Hazard assessment and formation mechanism of debris flow outbursts in a small watershed of the Linxia Basin

The Linxia Basin is located in the transition zone between Qinghai–Tibet Plateau and Loess China. Collapse–landslide–debris flow geological disasters are particularly prevalent this region. Taking a debris that occurred Zhangjiayuan gully, Dongxiang County, as an example, characteristics formation mechanism were studied through field investigation remote sensing interpretation methods. hazard zoning influence range of analysed under different precipitation conditions using numerical simulations. results show gully experienced medium-to small-scale, rapid catastrophic viscous mud flows, with activity frequencies ranging from medium to low. Because large numbers landslides, collapses overland flows developed on bank slope, material sources for abundant but supplied intermittently. Induced by heavy rainfall, landslides slipped into then landslide mass blocked channel formed weir dam. As water converged dam body softened mud, seepage deformation occurred, burst form flow. This disaster mode represents kind rainfall-type landslide–blockage–debris chain. Under varying which rainfall occurs once every 10 years or 50 years, may break out Zheda highway associated tunnels below medium–high danger zones. When rushes mouth cannot be discharged time, it accumulates buries tunnels. Therefore, attention should given preventing such small-scale sudden strengthening early warning capacity prevention ensure safe operation highway.