RAINFALL-RUNOFF MODELING OF PARTLY URBANIZED WATERSHEDS - COMPARISON BETWEEN AND DISTRIBUTED MODEL USING GIS AND OTHER MODELS SENSITIVITY ANALYSIS

This paper presents an original integrated approach to rainfall-runoff modelling for partly urbanized watersheds. A digital terrain model (D TM), allowing use of GIS techniques, was built not only for representi ng the undeveloped part of the catchment but also the urbanized area. For each cell of the DTM grid, a water budget is computed, providing r unoff and interflow amounts. The water volumes generated at each cell are moved along the steepest slopes with a celerity depending on this slope, until they reach the outlet and contribute to the resulting hyd rograph. The model was tested in a partly urbanized catchment, special ly equipped with rain and flow measurement station. Comparisons with o ther procedures, mainly with SWMM and WALLRUS models, shows that the p roposed model seems to be one of the most accurate. Moreover, the sens itivity analysis confirms the flexibility of the tool. Its concept, ba sed on GIS routines, allows much of the computation to be done automat ically, avoiding a lot of tedious tasks. For example, it becomes relat ively easy to check the consequences of urban planning options.