Debris Flow Disaster Prevention Research On Yatun Gully Of Jiuzhaigou County In Sichuan Province

Debris flows are widely distributed in China. Many provinces, forexample, Sichuan, Yunnan, Tibet, Gansu and so on, suffer most seriousgeological disasters. In recent two years rainstorm frequently occurred,which brought great damage to the safety of life, property for people andsignificant achievement reconstructed after the earthquake. Therefore,debris flow research and disaster prevention and reduction are becomingmore and more important.Debris flows happened in Yatun gully ofjiuzhaigou county, The debris flows harmed to two residential place,446persons,105households. Besides, The highway from Songpan toJiuzhaiguo Nature Reserve is possibly damaged by the debris flows. Thedebris flows in Yatun Gully has directly affect the development of touristattraction.This paper system analysised based on the debris flow investigationthe circumstances and characteristics of Yatun debris flow, the material sources of forming a debris flow, the landform conditions and watersources, the movement characteristics, the debris flow scale and disastercondition. Next, the paper predicted evaluation of the possibility, risk,endanger scope and extent of harm. Lastly, The basement of parametersof debris flows were calculated, and prevention measures were give.Actual effect was verified after engineering control.The results and knowledge can be obtained by the theme:1、The debris flows in Yatun Gully is low frequent-water sand mold-heavy rain-gully debris flow, the easy-happening degree was59forquantitative scoring, with density as high as1.405t/m3, is turbulentdebris flow.2、The Yatun Gully has two important second branch ditch, one ofthem is Qingshui Gully, and the other is debris flows gully, which has theconditions of getting material sources. Yatun Gully is pyriform, and itsmorphology of ditch domain is high mountains, steep slopes. In upstream,gradient ratio is high, and gully is narrow. In downstream, gradient ratiois low, and gully is wide. So Yatun Gully is very easy for watercatchments. Heavy rain is domain factor of causing debris flows.3、The head of Yamu gully of Yatun Gully’s branch ditch-The headof the Xuxia gully-Yatun gully is wide and slow, which is easy for storingmaterial source of debris flows. There the solid material can be weakenedduring movement of debris flows downstream. The density of the debris flows is diluted, so the incompact substance can stop. The debris flowsget into the Yatun gully downstream becomes water sand mold finally.Therefore, the head of Yamu gully-the head of Xuxia gully-the upstreamof Yatun gully can be as the place for silting. Because of it, the Yatungully has never occurred large scale viscous debris flow, only turbulentdebris flow.4、The debris flows of main channel in the Yatun gully is turbulentdebris flow, water sand mold, so some measures were taken forpreventing. Direct protection and local application are taken and stableengineering is impossibly taken. The engineering already existed wasrepaired and strengthened. The wall was built in the place for havingeasily scour to prevent erosion.5、After regulation project, the heavy rain dropped in jiuzhaigoucountry in the spring of2010,2011. Yatun Gully has happened debrisflows. As this paper described, the solid material was decreased, thedensity was lower and lower while the movement of debris flows, andwater and sand was separated finally.