Medial Axis Approximation of River Networks for Catchment Area Delineation

The hydrological catchment areas are commonly extracted from digital elevation models (DEMs). The shortcoming is that computations for large areas are very time consuming and even may be impractical. Furthermore, the DEM may be inaccessible or in a poor quality. This chapter presents an algorithm to approximate the medial axis of river networks, which leads to catchment area delineation. We propose a modification to a Voronoi-based algorithm for medial axis extraction through labeling the sample points in order to automatically avoid appearing extraneous branches in the media axis. The proposed approach is used in a case study and the results are compared with a DEM-based method. The results illustrate that our method is stable, easy to implement and robust, even in the presence of significant noises and perturbations, and guarantees one polygon per catchment.