Study on river plan form change in responses to change sand bars in Gamasiab River

Sand bars are river are morphology units that associated with amount of discharge change the river plan forms. The propose of this study was to investigation on changes of channel plan forms, bars and point bars in1955 to 2010 in Gamasiab River in Kermanshah province. This study used historical method and aerial photography taken in 1955, 1969, 2003 and IRS satellite imagery of 2010 with a resolution of 2 m done, Aerial photographs were orthophoto in ARCMAP software based on1/25000 topographic map. Shoreline and bars was digit and river divided 12 reach. Area of bars and point bar was measured in each reach and changes of river plan forms using of braided index and sinuosity in plan forms have been identified. Result showed that mid cannel bars area was 84.39 (ha) in 1955 increased to 204.5(ha) in 2010. This increase was changed mid bars in channel plan form from meandering to wandering gravel bed, anabranching and changes to braided. But river in downstream Reach hadn’t plan form changes and from 1955 to 2010 had a meandering plan form. Decrease in discharge, remove sand and gravel and low slope causes river hasn’t change in plan form. The total amounts of point bars area have been decrease from 849/5 (h) in1955 to 500(h) in 2010.river changes in plan form and progressive farmland cause point bar area decrease.