Spatial Variation of Bedload Shape Characteristic towards Downstream (Case Study: Ghalesar Watershed, Sari)

Investigating downstream changes in bed load shape can be useful to detect watershed hydrological processes and it is very important to design hydraulic structures and to manage capacity of large storage dams، properly. Regarding to doing of enforcement studies، this research was conducted in Qalesar River in upstream of Chahardangeh watershed in Mazandaran Province. After recognition of the study area، 6 sections were selected towards downstream for bed load sampling. Laboratory analysis were done to measure and calculate some bed load shape characteristics including skewness، kurtosis، mean، mode، percent of sand، fine gravel، silt and clay، sediment texture، small، medium and large diameters، nominal diameter، sphericity، rounding، width ratio، shape factor and D10، D50 and D90. Results indicated a decreasing trend in shape factor and sphericity، an increasing trend in mean diameters and roundness، a complex trend in width ratio and a uniform trend in 3 axes. Our finding also indicated that this variations may be affected by physiographic، lithologic and geotechnical characteristics of the study area.