Extraction of thalweg networks from DTMs: application to badlands

摘要

To study gully spatial patterns in the badlands using a continuous thalwegvector network, this paper presents methods to extract the badlands' thalwegnetwork from a regular grid digital terrain model (DTM) by combining terrainmorphology indices with a drainage algorithm. This method will delineate athalweg only where the DTM denotes a significant curvature with respect toDTM accuracy and relies on three major steps. First, discontinuous concaveareas were detected from the DTM using morphological criteria, either theplan curvature or the convergence index. Second, the concave areas wereconnected using a drainage algorithm, which provides a continuous, thick,tree-structured scheme. We assumed that these areas were physicallysignificant and corresponded to a gully floor. Finally, the thick path wasreduced to its main course and vectorised to obtain a thalweg network. Themethods were applied to both virtual and actual DTM cases. The actual casewas a LiDAR DTM of the Draix badlands in the French Alps. The obtainednetworks were quantitatively compared, both with a network obtained usingthe usual drainage area criteria and with a reference network mapped in thefield. The CI-based network showed the great potential for thalweg networkextraction.