Influence of Lateral Water Withdrawal on Bed Form Geometry in a Channel

Abstract

In flood protection engineering, side weirs or overflow dams are used to divert water in a controlled way into flood plains as soon as the discharge capacity of the main-channel is reached. Because of the lateral loss of water, the sediment transport capacity is reduced, resulting in local sediment deposition near the side overflow. Moreover, bed form characteristics such as length, height, steepness, and stoss and lee slope angle are affected by the lateral water withdrawal. Both phenomena are responsible for an increased side overflow intensity compared with plane bed conditions. The results from a systematic flume study show that the shape of observed bed forms is highly three-dimensional and that three distinct regions along the channel axis can be identified. The first one extends from the channel entrance to the upstream weir corner, the second one comprises the reach of the weir, and the third one represents the reach downstream of the weir. The description of bed form shape by approaches from literature shows reasonable agreement with measured bed form geometry.