Sedimentation and Soil Erosion Control Techniques during construction Phase

 

Sedimentation  and soil erosion control measures:

During construction stage, the soil gets unconsolidated due to removal of stabilizing agents like vegetation and due to disturbance to stable slopes. This results in loss of fertile topsoil and deposition of the same in undesired area of site or it gets washed away with runoff.

What is top soil and Why is it important?

As per National Building Code of India,  the top 200 mm of the soil is considered as top soil.

Top soil consists of humus(decayed organic matter) which is helpful in plant growth. It consists of useful soil organisms and nutrients. It also helps in rain water percolation  to ground and helps in storing the storm water in the soil.

Sedimentation Basin:

Sedimentation basin is a temporary basin or collection tank at the lowest point of the site to collect and detain  storm water runoff to settle the sediments.  This arrangement with desired retention time will settle most of the sediments before the runoff is directed to the outfall.

Contour Trenching(suitable for areas with slopes greater than 10% or 1 V: 10 H):

Contour trenching is the arrangement of ridge and trench system parallel to the contours of the place. 

This arrangement reduces the velocity of runoff and increases the distance of overland runoff flow.

This in turn captures most of the sediments and reduces soil erosion.

Growing vegetation or native grass in the trenches and on ridges (earthen bund) will help in stabilizing the slope.

Refer here for Construction and dimensions of contour trenches