Study On Cause And Prevention Technology Of Mountain Torrent Disaster In Small Watershed

With small area,weak storage capacity and steep bed gradient,there are some features ofthe mountain torrents in small watershed which are shorter duration,bigger rises and higherflood peak,and the features of mountain torrent disasters are burstiness,short forecastperiod,large water yield and great destructive power,etc.The mountain torrent disasters havebecome one of the weak link of flood control and disaster reduction in China.Due to thecomplicacy,many influence factors and the scarcity of sources, the study of mountain torrentdisasters is urgently in need of the related technical support. Therefore,the study on cause andprevention technology of mountain torrent disaster in small watershed is of veryimportance.The study object of this paper is Yaoan watershed,which is in Lianzhou,QingyuanCity,Guangdong Province.The main contents of this paper are as follows:(1) The causes of mountain torrent disasters in small watershed were analyzed.Someaspects such as precipitation, gravitational potential energy,solid matter and so on wereanalyzed,and the results indicate that precipitation is an direct and dynamic factor in theformation process of the mountain torrent disasders,the adverse condition of gravitationalpotential energy is also an important factor,ande the loose solid matter in the earth’s surfacealso maks a contribution to the formation process.(2) The mountain flood risk assessment techniques were studed.There were six indexesin the flood risk assessment,which were precipitation,elevation,gradient,soil type,populationdensity and land-use type.The flood risk assessment model was built based on GIS andAHP.The regional maps of mountain flood hazard,vulnerability and risk are given,and theflood risk assessment results can reflect the actual situation(3) The methods for calculating critical rainfall were explored.Statistical and inductivemethod of region and inverse-water level method were used to obtain the values of criticalrainfall for1h,3h,6h,12h and24h.Moreover,on the basis of the relationship between intradayrainfall and effective rainfall before mountain torrent disasters, the base lines of warningrainfall and transfer rainfall were proposed to provide a reference for prevention of mountaintorrent disasters.(4) The Early-warning and Forecast System of Small Watershed Mountain torrentdisaster was built on the basis of the study of flood forecasting in the area without data. TheEarly-warning and Forecast System mainly includes critical rainfall forecasting and flood process forecasting,and Xinanjiang model and subjective forecasting were used to simulateand forecast the flood process.To the no-data area,the schemes of Xinanjiang model andGuangdong Province synthetic unit hydrograph were compared to confirm and test theparameters of Xinanjiang model.The solution can solve the problem of accuracy of floodforecast in the no-data area.(5) The engineering measures to prevent the mountain torrent disasters were put forward.The engineering measures in Yaoan watershed mainly include structural measures of floodcontrol,river regulation,works of soil and water conservation and biologicalengineering,etc.The main governing area is Changheshui River and Yaoan County,and the partgoverning area is Xiaogunshui River and Daitianshui River. The engineering measures playimportant roles in enhancing disaster prevention and mitigation capacity and protecting life inthe mountain areas.