A REVIEW: THE STUDY OF SOIL EROSION ON LOESS PLATEAU
Chen YongZong(Institute of Geography. Chinese Academy of Sciences and State Planning Commission of The People's Republic of China)
This paper briefly describes the history of researches, the achievements and the Problems in the field of soil erosion on the Loess Plateau.Before 1949, study of soil erosion on the Plateau began. It is only after 1950 that great progress has been made and achievements gained as fellows.1. Compilation of the maps of soil erosion division and presenation of a scientifically and systematicly classified erosive pattern.2 Estimatation of the delivery ratio of sediments on Loess plateau about 1.91% of 1.6×108 tons sediments transported to the lower reaches of the Yellow River from the Loess plateau, and 74% of the total sediments from the area of about 1.14×105km2, including North Shaanxi, East Gansu and West Shanxi, Furthermore, the sediments with the diameters larger than 0.05mm on the bed of the lower reaches of the Yellow River are also transpoted from the regions .59-93% of the amount of sediments in the small basins are provided by gully banks.3. The rainfall causing soil erosion is the stormrain with a period of 1 to 4 hours, medium precitation (20 to 50mm) and high intensity ( 5 to 20mm/h.) . The erosion is commonly produced 15 to 20 minutes after the surface flow appaers,snd it is exponentially related to slopes, but it will reduce as slope over 25° to 28° .The soil crust may make the runoff and erosion 5-10 times higher than that in the case without the crust4. The special geological and geomorphological conditions of the Loess Plateau staimulale natural erosion in this area.The Loess Plateau in the early period of development was covered by fairly with vegetations. Modern strong soil erosion is resulted from the natural factors and human destroy .Since the founding of new China, large-scale soil and water conservation work has been carried out, so the soil erosion in some areas has been con trolled .But in other places, erosion is increased for various factors.The basic problems in the study of soil erosion on the Loess Plateau are:1. The wind erosion and mass movement have not been quantitatively studied yet .Mechanics of splushwash and rainwash is still unclear.2. Management of scientific research is confused .Some research work is repeatly cycled at the low level.3. Research technique is not advanced, and the observation data are lack of systematization.