Impacts of Historic Land-use on River Channels and Floodplains


Figure 4. Little Tennessee River cutbank showing historic and prehistoric strata, and the position of a radiocarbon date of 770 BC. Long-term average sedimentation rates in the prehistoric strata are about 0.5 mm/y versus 5.0 mm/y in the historic strata.

The focus of this research is on changes in river channel morphology and bottomland sedimentation patterns in the upper Little Tennessee and French Broad River systems. These rivers and their wide alluvial valleys underwent pronounced changes beginning in the late 1700s. The changes steadily increased through the mid to late 1800s as widespread agricultural and timber-harvesting activities accelerated erosion and sedimentation across the region (Ayres and Ashe 1905, Glenn 1911). Subsequent changes in land use played an equally important role in the ongoing and complex sequence of fluvial landscape response and recovery. Preliminary observations and a radiocarbon date from an exposed stream bank (Figure 4) indicate prehistoric sedimentation rates of 0.5 mm/y, and 5.0 mm/y since 1800. Preliminary calculations suggest major morphological changes in floodplains following European settlement. We anticipate these changes can be linked to flood frequency, and ecological interaction between the channel and its floodplain.

We will address the following questions:
1. What is the chronology, frequency, and magnitude of floods and their interactions with vegetation and land use?
2. What is the rate of sediment accumulation and related changes in channel morphology?
3. What are the impact signatures of distinct disturbance regimes?

Previous Research on Topic

Investigators
Paul Bolstad, University of Minnesota, Forest Processes
Fred Benfield, Virginia Polytechnic Institute & State University, Stream Processes
Ted Gragson, University of Georgia, Human Disturbance Processes
David S. Leigh, University of Georgia, Geomorphic Process
Mark Riedel, USDA-USFS, Hydrology
Bruce Wallace, Universtiy of Georgia, Stream Processes
David Wear, USDA-USFS, Forest Economic Modeling
Jack Webster, Virginia Polytechnic Institute & State University, Stream Processes