Coupling check dams with large wood retention structures in clean water

Abstract

The performance of a rake for large wood retention has been analysed in clean water and for the case of a slit check dam. An experimental investigation was conducted in a steep rectangular flume, by employing regular cylinders at different rates and rake geometry. The effects of the inclination and distance of the rake from the check dam have been analysed in terms of the trapping efficiency and backwater effect. By intercepting the incoming wood material, the rake avoids the direct occlusion of the slit check dam, preventing large backwater rises and allowing the dam to work properly even in the presence of intense woody flow. The trapping efficiency slightly increases with the inclination of the rake when it remains very close to the check dam, but it tends to decrease when the structure is out of the calm water region upstream of the dam. Additionally, a comparison between the rake performance and the check dam without retaining devices is presented.