Extraction and analysis of the structure of a drainage network from Digital Elevation Models

A new algorithm, for the removal of Digital Elevation Models errors especially developed for depressions and flat areas, is presented then applied to extract drainage network. The algorithm uses neighbourhood techniques as well as iterative spatial techniques that depends on a threshold : the maximum area of depression zone. This method was used to delineate catchment boundaries, to extract drainage network and to examine the geomorphology of twelve basins having their outlet in the Mediterranean sea in the Languedoc-Roussillon region southern France. The sensitivity of the model was analysed then the fractal geometry was used to analyse morphometric and scaling properties. The use of fractals allows to point out self-similarity in the structure of channel networks and to define new catchment shape indexes useful for comparing catchments.