T169 Perspectives in Floodplain System Science (Posters)

Tuesday, 6 November 2012
9:00 AM - 6:00 PM
Hall B

EVOLUTION OF A MEANDER BEND ON THE CATAWBA RIVER NEAR CHARLOTTE, NC

Paper number: T169-3
Program: Technical Sessions
Time: 9:00 AM – 6:00 PM

Authors

Abstract

The formation of oxbow lakes during meander neck cutoff events is a common fluvial process in sinuous, low gradient streams. Based on analysis of topographic maps and aerial imagery, it appears that Duck Cove, near Charlotte, NC, may be an oxbow lake formed by the straightening of the Catawba River. Duck Cove is a crescent-shaped, shallow body of water adjacent to the Catawba River, to which it is connected at its downstream end by a narrow tie channel. The upstream end of the cove is cut off from the Catawba River by sediment filling the upstream end of the former meander bend. The floodplain between the cove and the river is characterized by low ridges and swales interpreted as scroll bars on the former point bar. In this study vibracoring and GPR were used to examine these possible point bar and channel fill deposits.

Three facies occur in the cores, from oldest to youngest: 1) a fining upward sequence of medium to fine sand (point bar deposits), 2) an organic-rich silt to very fine sand (oxbow lake deposits), and 3) thinly bedded, medium to coarse sands at the top of the cores (crevasse splay deposits on the modern flood plain). Analysis of aerial imagery and GPR profiles suggest the presence of an abandoned channel which is consistent with the interpretation that Duck Cove is an oxbow lake. C14 dating of one charcoal sample from the oxbow lake deposits provides a minimum age for the cutoff event and subsequent formation of the oxbow lake at 5377 +/- 60 years BP. Previous work which uses terrace relief (i.e. terrace elevation – river elevation = terrace relief) as a proxy for age places the cutoff event at less than 4000 years BP (Layzell, 2012). The results of this study suggest that the regional curve for terrace relief (Mills, 2000; Figure 1) needs refinement for relatively young terrace deposits.