Modelling surface and underground streams in drainage network computation

Drainage networks can be computed from high-resolution digital elevation models derived from airborne lidar point clouds. However, before mapping the streams, drainage enforcement must be applied to alter the model and remove local depressions that can interrupt the computed flow. This includes carving the terrain at culvert locations to direct flows under roads embankment. This operation remains approximate and leads to more alterations of the terrain.This work is part of a project that aims to integrate culverts into the calculation of the drainage network. This would allow for the inclusion of underground components, without altering the DEM or requiring manual intervention. The paper presents a new conceptual model that describes the drainage network, including both surface and underground streams, and drainage basins with their divides and provides a richer description of the drainage. Preliminary results are also presented in a case study.