A Guide to Integrated Urban Flood Risk Management for the 21st Century

Cities and Flooding
KEY FINDINGS Floods are the most frequent among all natural disasters, causing widespread devastation, economic damages and loss of human lives. The East Asia and Pacific region is particularly vulnerable: In the past 30 years, the number of floods in Asia amounted to about 40% of the total worldwide. Urban flooding is becoming increasingly costly and difficult to manage as low- and middle income countries in the region transition to largely urban societies, with a greater concentration of people and assets in urban centers. In addition to direct economic damage, floods have long-term consequences such as loss of education opportunities, disease and reduced nutrition which may erode development goals. Rapid urbanization creates poorer neighborhoods which lack adequate housing, infrastructure and services, making the poor more vulnerable to floods, especially women and children. The most effective way to manage flood risk is to take an integrated approach which combines structural and non-structural measures. This includes: Building drainage channels and floodways; Incorporating “urban greening” such as wetlands and environmental buffers; Creating flood warning systems; and Land use planning for flood avoidance. The key is getting the balance right, because current risks may change in the future as the effects of urbanization and climate change accelerate, requiring flexible solutions. Various aspects of the impact of these measures need to be considered, including environmental degradation, biodiversity, equity, social capital and other potential trade-offs. Successful flood risk management requires robust decision making, with greater coordination between different levels of government, public sector agencies, civil society, educational and private sectors among others. Tools such as flood hazard maps as well as simulation and visualization techniques can help decision makers better understand flood risk and its hazards, predict outcomes and assess costs. Communications also plays a significant role in raising awareness and reinforcing preparedness. The guidebook warns that less severe disasters can be forgotten in less than three years. As flood risk cannot be eliminated entirely, planning for a speedy recovery is also necessary, using reconstruction as an opportunity to build safer and stronger communities which have the capacity to withstand flooding better in the future.