Flood hazard maps have to be developed for areas, which have been identified in the preliminary flood risk assessment. For certain flood frequencies the extent and the water depth, the flow velocity or the relevant water flow have to be mapped. Flood frequencies consider (2007/60/EC):
- floods with a low probability, or extreme event scenarios;
- floods with a medium probability (likely return period ≥ 100 years);
- floods with a high probability, where appropriate.