Sediment Provenance and Transport in a Mixed Use, Mid-sized, Impaired Mid-Atlantic Watershed, Saucon Creek, Pennsylvania
- ISBN-10
- 1267372745
- ISBN-13
- 9781267372741
- Pages
- 88
- Language
- English
- Published
- 2012
- Author
- Rachel T. Baxter
Description
The Saucon Creek watershed in eastern Pennsylvania drains approximately 150 km2 of mixed use land that includes a significant legacy impact of mill dams and mill pond sediments. The watershed is impaired and undergoing a TMDL study driven by the hypothesis that high sediment loads are responsible for the impairment. The watershed has been instrumented to create a sediment budget in the context of its hydrology and response to storm events over summer and fall seasons of 2011, including many typical smaller to mid-size storms and a few extreme events such as the recent Hurricane Irene on 28 August 2011. A specific goal is to produce a model which links suspended sediment to turbidity given that turbidity is an easier proxy for continuous measurements over time including through flood hydrographs. Suspended sediment provenance is being assessed through a fingerprinting approach using the fallout radionuclide 210Pb. Sampling and sediment processing in the radiogenic analysis is designed to account for the effects of grain size and total organic matter. Results indicate that the flux of suspended sediment in the trunk channel in the upper watershed approaches 15 m3 over an average 48 hour fall storm to several times that amount during hurricanes with an average discharge of 500,000 m3 and average precipitation of 3 cm. The provenance of this sediment appears to be a mixed contribution from both overland and legacy sources in which the overland sources dominate the steeper headwater portions of the watershed and legacy sediments dominate in the lower reaches. These results are consistent with earlier estimates that relate annual suspended sediment flux to channel widening, a phenomena clearly documented in historic air photos.
