Contour Bunding
Terminology
- Bunding is a mechanical technique of reducing run off. It also helps in collecting water for longer time to help infiltration into the ground.
- There are two types of bunding
- Block Bunding – uses large blocks across sloping lands, can be of stones or earth or both
- Contour Bunding – only uses earth in most cases and the height is also less. Thus, it is used in gently sloping lands
- It will be good to note at this juncture, that there are many closely related terminology like Contour bunding, contour ploughing, terrace farming, compartmental bunding, graded bunding, peripheral bunds etc. They are used in different contexts and vary from each other. (See a simple pictorial description below)
Contour Bunding – It consists of building earthen embankments across the slope of the land, following the contour as closely as possible. A series of such bunds divide the area into strips and act as barriers to the flow of water, thus reducing the amount and velocity of the runoff.
- Graded Bunding – Graded bunds or graded terraces or channel terraces are the bunds or terraces laid along a pre-determined longitudinal grade very near the contour but not exactly along contour
- Peripheral Bunding – Bunds area also constructed along field boundaries without reference to contour. These bunds are called peripheral bunds. They serve as fences, and give protection from water and wind erosion in low rainfall areas. They are not suitable in heavy rainfall areas.
- Contour Ploughing – involves making no bunds but ploughing at ninety degree to the slope of the land
- Terrace Farming – it alters the slope of the area and produces flat areas.
Design Considerations
- Allowable submergence of land according to crop
- Moisture Conservation
- Economy of Construction
- Critical Length
- Seepage Consideration
Areas Practiced
- Contour Bunding are carried out in many parts of India – notably in Maharashtra, Gujarat, Tamilnadu, Karnataka and Andhra Pradesh.
- It doesn’t work with black soil, on account of its contraction in dry situations, leading to cracks.
Other Uses
- Contour Bunding and other methods has emerged as an effective watershed management tool
- It not only helps in prevention of soil erosion but also helping creating water pools for rejuvenation of ground water.
- The same technique is also used during forest plantation on slopes.
- Crescent shape depressions are made near the roots of trees which help in sinking of the water in the roots of trees
- Crops like castor oil can be planted on bunds which can give extra income and also hold the bunds.
- Deep rooted grass can also be used for above purpose and can act as fodder for livestock.
