Assessing Land Use Changes Using the Legacy Sediments in Shenandoah Valley, Virgina
Major: Environmental Geology
Dams have been used historically in Virginia to create hydroelectric power, for navigation, and to power mills. Although most have been removed in recent decades, in 1860 there were at least thirty operating mills and ten navigation dam structures along major waterways in Rockbridge County, VA. Emplacement of dams causes a decrease in stream velocity and buildup of legacy sediments behind the structure. These legacy sediments archive land use activities such as agriculture, timbering, and development since colonial times. By analyzing the legacy sediments and impounded waters, the land-use history of the area can be better understood.
From behind the removed dams, sediment was collected and analyzed using geochemical proxies. These proxies include carbon and nitrogen isotopes, trace metals such as manganese, lead, and iron, and the amount of total carbon. Geochemical proxies from two locations along the Maury River, Jordan’s Point and Polecat Hollow, show correlation with shifts in land plant species and historical land-use changes such as mining and industrialization. Overall, this study aims to explain how human impact through land-use changes can be cataloged within the legacy sediments and how those changes can affect sediment for hundreds of years after industrialization and the evolution of agriculture.