Comparison of remotely sensed water stages from LiDAR, topographic contours and SRTM

Digital elevation models (DEMs) are at the core of most environmental process modelling and disaster management. In flood inundation modelling, surface elevation constitutes one of the most important model boundary conditions. With the availability of high-precision DEMs (e.g. LiDAR) and globally available DEMs (e.g. SRTM InSAR) a big step seems to have been taken in terms of hydraulic modelling application or hydraulic information retrieval from such DEMs, with high potential in particular for ungauged basins. Comparative studies exist that report on both the validation of different remotely sensed elevation sources and their use for both hydrologic and hydraulic studies. To contribute to the existing literature on DEMs and hydraulic information, this study aims at comparing water stages derived from LiDAR, topographic contours and SRTM. A flood inundation model calibrated with distributed ground-surveyed high water marks is used to evaluate the remotely sensed water stages. The results show that, as expected, LiDAR derived water stages exhibit the lowest RMSE (0.35 m), followed by the contour DEM (0.7 m). A relatively good performance of the SRTM (1.07 m), which is possibly linked to the low-lying floodplain, suggests that the SRTM is a valuable source for initial vital flood information extraction in large, homogeneous floodplains. Subsequent 3D flood mapping from remotely sensed water stages confirms this but also indicates that flood mapping with low-resolution, low-precision surface elevation data is hardly possible on the small scale, as the accuracy of the resulting map depends too much on DEM uncertainties and errors both in the horizontal and vertical directions.