Influence of surface roughness in hydrological response of semiarid catchments

Here, an investigation has been carried out in order to understand the influence of the surface roughness in the definition of the hydrological response of semiarid catchments. Following a previous study of one of the authors, a modified version of TOPMODEL is used, in which the convolution routing procedure has been extended to the hillslopes by specifying the routing velocity for each pixel of the watershed. These velocities have been linked to the watershed land use through the different surface roughness whose coefficients has been derived on the basis of Engmanʹs table. In this paper, roughness coefficient distributions are expressed as function of a unique value treated as a calibration parameter. An analysis of model response in terms of prediction has been made for each roughness coefficient distributions using the GLUE procedure. Results from the application of the modified version of TOPMODEL in a Mediterranean experimental catchment located in Sicily are presented and discussed.