Geobag stepped spillway for check dams: A pilot study

Abstract

Check dams are widely used worldwide for the soil and water conservation. Many of them have no spillways, resulting in frequent dam breach failures during heavy rainfall events. This paper proposes a new geobag stepped spillway for small check dams. The structure of the spillway primarily consists of a stepped chute created from geobags filled with local soil compacted and consolidated with a small amount of cement. The developed composite geosynthetic material exhibits water erosion resistance, high strength against puncture, and high tensile strength. To examine the feasibility of the proposed geobag stepped spillway, a prototype pilot test was designed and constructed in a check dam in Shaanxi Province, China, with a height of 10 m and a downstream slope of 1 (vertical) to 2 (horizontal). More than 30 overflow tests were done for a geobag stepped spillway under uncontrolled and gated weir flow conditions. Based on the measurements of flow velocities and flow depths of four cross sections, it was observed that the energy dissipation ratio ranged between 73.8% and 92.8% for all the examined conditions. In addition, no significant deformation of the geobag stepped spillway was observed, although the maximum flow velocity at the spillway toe was 6.7 m/s. This study confirms that the proposed geobag stepped spillway is a promising approach for providing an effective, safe, and economical flood release structure for small check dams.