Laser altimetry and hydraulic roughness of vegetation : further studies using ground truth

Elevation measurements were carried out in the Duursche Waarden (river IJssel) and Afferdensche and Deestsche Waarden (river Waal) using an airborne laser altimeter. Ground truth data were collected for vegetation characteristics in both floodplain areas. The objective was to explore the applicability of laser altimetry. The vegetation characteristics that were analysed are the vegetation height, the average stem diameter and the number of stems per m2, which together determine the blockage area per unit area. All information was used to generate maps of the hydraulic roughness under design discharge conditions, estimated on the basis of the laser scan data.