NASCLA Accredited Commercial General ContractorSite WorkMedium
A construction site is located on a steep slope with erodible soil. During heavy rainfall, there is a risk of significant soil erosion and sediment runoff into a nearby stream. Which of the following temporary erosion control measures is most effective for slowing down concentrated runoff and promoting sediment deposition at the base of the slope?
- ASediment trap/basin
- BErosion control blankets
- CSilt fence
- DCheck dam
Show answer & explanationAnswer & explanation
Correct answer: A. Sediment trap/basin
A sediment trap or basin is designed to collect and detain sediment-laden runoff, allowing the sediment to settle out before the water is discharged. This is highly effective at the base of slopes where runoff concentrates.
Why the other options are wrong
- B. Erosion control blankets are for protecting the slope surface itself, not for collecting concentrated runoff at the base.
- C. Silt fences are for sheet flow and smaller drainage areas, not concentrated runoff at the base of a steep slope.
- D. Check dams are used in ditches or swales to slow down water flow and promote minor sediment deposition, but a trap/basin is more suitable for significant concentrated runoff.
Sediment Trap/Basin
A temporary erosion and sediment control structure designed to detain sediment-laden runoff, allowing suspended solids to settle out before the water is discharged, typically used at the base of slopes or outfalls.
- Detains concentrated runoff.
- Allows sediment to settle.
- Effective at base of slopes or drainage points.
Memory trick: Protecting soil needs layers: surface, flow, and collection for the sediment's stay.