Assessment of the hydraulic roughness of river flood plains using laser altimetry

Airborne laser altimetry is a promising new technique for rapid and detailed mapping of land surface topography and vegetation cover. The availability of laser scan data is expected to yield a great improvement in mapping and quantification of hydraulic roughness, which is needed for two-dimensional modelling of overbank flow. In this study, hydraulic roughness of flood plain vegetation was estimated using airborne laser scan data. Distributions of vegetation height and density were derived from the laser altimetry measurements using geo-statistical techniques. Raster maps of vegetation types and associated hydraulic roughness were obtained by combining the laser scan data with hydraulic characteristics of different vegetation types reported in the literature. The results were in good agreement with hydraulic roughness maps based on field observations of vegetation density and height.