A laboratory study of vegetation effects on preventing soil erosion in water catchments

The existence of vegetation cover in a region can reduce the velocity of surface run-offand prevent soil erosion. This can substantially control the occurrence of destructivefloods in the region. One reliable method used in protecting flood-forming catchmentsis the biological method. Also, one factor that represents the hydraulic resistance inplants is roughness coefficient. Measuring the coefficient and its impact on the flowvelocity and shear stress reduction in the plants is of outmost importance. One of theknown species used extensively in soil stabilization and protection is Tamarix sricta.This species resists against various climates and is easy to be planted. With its needleleaves and rough external organs, Tamarix sricta reduces the flow velocity and preventsfurther soil erosion. In this research roughness coefficient of the Tamarix sricta wasinvestigated. The plant studied in non-submerged and sub critical condition flow using aflume with the length of 12.6 m, width of 0.5 m and height of 0.6 m in differentvelocity, discharge and depths. The height of plants in this is 35 cm with a naturalarrangement in trays of 2.8 m in length laid over the bed of the flume. The total numberof the experiments is 22.The results of this study show that roughness coefficient ofplants is function of velocity, depth, hydraulic radius and plant types. Because of itshigh roughness, this species is an appropriate alternative to be used in reducing the flowvelocity and protecting the soil from any erosion possibility.