Streamwise velocity distribution in irregular shaped channels having composite bed roughness

Applications of the proposed model by Maghrebi which is able to predict the isovel contours quantitatively in a section of an open or closed channel both with irregular shapes and roughness, have been presented [Maghrebi MF, Rahimpour M. A simple model for estimation of dimensionless isovel contours in open-channels. Flow Meas Instrum 2005;16(6):347–52]. In the present paper, the model is applied to a flume with a composite roughness as well as to rivers with irregular cross section geometries. The obtained isovel contours in a flume section with nine cases of composite roughnesses are used for discharge estimations. Then, they are compared with measured ones. Model predictions are well correlated with the measured data. The isovel contours obtained by applications of the model to river sections are used to estimate the depth-average and surface velocities. Then they are compared with the measured data at the corresponding sections. The predicted results of water surface velocities are in good agreement with the measured data in a cross section of the River Unon in Japan. The result of the depth-average velocity shows, even better agreement with the measured data as well as the best analytical results for the River Severn in the UK.