Flood risk mapping

Flood risk maps are the essential tools for land use planning in flood-prone areas. The basic criteria for mapping are usually chosen according to flood return periods. Sometimes, the expected water depth or dynamic considerations are used instead. These criteria are discussed on mapping examples from several countries. To draw a flood risk map, four phases are usually recognized: hydrologic, geomorphic, hydraulic and land use. Each of these phases poses different problems and requires relevant methodologies to accomplish them. As an example, the program for flood risk mapping of the Valencia Region in Spain is presented. A flood risk map is considered as a preliminary yet necessary initial step for all regional development policies.