Mapping Forested Floodplain Topography Using InSAR and Radar Altimetry

Abstract

An accurate floodplain digital elevation model (DEM) is an essential input for the hydraulic modeling of water flows across the floodplain. A method combining interferometric synthetic aperture radar (InSAR) and radar altimetry is presented to derive the bare-earth topography for a forested floodplain with an improved accuracy. This method is applied to the floodplains associated with the middle reach of the Congo River in Central Africa. The floodplain topographic model was evaluated using Ice, Cloud, and land Elevation Satellite (ICESat) altimetry measurements, and the root mean squared error (RMSE) was estimated to be 2.71 m. The newly-created elevation model has shown improvements in capturing subtle elevation variations within the forested floodplain, compared with two other vegetation bias corrected DEMs—the multierror-removed improved-terrain DEM (RMSE of 4.95 m) and the Bare-Earth’ SRTM (BEST) DEM (RMSE of 3.32 m). We were unable to generate a DEM for the entirety of the floodplain due to missing InSAR and radar altimetry data. This could be a problem for the DEM's integration into hydraulic modeling workflows where the elevation model would need to be merged with ancillary elevation products. This could lead to inconsistencies in the merged DEM and the subsequent modeled outputs. However, it is expected that future L-band SAR and satellite altimetry missions can remedy the data gaps and provide a more robust spatial coverage.