Estimate of Erosion and Sedimentation in Semi-arid Basin using Empirical Models of Erosion Potential within a Geographic Information System

Abstract

This research is aimed at predicting erosion and sedimentation in the Ghareh Aghach Basin in the central part of Iran using Erosion Potential Model (EPM) models incorporated into Geographic Information System (GIS) software. This basin has an area of about 8955 hectares. The region has a range of vegetation, geological, soil texture and land use types. The basin was subdivided into 5 sub-basins. Data required for this study were collected in part through published reports, whilst the remaining was derived by field surveys. Necessary maps in EPM models were prepared in Autocad-2006 medium and were transported to IILWIS, after some revision. After constructing topologies for all polygons, we entered weightings for all layers within the Arc-View software. Combinations of all layers were managed thereafter. Coefficient of each factor was determined, and erosion intensity coefficient (Z) was calculated. Four layers for EPM model were combined to develop the final layer of erosion and sedimentation. The results of the EPM model for homogenous and uniform sampling units showed that 0.19% (16.7 ha) of the total watershed area were classified as class I of erosion category with very low sedimentation and 15.1% (1352 ha) were classified as class II of erosion category with low sedimentation and 41.3% (3699 ha) were classified as class III of erosion category with medium sedimentation and 13.2% (1175 ha) were classified as class IV of erosion category with high sedimentation and finally 30.2% (2711 ha) were classified at class V of erosion category with very high sedimentation, respectively. The result of comparing erosion and sediment values using an EPM model with measured values showed that no significant difference was observed between the estimated and measured values ( P < 0.05).