The impact of environmental change and land management on the hydrology of a rural Mediterranean catchment

摘要

The purposes of this study of the Roujan basin Southern France (1 km~2) are first to assess the role of human impact on the basin hydrology especially the importance of the role of terraces and ditches network. For that a spatially distributed hydrologic model linked toa Geographical Information System (GIS) was developed. GIS, here Arc/Info, is used to manipulate spatial data such as Digital Elevation Models (DEM), soils map, channel network, topography and landcover and to divide the basin into hydrological units. Runoff from each unit is estimated using a deterministic model based on the ponding-time algorithm and then routed throgh the ditches network using the diffusive wave equation, to the downstream outlet to give the full hydrograph. Two scenarios were compared and analysed. The first one uses the actual drainage network formed by man made ditches and the second one studies the impact of land abandonment accompanied with the disappearance of ditches network and the appearacnce of the antural drainage network. Results shows the importance of the role of ditches network and agricultural terraces on the form of hydrograph, the lag time and the maximum discharge.