What characterizes the back swamp area behind a levee?

The back swamp area behind a levee is characterized by being poorly drained due to the levee's presence. Levees are designed to control flooding by keeping river water contained during high flow events. However, this containment can lead to increased water retention in the back swamp area, where drainage is limited. As a result, the back swamp often experiences prolonged periods of saturation, leading to the development of wetland conditions. This poor drainage can create an environment that is conducive to the accumulation of standing water and specific wetland vegetation, but it primarily impacts the water movement and drainage capabilities of the area, underscoring its classification as poorly drained.

In contrast, the other characteristics mentioned in the other options do not apply to a back swamp. For example, the area is not typically regarded as well-drained or flowing freely; it actually tends to retain water. Additionally, while it might support specific wildlife and plant species adapted to wetland conditions, it is not universally recognized as rich in wildlife in the same way other ecosystems might be. The collection of sediment from upstream sources generally occurs in river beds and floodplains rather than specifically in back swamp areas, where water dynamics are influenced more by the levee system.