Erosion control in Slope

If we want to know the solution of erosion control in slope at first we have to acquire a clear knowledge about erosion and uses of slopes in structures. Erosion is a natural phenomena in which earthen materials are worn away & transported by natural forces as wind, water etc. And on the other hand Slope is one kind of surface of which one end or side is at a higher level than another. Roads, embankment, end sides of the bridges & fly overs do consist slopes to stable the structures but more often slopes get affected by the erosion & occurs hazardous event & be the reason of massive structure failure.

Now we have to understand the relation between slope & erosion. In slopes of the structures water and gravity work together to cause erosion. Sometimes massive precipitation occurs which made the soil thoroughly soaked with water. Water made the slopes of the cliff so heavy and loosened that the bonds between particles of soil so much that the force of gravity caused whole parts of the slope to come loose and fall. This phenomena is called landslide. Other than that some other events which may triggered the mass movement in many ways as

• Undercutting of the slopes;
• Overloading of the slopes; 
•  Vibration from earthquakes that break the bond holding the slope in place.

Erosion on Slope

Erosion on Slope

Now we will discuss how we can control erosion in slope. There are many methods to control erosion as

1.            Plant grass and shrubs;
2.        Vegetation to slope;
3.          Build terraces;
4.          Create diversions to help drainage;
5.          Grassed waterways;
6.          Conservation ponds;
7.          Retaining wall.

Plant grass and shrubs are very effective at stopping soil erosion. This is primarily because plant roots tend to hold soil together, making it harder to erode. The leaves of the plants also help to reduce the velocity of raindrops falling on the ground, making it harder for them to dislodge the soil and erode it. Ornamental grass and low, spreading shrubs work best as they leave no areas of bare soil exposed to the elements.

Vegetation and slope stability are interrelated by the ability of the plant life growing on slopes to both promote and hinder the stability of the slope. The relationship is a complex combination of the type of soil, the rainfall regime, the plant species present, the slope aspect, and the steepness of the slope. Knowledge of the underlying slope stability as a function of the soil type, its age, horizon development, compaction, and other impacts is a major underlying aspect of understanding how vegetation can alter the stability of the slope. There are four major ways in which vegetation 

 influences slope stability: wind throwing, the removal of water, mass of vegetation (surcharge), and mechanical reinforcement of roots.

Terracing is the technique of converting a slope into a series of horizontal step-like structures  with the aim of:

• Controlling the flow of surface runoff by guiding the runoff across the slope and conveying it to a suitable outlet at a non-erosive velocity;

•           Reducing soil erosion by trapping the soil on the terrace;

•       Creating flat land suitable for cultivation

Terracing helps prevent the formation of rills, improves soil fertility through reduced erosion, and helps water conservation.

Diversions are ridges of soil or channels with a supporting ridge on the lower side. They are built across the slope to intercept runoff and dispose of it at a selected location. They are used to break up long slopes, to direct water away from active erosion sites, to direct water around agricultural fields or other sites, and to channel surface runoff to suitable outlet locations. Safe passage of the surface runoff to prevent slope failure can be achieved by installing drainage ditches, or by cross drainage work for road structures.

Grassed waterways are natural or artificially constructed water courses shaped or graded to the required dimensions and planted with suitable vegetation. Grassed waterways generally run down a slope and are designed to conduct surplus water safely into natural drainage courses. They are usually made broad and shallow, although the shape and size can vary depending on the size of the drainage area, slope of the land, and soil type. The channels help surface water to flow across the land without causing soil erosion. They are used as outlets to prevent rill and gully formation. The vegetation in the channel helps control the water flow and reduces channel surface erosion. Properly designed grassed waterways can safely transport large volumes of water to the down slope. They are also used as filters to prevent sediments entering into nearby water bodies. Grassed waterways are used as outlets for diversions and emergency spillways; to safely convey runoff from contour and graded bunds and bench terraces; as outlets for surface and sub-surface drainage systems on sloping land; to carry runoff from natural drains and prevent formation of gullies; and  to dispose of water collected in road ditches or discharged through culverts.

Conservation ponds, also known as farm ponds, are small reservoirs constructed to collect & store water from surface runoff. Storing water runoff during excessive rainfall helps to reduce the peak flow and surface erosion and thus reduce the probability of floods. It is also useful for providing supplemental irrigation for agriculture, water for domestic purposes, and fish farming. Conservation ponds play a significant role in areas with rainfed agriculture, and construction of a large number of ponds in a catchment area can have a significant effect.

Retaining walls are artificial structures that hold back soil, rock, or water from a building, structure, or area. Retaining walls prevent down slope movement and soil erosion, and provide support for vertical or near-vertical changes in gradient. The walls are generally made from timber, masonry, stone, brick, concrete, vinyl, steel, or a combination of these. Retaining walls act to support the lateral pressure exerted by a soil mass which may cause slope failure. Retaining walls are strongly recommended where the toe of slope has collapsed and the slope failure is likely to progress upward along the slope. Retaining walls should be constructed on a stable foundation. Retaining walls are categorized in two ways:

1. Based on the mechanics of performance,
2. Based on the construction material.

To control erosion in slope there is a various method which we previously discussed & among them to select a suitable method we have to analysis the site properly and adequate attention have to provide to some factors like climatic information, microsite evaluation and to know the type of soil.