Terrace & WASCOB
Practice Overview
Terraces and Water and Sediment Control Basins (WASCOBs) are systems of ridges that are built on hillsides to slow, collect, and divert surface runoff to prevent erosion. Designs vary by site, based on topography and land use, but the main difference between terraces and WASCOBs is that terraces are designed to cross multiple water courses, while WASCOBs use smaller embankments and a system of intakes and pipes. Both are recognized as soil conservation methods that are eligible for NRCS funding.
Benefits
These soil conservation methods provide many benefits for irregular topography or sloped fields, including:
- Reducing erosion
- Reducing surface runoff
- Capturing sediment
How It Works
In farmable fields with moderate to high slopes, both methods use similar systems a system of ridges/embankments is used to block the path of surface runoff. The water is diverted to a designated area where it can flow downhill over a much less erodible surface such as a grassed waterway. Water is slowed, which reduces sheet erosion, and gully erosion is minimized when water is diverted to a designated waterway.
WASCOB designs are meant to block the water, hold it in a basin, and slowly release it through an underground pipe system. This allows sediment and debris in the surface water to settle out before moving downstream, which reducing nutrient and sediment transport.
Depending on the site and design, the ridges can be shallow enough to farm atop and minimize the loss of production acres.
Installation Considerations
- Most efficient on fields with slopes of 2% to 18%
- Ideal for sites with irregular topography
- Requires fertile soil without shallow bedrock
- Plan for the working width of farm equipment
- Must be maintained to limit buildup of sediment and debris