Understanding Flood Hazard

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This chapter addresses some of the most fundamental questions asked by those who need to understand the flood risk faced by their cities and towns: Where is the flooding coming from? How severe is it? How frequent will the flooding be? Is it going to be much worse in the future?

Key messages

  • Understanding the type and source of flooding are both essential if the appropriate flood risk reduction measures are to be identified.
  • The tools and models used to assess and forecast flood hazard are invaluable in planning and operationalizing flood risk reduction measures.
  • Even the best flood models and climate predictions result in a large measure of uncertainty. Flood risk managers must therefore consider measures that are robust to uncertainty and to different flooding scenarios.

Tools and guidelines

  • Data requirements for flood hazard assessment
  • How to prepare a flood hazard map (Riverine)
  • How to prepare a flood hazard map in the coastal zone
  • Considerations in designing a flood forecasting system
  • Examples of flood forecasting and early warning systems
     

Case Studies

1.1: Floods in Southern China

1.2: Spatial analysis of natural hazards and climate variability risks in the peri-urban areas of Dakar, Senegal

1.3: Flood forecasting in India: a web-based system (WISDOM)

1.4: Mekong River Commission: Mekong Flood Forecast

1.5: The Tropical Rainfall Measuring Mission (TRMM)

1.6: Climate-proofing road infrastructure in Kosrae, Federated States of Micronesia

1.7: A megacity in a changing climate, Kolkata, India

1.8: Mexico City’s response to climate change and variability