The Investigation of Erosion/Accretion Pattern Change the Bashar River Based on Remote Sensing, Air Photo Images and Field Surveys

River bank erosion is one of the major sources of sediment for many rivers around the world. The aim of this study was to identify erodible riches in Bashar river because the role of this river's in development of Kohgiluyeh and Boyerahmad province. In this study, using Satellite imagery, aerial photos and field survey from 1975 to 2015, the riverbank migration patterns for period of 40 years were investigated. After creating database of recorded data Bashar river, bank lines in different years digitized. Then, by comparing successive changes in bank line position, patterns of erosion and accretion was determined. Due to dischargr and Geological factores effectes on river pattern, these factors were evaluated. The Result of for identify erodible riches in Bashar river using GPS and field surveys, verified. The area of bank erosion and accretion by comparing sequential changes in banklines position determined. For short-term analysis, the migration rate from one any image to the next image is estimated. For long-term analysis, the migration rates are based on the difference between the 1975 image as the reference, and subsequent images. The results indicate that the erosion– accretion patterns in the sub aerial and subaqueous areas of the beshar river have changed significantly since 1994. For the short-term analysis, the highest erosion and accretion amounts are 4.7 and 7 ha from 1975-1984 and 1984-1990, respectively. the lowest erosion and accretion amounts are 2.6 and 2.3 ha from 2008-2011, respectively. The highest rate of bank erosion in different reaches equal to 9.6 and 4.6 ha/y in reachs of fifth and second bserverd. Also rate of bank accretion in fifth and second reachs equal to 9.6 and 4.6 ha/y observerd. the lowest erosion and accretion rate in reach of seven equaled 11.7 and 6.4 ha/y accounted, respectively. The correlation coefficient the between erosion and discharge and annual discharge averagelly for the short-term analysis observed 0.54 and 0.44, respectively.