Evaluation of the Effects of Hydrologic and Geomorphic Processes and Bottomland Hardwood Plant Communities of the Lower White River Basin: An integrated approach
August 2010 - May 2014
- Memphis District
The lower White River, Arkansas is a RAMSAR Wetland of International Significance that supports the largest concentration of wintering mallards in North America, the second largest tract of bottomland hardwood forests in North America, and the most productive warm water fisheries in the southeastern United States. However, the hydrologic and geomorphic processes of the White River have been affected by numerous developments within the watershed, as well as that within the Mississippi River (Biedenharn and Watson 1997). Base-level lowering of the Mississippi River (Biedenharn and Watson 1997), a series of hydroelectric dams upstream, a navigational lock at its confluence with the Mississippi River, a navigation channel along much of its course, and an irrigation pump that diverts surface water from the river affect present river conditions. Rivers are process-response systems that fluctuate around an “endpoint” of dynamic equilibrium. Changes in sediment load, channel depth, and discharge, among other parameters, can result in rapid changes in the river and associated floodplain. For example, dredging can lead to channel incision which progresses upstream until a new dynamic equilibrium is reached with a new slope. Incision can also cause bank instability and a lowering of groundwater tables, thus accelerating forest loss along banks, decreasing tree growth, and altering forest species composition. Thus, an understanding of the relationship among present and future (predicted) geomorphic processes, surface and subsurface hydrologic processes, and tree growth and establishment is critical for evaluating the effects of future development activities within the watershed. Because of the interconnectedness of these complex systems, examination of hydrologic, geomorphic, or vegetative components in isolation of the others may lead to erroneous conclusions and unreliable predictions of future conditions. In this study, we will: 1) Identify historic and current rates of channel incision, bank erosion, and meandering; 2) Determine bank heights along the river from Montgomery Point to Devalls Bluff; 3) Determine sedimentation rates along three sections of the floodplain (i.e., Devall’s Bluff to confluence of Cache, Clarendon to St. Charles; St. Charles to Montgomery Point); 4) Determine surface and subsurface hydrologic processes along three sections of the floodplain; 5) Determine growth rates and stand establishment of bottomland hardwoods within selected plant communities along three sections of the floodplain; 6) Develop an integrated, spatially-explicit, multi-scale simulation model to determine the effects of current and potential hydrologic processes on the distribution of bottomland hardwood plant communities on the floodplain of the White River.