Implementation of a Flexible Wire Net Dam for Controlling Debris Flow in a Small Mountain Torrent

Debris flow is recognized as a major natural hazard in torrent landscape over the world. Various types of control structures have been employed to capture debris flow in mountain torrents of Korea. In this study, flexible wire net dam was newly designed and implemented to retain debris flow on a small, steep mountain torrent. The dam consists of a flexible net panel, wire anchors and supporting rods to dissipate the energy of debris flow. A 500 mm × 500 mm wire panel was designed to endure the impacts of debris sediments, regarding the characteristics of streambed materials on upstream torrents. The plane stresses induced by debris impacts were uniformly distributed over the panel and subjected to the wire anchors installed in river banks. The anchors were specially designed to absorb the kinetic energy of sediment movement. Supporting rods were anchored into streambed and keep the wire panel against the sediment-induced force. Designed dam was implemented in average slope of 35° torrent of Mt. Gwanak in Seoul, Korea. The dam has a 15 m bottom width and 3 m height. Design load was estimated from the size and density of stony debris materials placed in upstream torrents. A 95-percentile diameter of sediment materials (D95) was 0.5 m in size. Maximum force acting on wire net was estimated to be 14.81 kN/m for design purpose. The flexible wire net dam has well-designed and installed in a site for preventing debris flow movement. The dam can be constructed without disturbing the stream environment and with ease, so it has environmental benefit and safety performance by reducing dangerous works for construction.