Cities and Flooding: A Guide to Integrated Urban Flood Risk Management for the 21st Century

February 21, 2012

  • 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.