The Effects Of Land use Change On Erosioد & Flood In Saqqez basin Before & After Shahid Kazemi Dam Construction, Arc Swat model

One of the natural disasters that threatens people's lives and money today is the flood. The Basin of Saqez Chay, which enter to th through the Shahid Kazemi dam, has undergone many changes over the course of about half a century, and we have examined changes in its magnitude and its impact on erosion and flood. In this research, hydrometric data, sediment, soil, satellite images before and after the construction of the dam, topographic maps and geological data were used. After pre-processing satellite imagery, ENVI software was prepared for land use and NDVI maps. Then the data was entered into the Arc GIS environment, and the necessary maps and physiographic characteristics of the basin were prepared. . In the next step, soil data, flow rate, sediment, and Raster maps entered the SWAT software, and the information needed for simulation was obtained and after the simulation with the SWAT CUP, the results of the Validation and calibration were obtained. the Efficiency coefficient of Nash–Sutcliffe was 0.44 and the values of these coefficients were 0.76 and 0.68. For the Validation period, the Efficiency coefficient of Nash–Sutcliffe was 0.68 and the values of these coefficients were 0.86 and 0.67, respectively. Considering the amount of sediment and water flow, it can be said that the Basin is flooding. The closeness of observed data and simulation shows that the SWAT model works well for the basin. Finally, it was determined that agricultural land with dense pastures and rangelands decreased by 134.2 and 1944.19 respectively, and Wasteland and residential areas were, respectively 16.1617 and 2.7222 Percent to be decreased.