QUANTITATIVE STUDY OF THE STAGE AFGEOMORPHOLOGICAL EVOLUTION
地貌发育阶段的定量研究

This paper puts forward the integral value of erosion of threshold as a quantitative standard to divide the stages of geomorphological evolution which inherits and develops the classical theories in geomorphology. The advantages by using the integral value of erosion are as follows: (1) putting the stage of geomorphological evolution into the concept of open system; (2) avoiding the uncertainty 'Caused by Strahler's Area-Altitude analysis to divide the stages of geomorphological evolution; (3.) setting up the quantitative relation between the stages of geomorphological evolution and matter movement of drainage basins; and (4) distinguishing the natural and accelerating erosion of drainage basin. By analyzising and calculating the drainage basins which belong to rolling gully area on Loess Plateau, the conclusions are reached that the drainage basin enters maturity from youth, when the integral value of erosion equals 0.30, in which the evolutionary time was 70 thousand years ago and erosional modulus was 7008 t/km'. a; the drainage basin will enter old age from maturity when the integral value of erosion equals 0.70, in which the evolutionary time will be 72 thousand years later from now on and erosional modulus will be 7008 t/km2. a only for natural process. The percentage of accelerating erosion in rolling gully area on Loess Plateau is 30% now.