Abstract
It is quite difficult to model soil erosion and sediment transport at regional scales using coarser grid size (1 km) due to slope averaging and land-use averaging effects. To cater the problem, a process-based soil erosion and sediment transport modeling strategy has been developed to estimate the soil erosion, deposition, transport and sediment yield at regional scale. The catchment's spatial variability is modeled as a regular square grid system with canopy interception, infiltration, depression storage, one-dimensional overland flow and sediment transport in the steepest descent direction. The overland flow is modeled as the equivalent channels, which may represent the cumulative width of all rills and gullies in each grid. The fraction of the ponded surface is determined on the basis of the flow accumulation value of the each grid, grid size and its land use type. The soil erosion processes are modeled as the detachment of soil by the raindrop impact over the entire grid and detachment of soil due to overland flow only within the equivalent channels, whereas sediment is routed to the forward grid considering the transport capacity of the flow and the existing sediment load. The slope averaging effect is taken care by adapting a Fractal analysis approach. The model has been calibrated for Nan river basin (N.13A) and applied to the Yom river basin (Y.6) and Nam Mae Klang river basin (P.24A) of Thailand, simulated results show good agreements with the observed sediment discharge data.
