Evaluation Effect of Density and Flaxibility of Non-Submerged Vegetation on River Banks and Floodplains on the Friction Factors

Friction coefficients of river banks and floodplains are influenced by two major factors which are the flow conditions and the characteristics of vegetation. The most important parameters of vegetation characteristics are its density and flexibility. Many research focused on the effects of vegetation on the friction factors of rivers and floodplains. Less attention has however been given to the effect of vegetation density. This research was performed using laboratory flume and three kinds of Non-Submerged vegetation, to evaluate the effect of the density and the flexibility of vegetation on friction coefficients. The effect of these parameters on friction factors was investigated in four density conditions. This research revealed a linear relationship between the friction coefficients and the vegetation density. For same flow conditions; same velocity and same depth of flow (submerge ratio), the amount of friction coefficient for the less dense vegetation was seven to ten percent less than that of the dense condition. Also in same flow and vegetation conditions, different friction factors were obtained because of the difference between flexibility of vegetation.