Oueme Bridge, hydraulic study: flooding risk and stability assessment using MIKE 21

摘要

With the objective to evaluate if rehabilitation of the road crossing the Oueme River in Benin will lead to an increased risk of failure for the Oueme Bridge due to higher extreme water levels and/or discharges at the bridge the MIKE 21 HD model was used to simulate the extreme flow conditions in the Oueme River basin before and after the planned road rehabilitation. The stability of the bridge was subsequently analysed. The main findings in the project were the following: 1) It was confirmed that large stretches of the existing road frequently are being flooded, whereas no parts of the rehabilitated road are being flooded; 2) The water level at the bridge does not increase after rehabilitation of the road; 3) The water discharge at the bridge is significantly increased for return periods above app. 1 year; and 4) The increased discharge does not affect the stability of the bridge directly but could in a longer term affect the river banks or bed and thereby indirectly the stability of the bridge.