about $ 17,000 million. From 2007 to 2011, he was based in Beijing, where he managed the Sustainable Development Unit for China and Mongolia. Earlier in his career, he managed the global trust-funded programs ESMAP and WSP in energy and water and sanitation. He has a Ph.D. and a M.Sc. from the Massachusetts Institute of Technology (MIT) in civil and environmental engineering, specializing in hydrology and water resources.


Ede: For the first time in history, the majority the world’s population now lives in cities.  And this pattern is not going to dissipate in the coming years: it is expected that by 2050, 70% of the world’s population will be urban dwellers, turning cities into even larger hubs of development and growth.

The bad news is that poorly managed urbanization inevitably increases flood impacts. Sprawling megacities such as Jakarta, Dakar, Brisbane, Bangkok, or Mumbai have recently been associated with damaging floods, often with complicated socio-economic repercussions and heavy death toll. The good news is that, in spite of rapid urbanization, the toolbox to address flood risks has never been as comprehensive and innovative as before, and is becoming increasingly multidisciplinary and community-orientated.

But, context matters: every flood risk scenario is and will be different. This also means that understanding type, source and probability of flood events, and mapping out exposed assets and the level of vulnerability of a given population are important foundations from which decision-makers can benefit in order to identify (and justify) the appropriate mix of interventions. The most pressing challenge then becomes implementing the “right” combination of structural and non-structural measures, which are taken as a whole, need to be relatively robust to face uncertainty and also sufficiently adaptive to many flooding scenarios under conditions of climate change.

Such measures vary in scope and in scale, and can include flood risk modeling to enhance planning and early warning systems in Indonesia, integrating structural measures with information management systems in the Philippines, improving solid waste management systems to avoid clogged draining in Sri Lanka, or linking risk-informed land use planning with early recovery activities in India.  In the long term, to decrease flood impact and ensure that infrastructure and institutions are as responsive as possible, it is necessary to strengthen hazard monitoring, and integrate forecasting and early warning systems with comprehensive emergency management systems. In regions frequently affected by disasters, relying on fiscal resilience mechanisms (contingency planning, risks transfer mechanisms, parametric insurance solutions) becomes necessary to reduce shocks and provide cost-effective solutions.

This is why the World Bank Group in partnership with the Global Facility for Disaster Reduction and Recovery (GFDRR) is convening during the next two weeks this important online conversation to promote Urban Floods Risk Management.

New Question
What are the most effective quick impact solutions which can drastically minimize damages and losses from flooding?