Application of a distributed GIS model for studying surface runoff processes in an urban wetland

The Woluwe is a small river that drains an area of 9400 hectares in the Belgian part of the Scheldt basin. The central part of the Woluwe River flows partially through several park and pond systems of the Brussels agglomeration. Within the Woluwe catchment there are drinking water wells, wetlands in seepage zones and 21 ponds with different functions (water storage, fish-stock, recreational fishing, boating, ornamental parks, wetland nature value). In urban catchments, surface runoff is the most important process that determines the water quantity and quality. An analysis of potential differences in runoff generation, influenced by land-use changes in the catchment, could provide information on the future hydrological state of the urban wetlands. Similarly, an evaluation of the runoff partitions from different land-uses could show the possible source of water pollution in urban wetlands. A distributed modelling approach, on basis of the WetSpa model and supported by remotely sensed data, was used for studying runoff in the Upper Woluwe catchment. WetSpa is a GIS grid-based distributed hydrological model that simulate with an hourly time step peak discharges, hydrographs and the spatial distribution of runoff, infiltration and evapotranspiration. The WetSpa model is applied to analyze the effects of topography, soil type, and land-use on the flood characteristics. More specifically, the assessment of imperviousness estimated on basis of remote sensing and its influences on runoff generation are described. © 2007 Taylor & Francis Group.status: publishe