Contour bunding is an important soil and water conservation practice in India. In which type of physical environment is contour bunding most appropriately and commonly used?

Introduction / Context:
Contour bunding is a soil and water conservation technique used widely in agriculture to reduce soil erosion and increase moisture retention. It involves constructing embankments or bunds along lines of equal elevation, that is, along contours. Understanding where this method is most effective helps in planning watershed management. This question asks in which type of environment contour bunding is primarily used.

Given Data / Assumptions:
• The method mentioned is contour bunding, a practice of building bunds along contour lines. • Options describe different environments: scrublands, hilly or sloping areas, low flat plains near streams and desert margins. • We assume typical Indian agricultural and land management practices. • The aim is to reduce erosion and slow runoff where it is most problematic.

Concept / Approach:
Contour bunding works by intercepting surface runoff on slopes. When rain falls on sloping land, water tends to flow quickly downhill, carrying soil with it and causing erosion. Bunds built along contour lines break this flow, reduce the speed of water, encourage infiltration and trap sediments. Therefore, contour bunding is especially suitable for hilly and sloping terrain. On flat plains there is less slope and more risk of flooding, where other measures like embankments or drainage channels are used. In desert margins wind erosion is more important than water erosion, so vegetative barriers and windbreaks are more appropriate.

Step-by-Step Solution:
Step 1: Recall that contour means a line of equal elevation on a map and that bunds built along such lines are aligned horizontally across the slope. Step 2: Understand that the main purpose of contour bunding is to reduce water runoff and soil loss on sloping ground. Step 3: Identify hilly and sloping or mountainous areas as places where runoff is strong and erosion potential is high. Step 4: Recognise that low flat plains near streams experience flooding more than slope related erosion, so other flood control measures are used. Step 5: Note that desert margins are dominated by wind erosion rather than sheet runoff, so windbreaks and shelter belts are more relevant. Step 6: Therefore, hilly and sloping or mountainous areas are the correct environment for contour bunding.

Verification / Alternative check:
Agricultural engineering manuals and soil conservation guides consistently describe contour bunding as a practice for sloping lands, particularly in rainfed hill agriculture and upland farming. Case studies from the Deccan plateau, central India and Himalayan foothills show implementation of contour bunds to check soil erosion. In contrast, flood plains are treated with levees and drainage works, and desert margins with sand dune stabilisation techniques, not primarily contour bunds.

Why Other Options Are Wrong:
Scrublands liable to weed growth do not define a specific erosion process by themselves and may require grazing management rather than contour bunding. Low flat plains close to stream courses are more prone to flood inundation than rapid runoff down slopes, so contour bunding is not a primary method there. Desert margins are mainly affected by wind erosion, where techniques like shelter belts, strip cropping and sand dune stabilisation are more effective than contour bunding.

Common Pitfalls:
Some students mark desert margins because they associate soil conservation with any erosion prone area, without distinguishing between water and wind erosion. Others think low plains near rivers are always the focus of soil conservation without considering the problem of slope. The key to answering such questions is to match the technique to the main erosive force: contour bunding is specifically designed for water erosion on slopes.

Final Answer:
Contour bunding is mainly used in hilly and sloping or mountainous areas prone to runoff.