In this case study, an approach for finding regions endangered by extreme rain is presented. The approach is based on the assumption that sinks in the surface are more endangered than their surroundings. The surface data, which are the source for the classification, are generated using a Cartosat stereo scene. The classification is performed by using an algorithm for retrieving the terrain positioning index. Different classification schemes are possible, therefore a set of input parameters is iteratively computed. The classification results are then evaluated. For validating the classification stock data of an insurance are used. We compare the position of the reported damages caused by extreme rain with our classification. By doing so we got the confirmation of the assumption.