ARS | Publication request: Sediment Source Tracking in the Georgia Piedmont

Submitted to: Georgia Water Resources Conference
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 20, 2009
Publication Date: N/A

Interpretive Summary: Many streams in the United States do not meet the water quality standards set forth by the EPA because of high sediment load. It is not clear if the reason for the high levels of sediment is due to current upland erosion sources (such as agricultural fields, roads, ditches, and construction sites) or streambank erosion. The growing concern on the effect of fine sediment on water quality has resulted in the need for better and effective sediment control strategies for water quality improvement at watershed scales. The objective of this study was to determine if the present load of sediment in a Georgia Piedmont watershed is from surface soils or stream banks. Radioactive fallout (137Cs) and three natural tracers (N, C, P) were used to estimate the relative contribution of streambank and upland sediment sources and analyzed in a mixing model. The model prediction using each tracer was used to determine the relative contribution of streambanks compared to upland sources. Our preliminary results indicated that about 90% of the suspended sediment in the streams came from the streambank material and therefore management efforts should concentrate on controlling streambank erosion. Better understanding on the sources of suspended sediment in streams has practical implications on the type of best management practices to implement for sediment control.

Technical Abstract: Preliminary results on the source of suspended sediment in a southern Piedmont stream are presented. Nuclear fallout radionuclide 137Cs and three other natural tracers were used to estimate the relative contribution of bank and upland sediment sources. Tracer concentrations were determined in potential sediment sources and suspended sediment samples collected from the stream and analyzed in a mixing model. Uncertainty in model prediction was accounted for by using a Monte Carlo simulation approach. Our preliminary results indicated that about 90% of the suspended sediment in the streams emanated from the stream bank material. We assume that the results are applicable to other watersheds in the southern Piedmont. Better understanding on the sources of suspended sediment in streams has practical implications on the type of sediment control measures to be adopted. Investment of resources in improving water quality should consider the contribution of bank erosion to water quality impairment.