Study On Assessment Of Sensitivity Of Soil And Water Loss In Changting County Based On 3S Technology

Soil and Water Loss(SWL),fundamentally caused by human's irrationally exploiting land resources,is an important factor to restrict the economic and social development of ChangtingCounty.In terms of SWL,the situation of Changting is representative in Fujian Province,even in the whole Southern Red Soil Zone(SRAZ).With the support of 3S technology,this thesis took Changting as the study area and completed the empirical study on assessment and regionalization of sensitivity of SWL by coordinating spatial and statistical analysis as well as qualitative and quantitative analysis,on the basis of presently related data and previous relevant research achievements,and theoretically underlain by the Revised Universal Soil Loss Equation(RUSLE).This is beneficial to the decision-making and practice of soil and water conservation in local along with similar areas in SRAZ,the significance of which is important.The main contents and achievements of this thesis are as follows:(1)Proposing a Simple Algorithm of Monthly Rainfall Erosivity(R)Factor(SAMREF)suitable for Changting County.It designed and implemented a localized SAMREF for Changting by using multiple regression analysis,which took the monthly R calculated by means of classic method and the monthly statistic of erosive daily precipitation as the dependent and the independent variables respectively.It turns out that the accuracy of the proposed method is significantly better than that of similar research for the same region,and it can be applied for the quantitatively estimating local SWL,as well as optimizing measures on conservation of water and soil.(2)Implementing the information extraction of all factors for sensitivity evaluation of SWL in Changting.Thereinto,the information of Rainfall Erosivity Factor was obtained by interpolating with the kriging method according to the average R(from 2005 to 2013)of rainfall observation stations in Changting and its surrounding which had been computed by the SAMREF proposed in this thesis;the information of Vegetation Coverage Factor(C)was extracted through the weighted summation operation which had been based on the Cs of multiple temporal remote sensing images calculated by the proposed localized model;and the information extraction of Soil Erodibility Factor was derived by referring to previous similar study achievements,so was the information extraction of Slope Gradient and Slope Length Factor.(3)Completing the sensitivity assessment of SWL in Changting County.In accordance to the localized information of all the factors for sensitivity evaluation of SWL,it established a criterion of sensitivity evaluation of water and soil loss for the study area by referring to the relevant research achievements and the breakpoint from classification of each factor through applying the natural break method,and implemented soil-and-water-loss single factor evaluation and comprehensive evaluation based on the criterion.Evaluation results showed that,there were four different sensitivity levels of SWL in the study area,namely,insensitive,slight sensitive,moderate sensitive and highly sensitive.Among them,the area of slight sensitivity(accounting for 59.25%of the total area of the county)was the largest,followed by that of moderate sensitivity(accounted for 38.75%of the total area of the county).(4)Analyzing the relationship between the sensitivity and the status of SWL.The status layer of SWL was calculated based on RUSLE model,and had been verified through field sampling investigation.After overlaying and comparing the layer resulting from water-and-soil-loss sensitivity evaluation and that from computation of RUSLE model,it could be found that there existed such a relationship between their spatial patterns and trends:the sensitivity level of SWL was accordingly high where SWL was serious;and the SWL usually didn't occur seriously in places where the sensitivity level of SWL was low,however,there is not always serious SWL,even no such problem in high sensitive places.(5)Setting up regionalization of soil-and-water-loss sensitivity in Changting County.In the light of the general rule of regionalization and the actual situation of Changting County,the hierarchical cluster method with constraint of spatial neighborhood relationship was applied to complete the regionalization which included two levels.Terrain features and characteristics of SWL were taken as controlling factors at the first level,and SWL sensitivity features as controlling factors at the second level.On the basis of clustering results,the whole County was divided into four regions and ten sub-regions.Thereinto,the four regions were named in a way of "location + topographic feature + degree of SWL",namely,east and north Ting,low mountain and high hill,and slight SWL zone,northwest Ting,high hill,and moderate erosion zone,central Ting,low hill,and severe erosion zone,south Ting,high hill,and slight erosion zone.