|Since the turn of the century, county, state and federal agencies have straightened, deepened, widened and leveed portions of nearly all of the large rivers in West Tennessee along with many of their tributaries. Among other things, these channel modifications were made to accelerate storm water drainage, to increase overbank flood stage, to protect agricultural land from flooding and to lower the water table in bottomland areas, thereby increasing the acreage suitable for cultivation.
The effects of channelization on ecosystem conditions and processes within a river and its associated riparian zone are diverse and vary geographically due to variability in factors such as climate, soil, channel morphology, and drainage basin characteristics. In western Tennessee, sediment inputs from overland transport off agricultural fields as well as headcutting and lateral bank failures of channelized tributaries have led to channel aggradation and the formation of valley plugs in main stem rivers. Channel blockages, in turn, increase the depth, area and duration of seasonal flooding, alter sediment deposition patterns and produce vegetational changes over extensive areas of adjacent valley bottoms. The creation of levees, which further isolate floodplains from their associated lotic systems, have exacerbated these changes in ecosystem structure and function by trapping overflow moving across the floodplain surface. These hydrogeomorphic adjustments have forced federal and state authorities to rechannelize or redredge stream reaches as a means of hydrologic management. However, due to concerns about the ecological impacts of channelization and a growing desire to improve wetland ecosystem functions, managers are increasingly searching for alternatives to reworking the modified channel.
|A channelized stream in western Tennessee. Notice the old meander on the left of the channel.|
|Our research involved examining the functions of rivers that had been channelized compared to those that had not. We examined nutrient pools, hydrology, and forest composition and structure.|
|An older pecan floodplain in the Tigrett WMA.|
|Publications from this research:
Franklin, Scott B., John A. Kupfer, S. Reza Pezeshki, Randy Gentry & R. Daniel Smith. 2009. Complex effects of channelization and leveeing on western Tennessee floodplain forest structure, composition and function. Wetlands 29:451-464. PDF
Franklin, Scott B., John A. Kupfer, Reza Pezeshki, Randall W. Gentry & R. Daniel Smith. 2009. Efficacy of the hydrogeomorphic model: a case study from western Tennessee. Ecological Indicator 9:267-283.
Franklin, Scott B., John A. Kupfer, S. Reza Pezeshki, Tanya Scheff, Ryan Hanson & Randy Gentry. 2001. Floristic, edaphic, and hydrologic conditions of Stokes Creek, TN prior to dechannelization. Physical Geography 22:254-274. PDF
Franklin, Scott B., John A. Kupfer, S. Reza Pezeshki, Natasja van Gestel & Randy Gentry. 2001. Channelization effects on floodplain functions in western Tennessee. Pp. 189-201 In: R.A. Falconer & W.R. Blain (eds.) River Basin Management, WITpress, Southampton, Boston.