A Research On Fitting Method And Contrast In Drainage Area Threshold Based On Various Scale

So far extracting the watershed based on digital elevation model(DEM)has been a hot spot in hydrologic research,though the determination of drainage area threshold is a key point on this process.Now the methods of determination of drainage area threshold in rapid and scientific still under discussion.Therefore,the study opened up the research to eliminate the random and determine scientific nature in drainage area threshold.Meanwhile,it identify the long year average precipitation,the skand content of soil,the clay content of soil,and the index of vegetation in researching area as the elements of the influence in drainage area threshold.Moreover,we purpose a idea that could apply elements to fit the drainage area threshold though and thus to ensure threshold rapidly.The main research contents are as follows:(1)The relationship of threshold and elements is explored,and the change of various scale is compared.It is show that the relativity of threshold and slope come to enhance by the precise description on geography and the enhancement on scale of drainage,and the relationship of threshold and others slope have reduced under the same condition.(2)Both multivariate-fitting and weighted-fitting were taken to fit the threshold.And contrast its effect in two scale,contrast the result of fitting in different scale by the same fitting method further.It is show that weighted-fitting over multivariate-fitting on both the method.In addition,for a fitting in various scale,it is result that weighted-fitting shown more accurate in a large scale,though multivariate-fitting shown more accurate in a small scale.