Topology is usually managed in DEM software as near-field or vicinity topology. The method discussed here is related to the use of tree and graph structure to manage long-range topology. The use of n-ary tree structure is first presented. This n-ary tree structure is applied to compute a monodirectionnal drainage model. This tree structure is then used to compute the drainage tree of cachments and sub-cachments, watersheds contours and to process variables that are imported in the DEM through rastering procedures. The use of graph structures is then presented to manage multidirectionnal drainage model. The main use of this graph structure is in the field of estimation of the Beven-Kirkby index which is then applied to extract contours of waterlogged bottom lands.
Key words : tree structure, graph structure, digital elevation model, topology, topographic index
Short title : Tree and graph structures in DEM
