Overflow characteristics on grassed inner slope due to levee overtopping

Abstract

In this study, laboratory experiments were carried out to investigate the effect of grass conditions on overflow characteristics. A rectangular channel used for experiments is 20 m long, 2.5 m deep and 5 m wide. The levee was built in the channel. The height and crest width of the levee were fixed at 1.5 m and 1.0 m, respectively. The length of levee was 5 m. The outer and inner slopes were fixed at 1V: 2H. Two kinds of grass were selected as surface cover of the inner slope. The grass is man-made and 5.0 cm high. Overflow discharge was changed from 0.1m3/s to 0.5m3/s with a difference of 0.1 m3/s. The overflow depth and velocity along the levee slope were measured and compared with each other including a case without grass. The experimental results showed that the maximum velocity occurred at the toe of inner slope and the hydraulic loading became weaken in condition of the grassed surface compared with no-grassed surface.