Quantitative Mapping of Hydrodynamic Vegetation Density of Floodplain Forests Using Airborne Laser Scanning

The determination of hydrodynamic vegetation density of floodplain forests in the Netherlands is currently based on manually delineated vegetation types and a lookup table to convert these into vegetation density. In this paper a method is presented to extract vegetation density from high-density airborne laser scanner data. Field reference data were collected on 45 plots in three different floodplains in the Rhine delta. Two predictors for vegetation density were extracted from the laser data: (1) percentage (P) of points in the height interval inundated by the water, and (2) a vegetation area index (VAI) that corrects for occlusions from the crown area. A computer simulation, using a digital forest model, was carried out to gain more insight in the prediction of vegetation density from laser scanning data. The simulation showed the need for a minimum number of points to accurately compute the predictors and the sensitivity of the predictors for non-returned ground points. P proved the best predictor of vegetation density (R = 0.62).