Journal of Food, Agriculture and Environment

Loess plateau rainfalls characteristics and influences on soil erosion

Author(s):

Li Gong*, Chunling Jin, Wen Sun, Huazhong Yang, Junhong Wang

Recieved Date: 2013-07-10, Accepted Date: 2013-10-12

Abstract:

Loess plateau is a drought and water shortage area in China. Meanwhile, the water and soil erosion was most serious in this area. Thus, it is necessary to research the rainfall splash erosion on the loess plateau. This study is of crucial importance in water and soil conservation comprehensive treatment. On the basis of intensive researches, this study considers that rainfall intensity, raindrop speed and the impact angle of raindrop with slope greatly affect the soil erosion. Particylarly, the erosion intensity is one of the key indicators that measure the amount of soil erosion. The shortcoming of most current researches was erosion calculation usually ignored the impact angle of raindrop with slope on the effect of wind. After analysing the raindrop erosion intensity indexes, this study added the parameter of impact angle of raindrop with slope in the erosion calculation equation. Based on the theorem of momentum, this study proposed the rainfall erosivity expression. Then it derived the rainfall erosivity expression in accordance with loess plateau. The expression denotes the relationship between the rainfall intensity and erosivity. During the rainfall in loess plateau region, the magnitude and direction of the wind affect the splash erosion angle between raindrop and ground. That is, the values of cos( θ + γ) greatly affects the erosivity. Finally, this study takes a certain loess plateau in Lanzhou in Gansu province of China for instance. There were 6 different vegetation regions in this area. They were barren slope region, bare slope region, alfalfa region, seabuckthorn region, caragana korshinskii region and Chinese pine region. In the 5 years observation, the results are as followings. (1) The loess plateau region rainfalls have obvious monsoon rain characteristics. The sloping field soil erosion time distribution is concentrated. The rainfall amount in July and August and the erosive rainfall amount are 52.7% and 69.1% of it from May to September. The erosion amount in July and August is 77.4% of the annual erosion. (2) In the loess plateau region, the rainfall intensity and raindrop kinetic energy have the most significant impact on the splash erosion. The rainstorms usually have high energy. So the erosivity of loess plateau rainstorm on the soil is much higher than the ordinary rainfall. (3) Rainfall erosivity is the potential hazard to the erosion of water and soil. After all, it is the early time of water and soil erosion. The erosion of rainfall to soil can be reduced by adopting scientific method, engineering measures and vegetation measures.

Keywords:

Loess plateau, raindrop, erosion, soil erosion, raindrop falling velocity, splash erosion angle, raindrop kinetic energy, rainfall intensity, raindrop terminal fall velocity, soil particles

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Journal: Journal of Food, Agriculture and Environment
Year: 2013
Volume: 11
Issue: 3&4
Category: Environment
Pages: 2502-2505

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