Document Type

Student Research Paper

Date

Spring 2022

Academic Department

Biology

Faculty Advisor(s)

Dr. David Bowne

Abstract

Suspended sediment, nitrogen, and phosphorus are a significant source of pollution in the Chesapeake Bay, and levels of these pollutants in the watershed’s streams and rivers are concerning. Traditional approaches to reducing sediment and nutrient loads have focused primarily on upland soil erosion, but often fail to include in-stream processes like bank erosion. It has recently been shown that in the North American Piedmont geographical region, historic sediment that accumulated behind milldams in the 18th and 19th centuries, referred to as legacy sediment, is an underestimated source of sediments in the Chesapeake Bay. Breached dams result in altered stream structures that exacerbate bank erosion and erosion of legacy sediment. In this study, I aimed to examine the relationship between historic milldam density in a watershed and the current water quality leaving the watershed. I expected to find positive correlations with watersheds with higher milldam densities having higher current levels of suspended sediment, total nitrogen, and total phosphorus. Watersheds were constructed using ArcMap software based on USGS stream gauge stations in Pennsylvania and Maryland in the Chesapeake Bay watershed. Milldam density for each of these watersheds was calculated as number of dams per hectare, and linear regression analyses were run for each of the water quality variables. No statistically significant results were found for the 14 studied watersheds. More research is needed to determine whether there is a relationship between historic milldam density and current water quality indicators.

Notes

Honors Senior Thesis; Honors in the Discipline

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