The timing, intensity, and duration of the river s flooding of the Delta, collectively known as the hydroperiod, ultimately have the foremost impact on the species composition, structure and function of the wetland s plants. Floods in the spring and summer months have a greater impact on tree survival and plant growth than flooding in the fall and winter. The movement of water traveling along rivers through the floodplain causes a constant process of natural sediment erosion and deposition, producing numerous variations in wetland habitats. The meandering river channel produces oxbow lakes that develop into deepwater alluvial swamps. Sloughs form in meander scrolls.
Sand bars form on the inside of river curves.
Natural levees form where coarse sedimentary material settles out along the river channels as floodwaters recede, while backwater areas, or backswamps, often form in depressions located between the natural levees and valley walls. Each of these variations of wetland habitat has specific soils and elevations, and thus distinct periods of inundation by water. The combination results in specific plant species, and hence discrete plant and animal communities. Starting at the northern end of the Delta, the Alabama and Tombigbee Rivers form a long peninsula of over 36,000 acres of the most extensive area of seasonally flooded natural levee bottomland hardwoods in Alabama. This area, called Fork of Rivers, is perhaps one of the most extensive intact examples of this wetland community type left in the entire southeastern United States.