Abstract: It is generally acknowledged that the evolution trend of loess landform is from loess tableland to loess ridge,and then to loess hilly. But in fact,the formation and evolution of loess landform is much more complex. The study quantitatively determined the development stage of watershed landscape by using the method of hypsometric integral value,information entropy and integral value of erosion,which helped to understand the basic law of landscape development. First,according to the north-south longitudinal distribution regularities of loess geomorphy in Luohe drainage basin,and referring to "The landscape types map of Chinese Loess Plateau" compiled by Zhang Zonghu in 1986,the Luohe drainage basin was divided into three landform areas from south to north in turn,that is Luochuan loess tableland,Ganquan-Zhidan loess ridge area(mainly)and Wuqi loess hill area(mainly). Second,with the spatial analysis function of GIS,the paper drew the Strahler curves for 3 different landform areas and made a quantitative calculation on the hypsometric integral value,information entropy and integral value of erosion in Luohe drainage basin by using the DEM data of the study area. Results showed as follows:(1)The values of three kinds of landform areas all belong to the quantity characteristic value range of maturity stage,indicating that the overall development status of Luohe drainage basin has begun into the maturity stage. But the developmental stages of different geomorphic partition were not the same.(2)According to the topographic features of Luohe drainage basin from north to south,erosion cutting intensity and the current situation of development,the total topographic feature of study area from north to south is from complex to simple. Therefore, in theory,from upstream to downstream,the S value of area-altitude integral curve for different landform of study area should be increased gradually,that is,S(loess hill)< S(loess ridge)< S(loess tableland). This means that the geomorphology of study area in whole would be younger the farther it went downstream. But the actual calculating result showed that the size order of S value on area-altitude integral curve of different landform area was:Wuqi loess hill area(mainly)< Luochuan loess tableland area < Ganquan-Zhidan loess ridge area(mainly), which is not consistent with theoretical situation. This paper thinks that this may be caused by the increase of erosion intensity on Luochuan loess tableland in recent years. The increase of erosion rate in modern time has a certain influence on the landscape development of Luochuan loess tableland area.

Key words: Luohe drainage basin, geomorphologic evolution, hypsometric integral value, information entropy, integral value of erosion, quantitative analysis