Estimation of Manning's Roughness Coefficient in Existing Concrete Open Channels by Using Roughness Coefficient Plates

Abstract

Some devices such as laser displacement sensors and digital still cameras have been used for measuring Manning's roughness coefficient in concrete open channels. Owing to their high accuracy in estimating roughness coefficients, these devices require skills and vast experience. Moreover, they cannot be used for channel surfaces under submergence conditions. Therefore, in this study, we propose a new method that uses manufactured plates to estimate Manning's roughness coefficient and examine the effectiveness of the method. The roughness of the plates is characterized by the different aggregate exposure conditions on the surface. We chose four plates, with variable exposure conditions, and applied them in the estimation of Manning's roughness coefficient in the existing concrete open channel used for irrigation. The results showed that the difference between the coefficients estimated by the plates and the laser distance meter was 0.001. Therefore, we conclude that the developed plates allow to estimate Manning's roughness coefficient without great effort even when the concrete surface is under water.