Factors causing soil erosion natural factors
⑴ Climate: All climatic factors will affect soil erosion, among which rainstorm is the direct driving force and the main climatic factor causing serious soil erosion. Heavy rain has large raindrops, large rainfall kinetic energy and strong splash erosion, and the runoff formed is fierce, short in duration and strong in intensity.
⑵ Topography and geology: Slope, slope length and slope type have an important influence on the occurrence of soil erosion. Rock properties affect the formation of weathered materials and soil types, as well as the corrosion resistance of weathered materials and soil. In addition, the dip angle of strata also has an effect on soil erosion.
human factor
Rapid population growth, serious environmental population overload, continuous destruction of vegetation to reclaim wasteland, excessive use of natural resources, resulting in unreasonable land use structure, excessive proportion of cultivated land (mainly sloping farmland), extensive agricultural management, low production level, overgrazing of natural grassland, serious degradation, failure to play the ecological protection benefits, resulting in increased soil erosion and deterioration of the ecological environment.
The second is the vicious circle of "accumulating more and getting poorer, accumulating less and accumulating more and getting poorer". In addition, human activities such as indiscriminate digging and logging, and the lack of attention to the protection of water and soil resources, natural vegetation and soil and water conservation facilities in production and construction projects in recent years have artificially caused new soil erosion.
The harm of soil erosion is 1, which makes the land productivity decline or even lose. The area of soil erosion in China has expanded to 6,543.8+0.5 million square kilometers, accounting for 654.38+0/6 of the whole country, and 5 billion tons of soil is lost every year. The loss of nitrogen, phosphorus and potassium fertilizer in soil is estimated to reach 40 million tons, which is equivalent to the current annual fertilizer application in China, and the economic loss is equivalent to 2.4 billion yuan.
2. Siltation of rivers, lakes and reservoirs. Although the soil erosion in Zhejiang Province is relatively light, the riverbeds of eight river systems in the province have generally increased by 0.2-0. 1 m, and the navigable mileage of inland rivers has decreased by 1000 km compared with the 1960s. . The lake area has been reduced from 39 15 square kilometers in 1954 to 2740 square kilometers in 1978. More seriously, the water level of Dongting Lake is 3 meters higher than that of the land around the lake, which has lost the flood diversion function of the Yangtze River. This is a very serious problem.
3. The polluted water quality affects the ecological balance. At present, a prominent problem in China is the serious water pollution of rivers, lakes (reservoirs). Soil erosion is an important cause of water pollution. The water quality of the Yangtze River is being polluted, which is a typical example.
How to control soil erosion (1) Biological measures: planting trees and grass according to local conditions to improve vegetation coverage;
(2) Engineering measures: terraces, earth dams, fish scale pits, etc.
(3) Agricultural production measures: returning farmland to forests and grasslands, and prohibiting land reclamation on steep slopes;
(4) Properly handle the waste residue and soil in mining, road construction and other projects to avoid the formation of new sources of soil erosion;
(5) Small watershed management, gradually changing to large-scale management.