Abstract in English:
A mathematical "Sediment Yield" model has been developed and integrated with Rainfall-Runoff Model NAXOS  for estimating upland delivery rates of individual storm resulting from rainfall and runoff at the outlet of the catchment area of Wadi Surdud (2370 km2), Tihama, Yemen.
The erosion and sedimentation processes of the upland watersheds have to be assessed by means which do not rely on historical storm flow data. Methods that depend on available or measurable representative data were developed for a deterministic approach of the erosion process. Considering the present state of knowledge of the system analysis, GIS techniques offer a unique opportunity for the appraisal of the complex interactions of erosion and sedimentation factors (rainfall, runoff, watershed, physical and land use characteristics) as well as sediment load contributions of the upland watershed. To apply the model, the watershed is divided into 242 subwatersheds using TOPAZ (Topographic Parameterization) . Sediment yield is computed for each of 242 sub-basins using a steady state Sediment Continuity Equation  by routing mobilized sediment through a series of linear reservoir . The Model uses a mass balance equation to compute sediment transport, erosion and deposition over the land surface as direct throughfall, leaf drainage and streamflow. Sediment transport is considered as the erosion rate in the plane reduced by the deposition rate within the reach. The erosion occurs due to raindrop impact as well as surface shear. The model may serve as a tool for design of soil conservation measures.
The following results were obtained:
" Identification of hazard areas for soil erosion,
" Assessment of sediment transport at a given point within the basin,
" The basis for planning of soil conservation measures.
Keywords: erosion modeling; wadi Surdud; sediment yield, GIS