The use of digital elevation models for flood hazard mapping

Geomorphological processes that are active in floodplain areas are related to terrain elevation. The rate of sedimentation, as well as the texture and the quality of the deposited sediments, depend on the frequency of flooding and the sedimentary conditions during flood events. In addition to geomorphological and soil maps, digital elevation models may provide a sound base for quantitative studies of these processes: flood hazard and, in the case that historical elevation data are available, sedimentation and erosion rates may be derived from the digital representation of relief over space. This paper discusses the interpolation techniques and the test procedures that were used to compute a digital elevation model of a part of the floodplain area of the River Geul (the Netherlands). It was found that the fitting of mathematical splines outperforms local averaging and inverse distance weighting for estimating floodplain elevation. By means of the Digital Elevation Model and a long profile of the river, a flood hazard map was constructed. Photographs of a flood event were used for validation. Analysis of variance revealed that 57‐65 per cent of the variance in a set of data on flood‐related topsoil metal content can be accounted for by the flood hazard map.