The Study On The Difference Of Terrain Feature In Different Types Of Regions In The Loess Plateau

In this paper,used the methods of fractal,period analysis and GIS,the fractal dimension value of channel network,the gully distribution spectrum and the harmonics model,the site structure could be obtained in different types of regions in the eastern Loess Plateau.The differences of terrain feature could be analyzed.There have three aspects that include:calculate box-counting dimension and gully density in sample areas.Embody the characteristics of gully network distribution.Get the fractal dimension value of gully formation in different times by setting diffenent confluence cumulative account.Caculate gully distribution spectrum and the harmonics model by using period analysis and harmonic analysis methods.Find the differences of the main gully distribution spectrum and tributary gully spectrum in different areas.Find the difference of land site structure in different areas.Study on box-counting dimension of gully network:the fractal dimension value of gully network increased with the increase of the threshold of confluence cumulative account.All of the value lied in the interval of 1.15-1.52.When the confluence cumulative account is 100 or 500,the maximum fractal dimension value is Xifeng sample area in gansu province,the next is Jixian sample area in shanxi province,the value of Guyuan sample area and Ansai sample area is nearly the same.When the confluence cumulative account come to 1000 or 1500,the order of fractal dimension value in four sample areas is:Jixian sample area＞Ansai sample area＞Xifeng sample area＞Guyuan sample area.When the confluence cumulative account came to 2000,the order was: Guyuan sample area＞Jixian sample area＞Xifeng sample area＞Ansai sample area.The thend of fractal dimension value and gully density is almost the same.Study the spectrum of gully distribution by using harmonic method.The results showed that main channel of different regions in the Loess Plateau have different spectrums,The spectrum of the gully plateau region of Loess Plateau was greater than the transitional region and the hill and gully area of Loess Plateau.The spectrum of he transitional region was also greater than the hill and gully area of Loess Plateau.We get 10 groups of profile data which had the same distance in each studyarea,the spectrum of tributary gully in the Loess Plateau mainly lies in 400m-800m which account for 97.5%of the whole.The result from t-test of the spectrum of tributary gully showed that Xifeng,Jixian and Ansai were the same group of spectrum(P＞0.05),while the spectrum of tributary gully in Guyuan was different from Xifeng,Jixian and Ansai,the difference was significant(P＜0.01).By analyzing the average terrain slope greater than 5°in different regions,we could find that the average terrain slope of Xifeng in Gansu is more than the average terrain slope of Jixian in Shanxi and the average terrain slope of Jixian in Shanxi is more than the average terrain slope of Ansai in Shaanxi and the average terrain slope of Ansai in Shaanxi is more than the average terrain slope of Guyuan in Ningxia.We could also find that the average spectrum of tributary gully decreased continuously with the increasing of the average slope.So the average terrain slope is an important factor for the spectrum of tributary gully.Structure of site type analysis:The distribution form of land site in the hill and gully area of Loess Plateau and the transitional region in the group of slope was approximative normal curve.The peak value of the slope in different types of regions was more or less different.The peak value of Guyuan in the fifth vice-hilly and gully region is in the interval of 15-20°,and Ansai in the second vice-hilly and gully region stayed in the interval of 20-25°,the peak value of Jixian and Ansai was almost the same.The distribution curve of Gansu had two peak values,the first one was in the interval of 0-5°,which account for 44.14%of the total area,the second peak value lied in the interval of 30-35°,which account for 10.51%.By comparison the area ratio above the slope of 15 between the gully plateau region of Loess Plateau and the hill and gully area of Loess Plateau,We could find that the value of the hill and gully area of Loess Plateau was significantly greater than the gully plateau region of Loess Plateau.However,the peak value of he hill and gully area of Loess Plateau was obviously smaller than the gully plateau region of Loess Plateau.As to the aspect structure analysis,the ratio of sunny slope in Xifeng sample area was the largest,reached to 53.26%,the next was Jixian sample area,which was 52.11%,the third one was Ansai sample area,which was 50.43%,the last one was Guyuan sample area,which was 44.86%.Base on the types of land site,statistic the ratio of diffenent land site in the four sample areas,the result showed that the type of shade side gentle slope in Guyuan and Xifeng account for the most,which respectively is 29.66%and 24.76%.The area ratio of diffenent land sites in different type of regions have larger variety.