Evaluation And Governance Programs About Low-frequency Debris Flows In The Dong Wopo Village, Jixian County

Debris flow is a kind of very common geological disaster which often happens inmountain area. It is a torrent carrying a lot of sand and stones. It is generated whentorrential rain, snow melt and other Water powers (dam break, glacier) act onthe unstable surface loose earth. It happens suddenly and has a high flow speed. Then ithas a strong destructive power.The debris flows in Dongwopu village, Jixian county, developed in Panshanmountain. It is the middle and low landform. formation area 's altitude is generally inthe400~600m, and slope is generally greater35°.The main mountain of Panshanmountain, Guayue mountain, has the highest altitude which is857.3m. Forming region'sarea is about20km2. Debris flow's accumulation area is located in the low mountains,andthe east and west parts are very high, the middle is low. The highest point is345.7mlocated in the east boundary of assessment area. The lowest point is190.8m located alongBaoping highway.The debris flows in Dongwopu village, Jixian county, developed in granitedistribution area in Panshan mountain. The granite in this area is composite intrusiverocks: they are medium to coarse grain granite intrusion, medium to fine particle biotitegranite intrusion, containing spot quartz monzonite intrusion and fine-grainedgranite intrusion. There is only dolomite distributed in debris flow accumulation area.Due to the differences between the intrusions, the strength and the resisting weatheringability of rocks are distinct. In addition, three main groups cracks with varying sizes anddifferent directions in the rock and dense bands of local joints, provide favorableconditions for weathering so that a large number of fine-grained generate. The specialgeological environment results in the distinctive landforms,that the catchment area islarge but water outlet is small. When enough rainfall intensity is accepted, owing thatinfiltration capacity of the bedrock areas is under10%,the plenty of water in formationregion can't be drained off in time, a large number of water and rickle mix and flow intocirculation area, then, generate a debris flow. According to the preliminary in-site investigation, the gully debris flow in Dongwopuvillage, Jixian county has the following characteristics: interval,oversize and lowfrequency, and it is classified as viscose debris flow. The provenance's volume of theforming region and circulation area is6.667million cubic meters by the method ofcalculating the profile. It is predicted that the speed of the debris flow is9.7m/s and thesection height beside the intersection of the two gullies is8.4m in the extreme the mostadverse conditions. The debris flow's speed is usually5.3m/s and the correspondingsection height is less than4m in general.Based on the rule of after before deciding on,putting the prevention first,combiningprevention with controlm,the management engineering needs regionalization, that is tosay,the formation area,circulation area and accumulation area are respectively controlled.The treatment methods are divides into biological control measure and mechanical controlmeasure. Moving off the small mountain liked collapse between GanLu temple andShuangfeng temple in the Channel, get through the channel from main ditch to south ditch,and combining reinforcement and biological reinforcement method to strength rock-filldam. Proceeding in the light of local conditions to plant trees to reduce water and soilerosion. Building gabion dam in circulation area to guarantee the safety in north; Buildingstop silting field in accumulation area and desilting regularly to ensure the safety ofperipheral and downstream areas.