What role do retainment basins play in stormwater management?

Retainment basins are crucial components in stormwater management because they are specifically designed to hold stormwater runoff. By doing so, they provide the necessary time for sediment and pollutants present in the water to settle at the bottom of the basin. This process greatly improves water quality before the water is eventually discharged into nearby bodies of water or drainage systems.

The retention feature is essential in reducing the flow rate of stormwater, thereby minimizing potential flooding and erosion downstream. In addition, it helps in filtering out contaminants, improving overall water quality, and supporting aquatic ecosystems.

In contrast, the other options do not reflect the fundamental role of retainment basins. While decorative features may enhance a landscape, they do not contribute to stormwater management. The collection of trash is not the primary function of a retainment basin; instead, focus is on sediment and pollutant removal. Lastly, retainment basins are designed to reduce rather than increase runoff, ensuring better control over stormwater discharges.