Distributed rainfall-runoff model incorporating channel extension and gridded digital maps

Models based on gridded maps provide a simple and flexible way of modelling hydrological processes at the catchment scale. Such a model is described for humid temperate regions where no regional aquifer is present. The catchment is represented by a grid of 50 x 50 m interconnected cells. These are characterized by the depth and porosity of the soil layer, the slope and direction of drainage, the possible presence of a stretch of river and the presence or absence of forest canopy. Three types of hydrological processes are modelled: throughflow (described by a modified version of Darcy's law); channel how (described by Manning's equation); and the interception-evaporation process as dependent on the presence or absence of forest canopy. The model predicts the hydrograph at the catchment outlet and the location of rivers in the catchment. These are compared with the observed river network, thus providing an additional means of assessing the model. (C) 1997 by John Wiley & Sons, Ltd.