IMPACT OF TREE VEGETATION FRINGED MOUNTAIN RIVERS ON HYDRAULIC PROPERTIES UNDER LABORATORY CONDITIONHadi Ghasemi Kahrize, Seyed Habib Mousavi Jahromi, Nadergholi Ebrahimi , Hossein Sedghi, Mahmood Shafaei
Nowadays, there is an increasing attention to the river in water resources development programs. Vegetation is found to be an essential and effective element on rivers mainly reducing river hydraulic conductivity due to increased roughness and also is considered as a natural protector of river margins and banks as well as their biological stabilization. In addition to bed material, long and short vegetation covers over bottoms and sides are found to be the roughest barriers to fluid flow, which causes added roughness of fluid flow path and increased absorption of fluid power and energy. This study examined the impact of the trees fringing the mountain river on hydraulic properties and roughness coefficient using a physical model with fixed gradient of 1%, width of 1.5 m, height of 90 cm and length of 14 m and flow rates of 5 lit/se, 11 lit/se and 20 lit/se. The results suggest that change in energy gradients, flow rate and depth, particle sizes of bed load and bed material and vegetation cover in margin of waterway can create multiple roughness. This factor is not constant and increases with vegetation density and size of bed material, however it reduce with the speed and depth of flow.