Up-scaling surface runoff from plot to catchment scale

The main aims of this study were to identify and characterize the flow processes at the plot scale, and to up-scale these processes at the catchment scale by Terrain Analysis, using Digital Elevation Models (TauDEMs) based on in-situ sprinkling experiments. To calibrate the TauDEM-based method at the plot scale, in-situ sprinkling experiments were carried out on two plot scales (16 m² divided into 16 plots of 1 m² on various slopes). The marked differences in the textural and structural porosities between forest and grassland soil appear to control runoff processes. While grassland soils were characterized by a variable subsurface flow depending mainly on field slope, deep percolation was mainly found in forest soils. In addition, the map of flow directions also shows that two factors play an important role: on the one hand, the spatial sequence of the areas with a predisposition to surface runoff, and on the other, the tortuosity and length of channels that enhance the cumulative water volume in the target outlets. When based on sprinkling experiments, the TauDEM-based method provides more quantitative information on the dynamic of flow at the catchment scale. Furthermore, additional investigations are needed to validate the calculations of flow at a larger scale.