Prediction of Bank Erosion in Kashkan River Meanders

Kashkan River is one of the important and water logged tributaries of Karkheh River which collects waters of a vast area of ​​Lorestan province. This river at the south-west part of Poldokhtar in a region known as the Gel-Sefid River is joined to Seymare River and creates Karkheh River. Length of Kashkan river is about 270km، and the water basin area of this river at upstream of Kashkan - Poledokhtar station is 9400 km2. This river due to its morphological and meandering characteristics and even in some floodplain points is arterial. There exists the problem of side erosion and displacement of river plan. Since، finding the appropriate technical method requires the recognition of the river behavior and effective geometric and hydraulic factors on the erosion and sedimentation process، therefore in the present research، topographic maps and satellite images have been used for reviewing and studying the temporal variations of Kashkan river plan. For this purpose، through performing a field survey and comparison of the new and old plan of the river by GIS software، the variation of river was investigated during a 52 years period and critical periods waere identified. Also the meander characteristics of the river and development rate of meandering in the current status in 49 of river bends at the reach of 108 km، between Varpo; and Teymorabad were investigated. The results showed that 6% of bends are undeveloped، 51% are developed and 43% are more developed. Finally، with respect to the geometrical characteristics of the river and using empirical relationships، the rate of bank erosion at critical reach in the future was anticipated. The prediction results show that at، Upper Kalho and Chrkhstan، river will move 657 m. Also at Khatere، Doab، Dovale Bozorg and at upstream of Chame Pelk، its movement will be 1035m and 1297 m respectively to stabilize it naturally.