Mapping flooding hotspots

Floodplains that experience frequent floods, such as Narok town (Kenya), require the use of flood maps as a way to inculcate a flood forecasting system in the municipality. Satellite observations can record the river basin and terrain characteristics, but are too infrequent and coarse-grained to identify flooding hotspots. Eyes on the ground are needed to complete the picture.

Strathmore and TU Delft have developed a non-stationary hydrological model of the Enkare Narok river basin to analyze causes of flooding Narok town and identify flooding hotspots. Satellite observations are used as input to obtain a 30m resolution Digital Elevation Model and extract river properties and geometry. The DEM and river information feed into a model of the hydrological routing of the Enkare Narok river.

The model is a flexible tool to study floods in the river basin, including observed floods in Narok town. Yet it needs further validation on the ground, because the resolution and accuracy of the satellite information is insufficient for detailed predictions of flooding hotspots. Therefore the Strathmore team interviewed citizens living in the predicted flood areas, to specify and confirm flooding hotspots.

The 100-year flood map created in this endeavor is of great importance to Narok town and can help save lives. The implementation of an early warning system that is derived from the flood maps can reduce flood risk for the society as a whole by ensuring the preparedness of the citizens before the floods happen.

Graphical abstract

Figure: Narok town 100-year flood map


Mugwe, Olukuru and ten Veldhuis.  ” Flood Hazard Mapping using GIS in Kenya – A HEC-RAS Model Applied to Mapping the Enkare Narok River.”