Water and Sediment Control Basins (WASCOBs)
Water and Sediment Control Basins (WASCOBs) function similarly to terraces but are typically shorter and straighter, placed at the low end of slopes to manage water runoff and prevent gully erosion. While terraces reduce slope length, WASCOBs are designed to capture and store runoff, allowing sediment to settle before water is slowly released through tile drainage or infiltration.
How WASCOBs Work
These basins temporarily hold runoff, reducing the speed of water flow and delaying flood peaks. As water settles, soil particles and nutrients separate from the water, preventing sediment from entering nearby water bodies. To remain effective, WASCOBs require periodic maintenance, including sediment and debris removal. Unlike terraces, which follow the natural slope of the land, WASCOBs are often placed in drainageways and are more effective on irregular landscapes.
Benefits and More Resources
WASCOBs reduce gully erosion, improve water quality, and help retain valuable soil nutrients. According to Iowa State University, they reduce total solids by 80% and phosphorus by 85%. Additionally, they allow for farming on upstream areas when not actively holding runoff. However, they require initial investment, regular maintenance, and proper design to prevent overflow-related erosion issues.
Farmers can work with conservation specialists to determine if WASCOBs are the right fit for their fields. Iowa State University Extension and outreach has done great work on this topic. Learn more about it here.