Discussion on soil erosion and prevention measures of soil and water conservation engineering?

Natural factors are the potential conditions for the occurrence and development of soil erosion, while human activities are the leading factors for the occurrence, development and maintenance of soil erosion. Soil and water conservation project is a measure to prevent soil erosion in mountainous and hilly areas, protect, improve and rationally utilize soil and water resources, give play to economic, social and ecological benefits, and establish a good ecological environment. The object of control is soil erosion on slopes and ditches, that is, engineering prevention measures applied under the action of various external forces and erosion forms such as water power, gravity, wind power and glaciers.

1 soil erosion factors

It can be divided into natural factors and human factors. Natural factors are the potential conditions for the occurrence and development of soil erosion, while human activities are the leading factors for the occurrence, development and maintenance of soil erosion.

1. 1 natural factors

Natural factors affecting soil erosion mainly include climate, topography, geology, soil and vegetation. Various natural factors restrict and influence each other.

1. 1. 1 Climatic conditions Climate factors have a direct impact on soil erosion, such as rainfall or snowmelt, which forms surface runoff and causes soil erosion. The other is indirect influence, such as the influence of temperature, humidity and sunshine on rock weathering and soil properties, which indirectly affects the occurrence and development of soil erosion.

Soil erosion is closely related to precipitation, and rainstorm is the main climatic factor causing serious soil erosion. Generally speaking, the intensity of rainstorm is large, and the amount of soil erosion is also large. In addition, wind, thawing and freezing are closely related to soil erosion.

1. 1.2 topography is a general form of earth surface fluctuation, also known as landform. Soil erosion mostly occurs on slopes. Therefore, topography is an important factor affecting soil erosion, and ground slope, slope length, slope shape, slope direction and ground height can all have different degrees of influence.

1. 1.3 Geological and soil conditions Whether there is soil erosion on the ground, the degree of soil erosion is closely related to geological conditions. The hardness of rocks, the nature and types of soil and the ability to resist erosion all have important influences. Especially the permeability of soil, directly affects the degree of soil erosion. Generally, sandy soil has strong water permeability and is not easy to produce runoff. However, cohesive soil has poor water permeability, and it is easy to produce surface runoff and soil erosion after rainfall, while sandy soil is easy to be taken away by rain and will also cause loss.

1. 1.4 Vegetation conditions Vegetation is the main factor to keep the soil from being eroded. Vegetation can cover the ground, intercept rainwater, reduce raindrop splash, alleviate surface runoff, and maintain and improve soil. Therefore, vegetation status is directly related to soil erosion.

1.2 Human factors

Since the appearance of human beings, they have engaged in production and life with their own activities, exerting influence on nature, among which the unreasonable utilization of water and soil resources and vegetation resources by human beings is the fundamental reason for accelerating erosion.

1.2. 1 Destroy forests, such as deforestation, land reclamation, forest fires, etc. , causing extensive damage to forests, losing the ability to store water and conserve soil, and accelerating soil erosion.

1.2.2 Land reclamation on steep slopes not only destroys the ground vegetation, but also loosens the soil and creates erosion conditions. In case of rainstorm, it will be seriously washed away, which is very harmful.

1.2.3 Irrational farming methods ridged cultivated land along the slope and artificially formed some small ditches. After the rain and snow melt, water flows down the ditch, causing soil erosion.

1.2.4 Overgrazing destroys vegetation and cannot be restored. In case of wind and rain, it will cause soil erosion and sandstorm hazards.

1.2.5 Destruction in industry, transportation and capital construction, such as mining, building factories, building roads, digging canals, repairing reservoirs, etc., has caused a large number of abandoned soil and mud to rush into rivers at will, resulting in soil erosion.

The forms of soil erosion are as follows

2. 1 surface erosion

Surface erosion is the most common form of soil erosion, which means that scattered surface runoff washes away surface soil particles from the ground. Most of them occur on sloping farmland or barren slopes without vegetation or reliable soil and water conservation measures.

2.2 Gully erosion concentrated water not only scours and destroys the soil, but also gradually forms gullies that cut into the ground, which are connected by small streams to form streams. With the increase of momentum, gullies also deepen and widen, and over time, large gullies are formed.

2.3 The stability of the soil on the steep slope eroded by gravity is maintained by the friction resistance in the soil and the fixation of natural vegetation. When some external force or vegetation is destroyed, soil friction decreases, which will cause soil collapse, such as falling rocks, landslides, mudslides and so on. Because it is formed by gravity, it is generally called gravity erosion.

3 soil and water conservation engineering measures

Taking small watershed as a unit, adjust measures to local conditions, fortify and prevent disasters, and simultaneously ditch and slope. After the completion of the project, the effect is quick, and the initial benefit of water storage and sediment retention is remarkable, which is as important as agricultural farming technical measures and plant measures. Various measures are responsible for the prevention and control of various parts of mountains, slopes, ditches and Sichuan beaches, and can only cooperate with each other, but cannot replace each other.

Soil and water conservation engineering measures are to build soil and water conservation projects on hillsides, gullies and rivers with soil erosion, to stop floods and sand, to achieve the purpose of preventing soil erosion, to change the natural ecological environment of small topography, and to provide excellent water, fertilizer, heat and gas conditions for new ecology.

