Difference between Contour Bunding and Graded Bunding
The major differences between Contour Bunding and Graded Bunding are given in the table below:
Low annual rainfall (< 600 mm)
They are used in areas having annual rain greater than 700 mm.
Suitable for permeable soils such as alluvial, red/laterite brown soil, and shallow and medium black soil.
Good for impenetrable soil.
It is commonly used on farming land up to 6% slope.
Not appropriate on land slopes less than 2% or on slopes greater than 8%.
Found in Maharashtra, Gujarat, Tamilnadu, Karnataka, and Andhra Pradesh.
Found in hilly areas, like Dehradun.
Contour Bunding vs Graded Bunding
Contour Bundin aids in the capture and retention of rainfall before it becomes runoff. Graded bunding is used to create obstacles across the path in order to retain water flowing through the watershed and thus help control soil erosion.
Contour Bunding entails constructing earthen dams across the slope of the land, as closely as possible following the Contour. The area is divided into strips by a series of bunds, which reduces the velocity of the water runoff.
Graded bunds, graded terraces, or channel balconies are laid along a pre-determined longitudinal incline near the Contour but not precisely along the shape. These terraces act as drainage canals to control and conduct runoff at non-erosive velocity.