برآورد رسوبدهي به كمك SPANS-GIS

Prediction of sediment yeild using SPANS - G1S

This article presents the promising tool lor the prediction of water erosion in the areas where availability of hydrological data is limited. The modeling includes the integration of MUSLE with SPANS-GIS for semi-arid zones particularly Syahrood one of the sub-basins of Damavand watershed in Iran where soil erosion by water is one of the land-related problems. Runoff erosivity, soil erodibility, slope length, slope steepness, cover management, and erosion control practice factors were computed and included in the digitized and computed Thiessen polygon, land component, slope and land-use maps of the watershed. The amount of sediment yield in each land-use was computed by overlaying these maps with the appropriate models in the SPANS-GIS. The result shows higher erosion rates are related to drylands that usually belong to steep slopes and are cultivated in rows parallel to the slope direction. The average sediment yield for the entire study area was 745 t/km2.yr with the higher and lower erosion rates of 978 and 221 t\km.gr2 in the drylands and orchards, respectively. This sub-basin is characterized with the lack of recorded rain gauge data, which limited the application of commonly used erosion models. Results demonstrated that interfacing MUSLE with a GIS in an effective method for the prediction of soil erosion in small watersheds with limited data sets. A GIS simplifies the extracting of necessary fators from databases. SPANS-GIS uses quadtree data model that provides compact raster representation by using a variable - sized grid cell, useful for having least file size when the data are relatively homogeneous and do not require frequent updating.