Using Lidar Data to Evaluate Wetland Functions

The study objective is to extract HydroGeoMorphic Units in wetlands from LiDAR data estimating the required accuracy for assessing their functions in various hydrological and vegetation environments. Several Digital Terrain Models (DTMs) have been derived from LiDAR data with different point densities, ranging from 4 to 1 point/m2 with four interpolation methods. Then, the HGMU have been extracted from the more accurate DTM with an Object-based Image Analysis. This approach, validated with field data, has been applied in a study site located near the Mont-Saint-Michel, France. Results showed that the HGMU map quality highly depends primarily on the LIDAR data precision (point-density) and, in a lesser extent, on the interpolation method used. A minimum precision of 2 points per m2 was required to properly restitute the ditches network in wetlands and thus to evaluate their hydrological functions. The Nearest Neighbors interpolation provides best results and in the fastest computation time.