Study On The Risk Assessment Of Mountain Torrent Disaster From The Perspective Of Land Utilization

Created by heavy rainfall in small basin in mountainous area,the mountain torrent is defined as a kind of surface runoff featured with burstiness,sudden swelling and sharp drop.Once happened,it will cause huge casualties and property loss.Based on the characters of the mountain torrent disaster and the practical requirement,this paper not only made an analysis on the disaster factors from the perspective both of hydrology and geography,it discussed the human factors that contribute to the mountain torrent from the aspect of Land utilization.Analytic Hierarchy Process and GIS spatial analysis were adopted to build an improved evaluation system in order to carry out an quantitative assessment on the torrent disaster in a northern mountainous county of arid and semi-arid climate.Emphasis has been made as the following:(1)Analyzing the risk factors from the perspective of land utilization.As we know,the flood control and disaster reduction project all over the country could only can be implemented through the land use planning.So as for the mountain flood disaster risk evaluation in this thesis,we not only considered the hydrological and geographical index in the traditional evaluation,but also comprehensively took into account the related land use factors,including the soil type,land use pattern,roading density,population distribution,GDP per land unit and current flood control facility.In this way,the evaluation result will be more useful for the land use planning that is targeted at flood control and disaster reduction.(2)Integrating the multi-source data and improving the evaluation index system.The mountain torrent disaster risk evaluation based on land use analysis should integrate the multi-source data to build a relative perfect evaluation system.On one hand,we should redefine the rainfall based on comprehensively analyze.Considering the climate feature of the Northern arid area and the character of the torrents,rainfall data of July and August in summer season were chosen to be a new disaster-causing factor.This new factor will be decided by four index at lower lever,including the maximum 24 hour rainfall,maximum 6 hour rainfall,maximum one hour rainfall and maximum 10 minute rainfall.On the other hand,it is for the first time that the human influenced factor,the current disaster reduction factor,which concretely including the project and non-project measure aimed at flood control and disaster reduction,will be taken into consideration in the assessment system.Thus the whole evaluation system will be more integrated and scientific.Moreover,this paper made trial on improving the vulnerability index system by adding the GDP per town into the system as an economic value index.(3)Carrying out a case study of mountain torrent disaster within county region in the northern China with arid climate.The current researches of mountain torrent have been focused on the large basin in the South,and relatively the Northern torrent study is less.In fact,most of the North area in our county are of arid and semi-arid climate,the rainfall distribution were extremely uneven both in time and space.In addition,the elevation in Northern mountain is fluctuated,and the vegetation coverage rate is comparatively lower than that in the South.All of these elements lead to frequent mountain torrent disasters in this area.Taking Gulang county of Wuwei city in Gansu province as an example,this paper carried out a case study on the risk evaluation of mountain torrent disaster in the arid and semi-arid area in Northern China.This research is of significant value for the disaster control and reduction in the North.(4)Testing and verifying the evaluation result with historical data of mountain torrent disaster happened in the study area.The evaluation result was tested with the data of historical mountain torrent disaster over the recent fifty years.Then,the historical data was serve as an evaluation factor to verify the existing assessment model in order to improve the evaluation precision.The historical data,which covered long time span,is capable of effectively testing the result.As a matter of fact,the result of assessment well conformed to the distribution of mountain torrent disaster happened in the study area in history.The above method discussed in this paper can provide strong technical support to the disaster control,reduction,precaution,arrangement and land utilization after the disaster of Gulang county.