Effect of rigid, bank vegetation on velocity distribution and water surface profile in open channel

Abstract

The effects of rigid ditch bank vegetation on velocity distribution and water surface profile in trapezoidal open channels were investigated. Forty-eight tests were used to study the impacts of different vegetation densities. Tests were run for three vegetation densities (1,600, 400, and 178 stems/m2) along a fixed, 4.00 m reach, against four different discharges, each with three different depths. The measured water levels and velocities were analyzed and it was found that increasing the vegetation density increased the water depth upstream of the vegetated reach. while lowering it within it, when compared to the unvegetated case. The water's velocity profile as a ratio to the unvegetated case (V/u) is sigmoid, i.e., the maximum velocity (V/u) max occurs in the lower half of the water column, increasing shear stress near the bed, and, in turn, the likelihood of bed erosion along the vegetated channel's centerline. V/u increased with increasing vegetation density and Fro. A multiple regression analysis was done to assess the impact of ditch bank vegetation density on flow parameters. HIGHLIGHTS The study examines the hydraulic issues that may arise in trapezoid open channels due to the presence of vegetation on its sides slopes.; The presence of vegetation changes water levels and increases velocity near the bed which increases the possibility of bed erosion.;

Keywords

• density
• empirical equations
• rigid ditch bank vegetation
• velocity distribution
• water profile