Contribution of Wash and Channel Sediment Sources in Supplying Storm Suspended Sediment Load in the Galazchai Watershed

Suspended sediment generation is a predominant process in most watersheds, which has an important role in total sediment yield reached the main outlet of the watershed. However, the determination of contribution of main sediment sources in the watersheds, as one of fundamental bases of sediment management practices, has been rarely considered. Hence, on the present case study was conducted Galazchai Watershed in West-Azarbaijan Province, Iran, with an area of some 103 km2 to investigate the contribution of wash and bed sediment sources in total suspended sediment yield. Towards this attempt, sediment samples from 12 storm events which occurred during the spring of 2014 and autumn of 2014, were collected and subjected to laser particle size distribution measurement. The suspended sediment particle size distribution results verified a significant contribution of wash load with an average of 89.45± 11.95% in suspended sediment supply for the study storms. The mean contribution in the spring of 2014, summer of 2014 and autumn of 2014 were founded to be 92.17, 90.71 and 85.80%, respectively. The results consequently verified the necessity of special attention to management of watershed upstream in order to plan a proper sediment management of the study watershed.