Bench terraces are typically suitable for installation on slopy lands with a gradient ranging from 16.67% to 33%. This range represents the primary application area where these soil conservation structures are most effective for managing water runoff and preventing soil erosion.
Understanding Bench Terrace Applications
Bench terraces are a widely used soil conservation practice, characterized by a series of level or nearly level platforms constructed across a slope, separated by steep risers. Their primary purpose is to reduce the effective length of a slope, thereby decreasing the velocity of runoff water and promoting infiltration.
- Primary Slope Range (16.67% - 33%): This is the optimal slope range where bench terraces are generally constructed to create arable land on hilly terrains and effectively control erosion. They are particularly well-suited for areas where soil depth exceeds 2.5 feet, allowing for sufficient material to be moved to form the benches without exposing infertile subsoil.
- Application in Highly Slopy Lands (8% - 15%): Even in less extreme "highly slopy lands" (e.g., 8-15% slope), specific types of bench terraces are strategically planned. The design—whether horizontal, inward-sloping, or outward-sloping—is chosen based on factors such as soil type, the intensity of expected rainfall, and the land's water-holding capacity.
Types of Bench Terraces for Diverse Slopes
The choice of bench terrace type depends heavily on the specific gradient, soil characteristics, and local climatic conditions. Here's a look at how different slopes dictate the design:
| Slope Range | Typical Application for Bench Terraces | Specific Bench Terrace Designs Often Used |
|---|---|---|
| 16.67% - 33% | General suitability for effective soil and water conservation, creating flat farming areas. | Standard Bench Terraces (Level, Graded) |
| 8% - 15% | Application in "highly slopy lands" requiring precise erosion control. | Horizontal, Inward, Outward Bench Terraces |
| Greater than 33% | May require more intensive and specialized engineering, or other conservation methods. | (Less common for standard bench terraces) |
Practical Insights into Bench Terrace Design
- Horizontal Bench Terraces: These are ideal for areas with permeable soils and low rainfall, designed to retain all precipitation on the terrace for maximum infiltration.
- Inward-Sloping (Graded) Bench Terraces: Common in regions with high rainfall and less permeable soils. The slight inward slope directs excess water towards a stable grassed waterway or outlet, preventing accumulation and potential erosion of the riser.
- Outward-Sloping Bench Terraces: Less common and typically used on very stable soils or for specific crops. They are designed to shed excess water away from the riser, though this can increase erosion risk on the outer edge if not properly managed.
Bench terraces are a crucial tool in sustainable agriculture, offering a long-term solution for cultivating steep landscapes while protecting valuable soil resources. For more detailed information on terrace farming and its benefits, resources from organizations like the Food and Agriculture Organization of the United Nations (FAO) offer extensive insights.
