ارزیابی پیوستگی رسوبی و شناسایی عوامل­کنترل­کننده ریزشوند­گی درطول رودخانه درپرچین- شرق اسفراین

Analysis of grain size parameters along the Darparchin River, with gravely bed, indicated ۳ sedimentary links that are separated from each other by ۲ discontinuities. The first discontinuity happens about ۶ km toward downstream site from sample one. This is probably related to sudden changes in slope gradient as well as distributaries entrance. These two factors are the main reasons for changes in texture of bed load sediments within the channel as well as the break in sedimentary links. Toward downstream, due to the connection of another distributary to the major river in the vicinity of Darparchin Village, the texture of sediments within the main channel change and the ۳rd sedimentary link appeared. The changes in the trend of grain size parameters along ۳ sedimentary links can be related to stream velocity and competence. These are also related to bed slope changes, which are causing selective transport as well as hydraulic sorting in sediments. These are the factors control the downstream fining trend in the Darparchin River.