A Sediment Budget for Town Creek Watershed: Preliminary Results from Streambank Erosion Processes and Rates Assessment.

Abstract

Increased streambank erosion results not only in accelerated sediment yield, but also destabilizes streams with associated changes in stream type. This document reports preliminary results from a study which main objective is to evaluate streambank erosion rates and generate empirical correlations to estimate streambank erosion involving physical, geometric, and morphologic variables in the Town Creek watershed in Mississippi. A combination of methods is used for the study including field reconnaissance and detailed data collection, surveying, and channel modeling. Higher rates of increase in sediment load and yield from the northern headwaters were observed from unstable active streambank profiles near agricultural lands and limited or with no presence of riparian vegetation. Streambank failure events at these channels tend to be periodic, most frequently occurred during stormflow events season. Channel morphology changes from incised V-shaped channels to wide U-shaped channels with an increase in riparian vegetation density along the middle 20-km of the principal channel. Streambank erosion pins were installed on two representative places along the middle 20-km of the principal channel. Streambank erosion rate was assessed by measuring the length of the exposed pins after stormflow events on each plot. Assessment showed sediment deposition in most of the pin erosion plots. Jet testing results described streambank soils with high and very high potential to be eroded. Combined preliminary results, watershed characterization and field observation initially point to season and channel morphology as the more important factors affecting streambank erosion and deposition rates on streambanks and streambeds.