The Characteristics And Prevention Measures Of Shitou Gully In Jiulong Country Sichuan Province

Debris flow is a geo-hazard which outbreaks abruptly and causes a severe consequence. Along with development of human society, the debris flow disasters become more severe because of peope's over obtainment of natural resource and constante destruction of the environment. Thus, in order to diminish the occurrence probability of disasters and weaken the loss of it, the investigation and assessment should be strengthen and prevention meansures should be taken.The study area of the Shitou gully is situated in the southwestern part of Jiulong country, Sichuan Province. The disaster occurred on 24^th May in 2007 and caused a directly economic loss of three million Yuan. In this thesis, we investagte the geological and geomorphologic settings and formation conditions of the debris flow by field investigation, study on the properties and dynamic characters of the debris flow, then propose the prevention measures. Firstly, analyze the various factors of Shitou Galley by studying the drainage background and its characteristics, divide the drainage area into four zones: the watering zone, the forming zone, the flowing zone and the deposition zone according to its loose material origin and terrain. Secondly, calculate the density, velocity, discharge and impulsive force of the debris flow, the result is that: Shitou gully is a very typical turbulent, site-specific debris flow at a low frequency. The dencity of the debris flow occurring on 24 May, 2007 is 1.65g/cm³, its frequency is about 50years once, its peak discharge is 143.42m³ /s, the whole impulsive force is 93.05kP, the peak individual rock impulsive force is 48.79×10⁴N. All the parameters show that the destructive power of the debris flow is very large, the people and buildings on the alluvial fan are seriously threatened. It's necessary to take prevention meansures.Based on the formation conditions, dynamic characteristics, debris flow scale at different frequency and the damaged objects, aiming at the type of turbulent and low frequency debris flow such as Shitou gully, considering preventive measures, civil control measures and farmland measures, this thesis propose a mode of township debris flow control in accordence with the principle of "comprehensive analysis, rational classification, safety and economic". A further study on civil control measures was taken: construct a gravity dam in Niuchangxiao Gully; construct a railing dam and a gravity dam in Shitou gully to barrier the debris flow and regulate its scale; build a drainage channel from the top of the alluvial fan to the Jiulong River to excretion the debris flow; construct check dams and phreatic dams to improve the stability of gully bed, reduce erosion and control the debris flow, therefore the people and structures on the alluvial fan can be protected.