Step 1: Understanding the Concept:
Bench terraces are a soil and water conservation measure used on steep slopes to reduce erosion and allow for cultivation. They convert a steep slope into a series of flat or nearly flat steps. The design of the bench (level, outward sloping, or inward sloping) depends on the rainfall and soil conditions. The question asks for the suitable type in high rainfall areas with steep slopes.
Step 2: Detailed Explanation:
Let's analyze the different types of bench terraces:
(A) Outward sloping bench terrace: The bench is sloped slightly outwards, away from the original hillside. This design encourages runoff to flow over the edge of the terrace. It is only suitable for low rainfall areas with permeable soils, where excess water is not a major issue and erosion from the overflow is minimal.
(B) Level bench terrace: The bench is perfectly flat. This design is intended to impound all the rainfall that falls on it, promoting maximum water conservation through infiltration. It is suitable for low to medium rainfall areas with highly permeable soils that can absorb the impounded water. In high rainfall areas, they would get waterlogged and could fail due to overtopping.
(C) Inward sloping bench terrace: The bench is sloped slightly inwards, towards the original hillside. A channel is constructed at the inner edge to collect the runoff. This channel then safely conveys the excess water along the terrace to a protected outlet (like a grassed waterway). This design provides excellent control of runoff and prevents erosion. It is specifically recommended for high rainfall areas and/or areas with less permeable soils, where it is essential to safely dispose of excess runoff from heavy storms.
(D) Tati terrace: This is not a standard classification of bench terraces in soil conservation engineering.
Step 3: Final Answer:
For high rainfall areas with steep slopes, where safe disposal of excess runoff is the primary concern, inward sloping bench terraces are the appropriate choice. Therefore, option (C) is the correct answer.