According to the different prevention and control tasks, soil and water conservation engineering measures can be divided into the following four types: slope control engineering; Waterway regulation project; Flash flood drainage project; Small water storage project.

3. 1 Slope treatment project

The first project to control soil erosion, local artificial change of small topography, local interception and infiltration of rainwater and snowmelt water, reduce or prevent the formation of surface runoff, and prevent soil erosion on sloping land. Measures belonging to hillside protection engineering include terraces, retaining ditches, horizontal ditches, horizontal steps, water dustpan, fish scale pit, hillside intercepting ditch, water kiln (dry well), reservoir, retaining wall, etc. to stabilize the lower part of hillside.

The role of terraced fields is to reduce runoff speed, cut off runoff streamline and prevent soil erosion. According to the cross-sectional form of terrace, it can be divided into horizontal terrace, inclined terrace and sloping terrace. Horizontal terraces have the best effect.

Henggou is commonly known as Zhugou. The purpose of this measure is to make the surface runoff more evenly stored on the slope.

The function of slope intercepting ditch (around mountain ditch, intercepting ditch) is to guide slope runoff to water storage project or discharge it down the slope into the valley to maintain soil and water.

Fish scale pit is not only an engineering measure for soil and water conservation, but also a good method for afforestation and soil preparation. The upper part is linear, and the lower part is cultivated into a ridge, which is half-moon or oval, and is arranged on the slope in the shape of a pin, or it can be combined with a horizontal ditch.

Reservoir, also known as waterlogging pool, is a water storage measure created by people in arid areas, just like water cellar. Its main function is to store rainwater leakage in mountain streams, intercept mountain torrents, relieve water potential and prevent soil erosion. This measure is rarely used. It needs to be used in areas with thick soil layers, and more soil is used.

3.2 Waterway Regulation Project

The last line of defense to control soil erosion areas. The function is to prevent the gully head from advancing, cutting the gully bed and expanding the gully bank, slow down the longitudinal slope of the gully bed, adjust the peak flow of mountain torrents, reduce the solid content of mountain torrents or mudslides, and make the mountain torrents safely discharged without causing disasters to the alluvial cone at the gully mouth. The measures that belong to the gully control project include: gully head protection project, ancient square project, various sand dams with the main purpose of retaining and regulating sediment, silt dams and gully revetment projects with the purpose of retaining mud and silting up land and building basic farmland.

The ditch head protection project is to build intercepting ditches around the ditch to prevent the rain from scouring the ditch. Generally speaking, there are two kinds of canal head protection works: continuous and intermittent. Continuous type is suitable for flat ground in gully region, usually there are two ditches at the head of the ditch, and the direction of the ditch is roughly parallel to the ditch side; Intermittent is suitable for steep slopes in hilly areas. The depth of furrow is 1 m, and the furrow is divided into main sections, and the interval between sections is generally1~ 2m.

The reinforcement project is one of the effective measures to prevent gully bed erosion. It can slow down the water flow, reduce the water flow speed, prevent the gully bed from scouring, and also stop mud and sand to form a platform. There are many kinds of workshops in the valley. According to building materials, it can be divided into Tugu Workshop, Shigu Workshop, Jiangshigu Workshop and Liu Zhuang Valley Workshop. According to its nature, it can be divided into two categories: permeable valley workshop and impermeable valley workshop.

3.3 Small Water Storage Project

The function of small water storage project is to intercept slope runoff and underground undercurrent, which is an important measure to develop irrigation, ensure the stability of agricultural production, and comprehensively develop and utilize hydraulic resources. It will greatly promote the economic development in mountainous areas. Small water storage projects also have significant benefits for soil and water conservation in the upper and lower reaches of small watersheds. Small-scale water storage projects include small reservoirs, water storage ponds and dams, land reclamation, land inundation and water diversion up mountains.

Small water storage projects mainly focus on water storage, and also have comprehensive benefits such as irrigation and fish farming.

When planning and arranging comprehensive management measures for small watersheds, we should follow the principle of "paying equal attention to prevention and control, adapting to local conditions, making overall plans, comprehensively managing, eliminating pests and promoting benefits", rationally utilizing land, adapting to local conditions and being practical. In practice, we should implement the principle of "centralized management, continuous management, equal emphasis on gully and slope management, and slope management as the main task". The flood design standard of soil and water conservation engineering measures is determined according to the engineering type and the importance of the protected object. The slope engineering is designed according to the 24-hour maximum rainstorm standard of 5 ~ 10a. Flood control standards for gully control projects and small water storage projects are determined according to the type and scale of the projects. Siltation dams and small reservoirs are generally designed according to the return flood of 10 ~ 20a, and checked according to the return flood of 50 ~ 10~20a. In general, the flood diversion project is designed according to the 5 ~ 10a flood return period.

Comprehensive management of small watershed is a systematic project, including many measures. With the development of systems engineering, systems engineering theory will be more widely used in the planning and design of soil and water conservation projects. In addition, in order to modernize the design and construction of soil and water conservation projects, computer-aided design methods and advanced construction machinery and equipment will be gradually popularized.

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