Flood Hazard Index

FLOOD HAZARD MAP

The map below shows a flood hazard map that was generated using machine learning and the DEMSA2. Map A provides an overview of the Wilderness and Sedgefield areas in the Western Cape province of South Africa. One can see that large areas of these two settlements are at very high risk of flooding. In Wilderness (Map B), almost the entire Ebb-and-Flow Rest Camp and several holiday houses falls below the flood line, while in Sedgefield (Maps C and D) large parts of residential areas are at risk.

The DEMSA2 is ideal for flood hazard mapping as it has a high spatial resolution (2m) and vertical accuracy (about 50cm). This is in contrast to other digital elevation models (DEMs) such as the Shuttle Radar Topography Mission (SRTM) DEM that has a spatial resolution of 30m and a vertical accuracy of about 5m.

This set of maps is of particular value because the machine learning algorithm was trained using official flood line data (generated using hydraulic modelling) of other settlements. This allows for rapid flood hazard mapping in areas where no flood line data are available.