NASCLA Accredited Commercial General ContractorSite WorkMedium
A construction site is located on a steep hillside, and heavy rainfall is anticipated. To prevent erosion and sediment runoff into a nearby stream, the project manager decides to install a series of temporary measures along the contour of the slope. Which of the following erosion control measures is most appropriate for slowing runoff and trapping sediment on a hillside?
- ACheck dam
- BSilt fence
- CErosion control blankets
- DRiprap
Show answer & explanationAnswer & explanation
Correct answer: A. Check dam
Check dams are small, temporary barriers constructed across a swale or drainage ditch to slow the velocity of concentrated stormwater flow, thereby reducing erosion and allowing sediment to settle out. They are effective on slopes.
Why the other options are wrong
- B. Silt fences are for sheet flow on relatively flat areas, not concentrated flow on a steep hillside.
- C. Erosion control blankets are used to stabilize soil and promote vegetation growth on disturbed slopes, but they don't primarily function as sediment traps in concentrated flow paths.
- D. Riprap is used for permanent stabilization of channels or slopes against high-velocity flows, not typically as a temporary sediment trap.
Check Dam
A small, temporary or permanent barrier constructed across a swale, drainage ditch, or channel to reduce the velocity of concentrated stormwater flow, prevent erosion, and promote sediment deposition.
- Reduces flow velocity.
- Promotes sediment settling.
- Commonly made from rock, logs, or sandbags.
Memory trick: Fences for Sheet, Dams for Ditches, Blankets for Bare, Riprap for Rush.