Development of an Integrated Method for Studying the Effects of Large Dam on Erosion, Length and Width of River

For protection of river banks, simulation of lateral velocity and shear stress distribution is necessary in river bends. Using usual methods for preparation of soil erosion resistance map is very time-consuming and expensive. Therefore, using GIS and RS can improve usual methods for this purpose. Preparation of soil erosion resistance maps by GIS and RS is an exact, rapid and economic method for collection of spatial data and making decision. In this research an integrated method was developed based on critical shear stress for incipient motion of sediment particles. Changes in the geometry of the Karkheh river within 40 km reach downstream of Pay-e-Pol hydrometric station was determinedand hydraulic parameters and the shear stress were calculated by CCHE2D model. Erodible reach was located at 30 to 35 km downstream of Pay-e-Pol hydrometric station before construction of dam. After construction of dam this reach moved to 25 to 32 Km downstream of Pay-e-Pol hydrometric station (this reach has transferred to upstream). Before construction of the dam, the length of erodible reach was 1314 m (3.3% of the total reach) and after construction of the dam this length decreased to 840 m (2% of the total of reach). Therefore, the length of erodible reach was reduced approximately by 1% due to the construction of dam.