Determination of Hydraulic Roughness Coefficients of Some Vegetated Species in Awka, Nigeria

Abstract

In this study, selected types of grasses were studied to determine their hydraulic roughness coefficient and to select the most suitable grass for erosion control. The experiments were performed in twelve trapezoidal open channels measuring 5 m x 0.12 m x 0.03 m at different flow depths (0.001m, 0.002m, 0.003m, 0.004m and 0.005m) and at varying bed slope (0.2%, 0.3%, and 0.4%). Overall, Bahama grass showed the highest Manning’s n-value due to its deep root system and creeping nature. For each slope, the degree of submergence, Reynolds number, and flow depth increases as Manning’s n decreases. As the flow depth increases, the Reynolds number increased while the drag coefficient, Cd decreases.

Keywords

• hydraulic roughness coefficient (n)
• erosion
• discharge
• channel
• vegetation