Which structure is designed to allow sediments to settle out before water is released?

The sediment basin is specifically designed to capture and retain runoff water, allowing sediments to settle out before the water is released. This structure temporarily holds stormwater, providing sufficient time for particulate matter, such as soil and debris, to settle to the bottom. As the settled materials accumulate, they are stored in the basin until maintenance is performed to remove the buildup, thus ensuring clarity of the outflow water and preventing sediment from entering downstream water bodies.

In contrast, a sediment trap typically captures sediments but does not hold water for as long as a sediment basin, making it less effective for larger volumes of runoff. A retention pond is designed to hold water permanently and can facilitate some settling; however, its primary function is to provide water storage for various uses, not specifically for sediment control. A detention basin, on the other hand, temporarily holds stormwater and slowly releases it, but its primary function is flood control rather than sediment control. Therefore, for the specific goal of letting sediments settle out before water is released, the sediment basin is the most appropriate structure.