Which materials can be used to construct check dams in grass channels?

Which materials can be used to construct check dams in grass channels?

• A. Plastic sheeting
• B. Wood, gabions, riprap, or concrete underlain with filter fabric
• C. Steel
• D. Concrete blocks

Answer: (B)

In grass channels, check dams should slow flow, trap sediment, and stay stable without cutting off natural vegetation or causing downstream erosion. Materials that are sturdy yet permeable and can be anchored or tied together work best, especially when paired with a filter fabric underneath to keep fines from washing through. Wood, gabions (wire baskets filled with rock), riprap (rock armor), or concrete set underlain with filter fabric provide the right balance: they create roughness to reduce velocity, offer structural resistance to being displaced by flow, and, with the fabric, prevent piping of fine soils so the dam remains effective over time. Other options fall short for these uses. Plastic sheeting is impermeable and not durable in a channel environment, making it prone to tearing and failure. Steel can corrode and become unstable in wet, soil-packed conditions, and it often isn’t as adaptable or easy to maintain in grassy channels. Concrete blocks alone may be heavy and rigid, can shift or create concentrated flow paths, and typically don’t incorporate a sediment-controlling fabric as part of the dam assembly.

In grass channels, check dams should slow flow, trap sediment, and stay stable without cutting off natural vegetation or causing downstream erosion. Materials that are sturdy yet permeable and can be anchored or tied together work best, especially when paired with a filter fabric underneath to keep fines from washing through. Wood, gabions (wire baskets filled with rock), riprap (rock armor), or concrete set underlain with filter fabric provide the right balance: they create roughness to reduce velocity, offer structural resistance to being displaced by flow, and, with the fabric, prevent piping of fine soils so the dam remains effective over time.

Other options fall short for these uses. Plastic sheeting is impermeable and not durable in a channel environment, making it prone to tearing and failure. Steel can corrode and become unstable in wet, soil-packed conditions, and it often isn’t as adaptable or easy to maintain in grassy channels. Concrete blocks alone may be heavy and rigid, can shift or create concentrated flow paths, and typically don’t incorporate a sediment-controlling fabric as part of the dam assembly.