Natural factors.
There are mainly four aspects: climate, rainfall, ground material composition and vegetation.
① Terrain: gully developed with steep slope; The steeper the slope of the ground, the faster the surface runoff speed and the stronger the erosivity to the soil. The greater the slope, the more surface runoff collected and the stronger the scouring force.
② Rainfall. The rainfall that causes soil erosion is usually rainstorm. Only when the rainfall intensity exceeds the soil infiltration intensity will surface runoff occur, resulting in surface erosion.
(3) The composition of ground materials.
④ Vegetation. Forest and grass vegetation with a certain canopy density can protect the soil from erosion. The higher the canopy density, the stronger the soil and water conservation capacity.
Soil erosion refers to the phenomenon that due to the influence of natural or man-made factors, soil and water are lost at the same time, and rainwater cannot be absorbed locally, so it goes with the flow and washes the soil. The main reasons are steep slope, improper land use, vegetation destruction, unreasonable farming techniques, loose soil, deforestation and overgrazing.
The harm of soil erosion is mainly manifested in the following aspects: (1) the cultivated layer of soil is eroded and destroyed, which makes the soil fertility exhausted day by day; Blocking rivers, channels and reservoirs, reducing the benefits of water conservancy projects, and even leading to floods and droughts, seriously affecting industrial and agricultural production; Soil erosion poses a serious threat to agricultural production in mountainous areas and downstream rivers.
China is a mountainous country, and the mountainous area accounts for 2/3 of the land area. It is also the country with the widest loess distribution in the world. The hilly loess area is undulating.
Loess or loose weathering crust, without vegetation protection, is prone to erosion. Most areas have a monsoon climate with concentrated precipitation. The precipitation in rainy season often reaches 60% ~ 80% of the annual precipitation, and there are many heavy rains. Geological and geomorphological conditions and climatic conditions that are prone to soil erosion are the main reasons for soil erosion in China.