Which of the following would most likely be found in an extended detention basin as a sediment management feature?

• A. Sediment forebay
• B. Inflow pipe
• C. Vegetation buffer
• D. Outlet channel

Answer: (A)

Extended detention basins use a sediment forebay at the upstream end to manage sediment. This shallow pocket traps heavier solids as water first enters the basin, so most of the sediment settles there before the water flows into the main detention area. It protects the outlet structure, reduces fine-sediment carryover, and makes maintenance easier since the forebay can be dredged separately. Inflow pipes simply bring water in, vegetation buffers stabilize and filter along the edges, and outlet channels carry water out after detention—they aren’t sediment-trapping features inside the basin. The forebay is the design element specifically placed to capture sediment first, making it the best choice.