| Hydrology of Forested Wetlands in the Atchafalaya River Basin |
PRESENTATION
Richard H. Day and Thomas W. Doyle dayr@usgs.gov
U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Blvd., Lafayette, LA, 70506
Abstract
The Atchafalaya basin floodway is bordered by high levees to protect the surrounding landscape from flooding. The basin is also divided into sub‐basins bounded by lower natural and artificial levees. Water flow through the basin tends to be channelized. Hydrological exchange between sub‐basins and major channels occurs during high water overbank flooding as well as in small channels which reverse flow regularly to fill and drain the sub‐basins with the passing of flood peaks. This limited exchange results in stagnation and hypoxic conditions, and the forested wetlands within the sub‐basins are waterlogged for long periods of time. Hydrology within the forests is also influenced by rainfall, evapotranspiration, and subsurface drainage. We examined long term records of water level gages in the Atchafalaya River and other in‐channel gages and compared them to data collected from continuous water level recorders we installed within the forested wetlands to measure flooding above the surface of the forest floor. We compared hydroperiods within the forests to the hydrograph of the nearest source of riverine input to gain an understanding of the range of conditions within the forested environments in relation to the river connectivity of each site. The seasonality, depth, and duration of flooding within the forested wetlands control the composition of forest species and the flow of nutrients for sustained productivity. Riverine input also delivers sediment, which by its deposition causes gain in elevation, lowering flooding frequency and forcing change in forest composition. |
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