RESERVOIR SEDIMENTATION BEHIND TWO 19-20TH CENTURY DAMS ON CEDAR SWAMP BROOK IN EASTERN CONNECTICUT: A PRELIMINARY EXAMINATION

Dams trap sediment in their upstream reservoirs that reflect erosion and sediment transport in their contributing watersheds. In the New England region, many man-made dams built for mills and other hydropower reasons in the 18th-early 20th century were in place while the region was experiencing widespread forest clearing for agricultural activities, likely leading to significant amounts of human-induced, legacy sedimentation within upstream reservoirs. In this study, we present results from sediment cores collected behind two dams built in the 19th century along Cedar Swamp Brook in eastern Connecticut. The upstream dam is stone and earthen, was built ~1810, and no longer has an upstream pond; the downstream dam along Bone Mill Road, was built a little later (~1850) and continues to dam Cedar Swamp Brook today with a 0.5-1.5 m deep pond upstream. Both dams were likely part of the same historic mill complex at the site. This sequential series of dams provide an ideal opportunity to study the storage and redistribution of reservoir sediment in eastern Connecticut. Loss on ignition (LOI) and X-Ray Fluorescence (XRF) analysis of the two sites has been completed and functions as a preliminary indicator of sedimentation changes. A bathymetry map of Cedar Swamp as well as GPR transects were used to determine coring locations and sediment thickness. Mercury concentration and 210Pb dates are being completed to further constrain sedimentation rates. Ongoing analysis will determine the volume of reservoir sediments and sedimentation rates using dates and geochemical constraints. We will compare sedimentation rates to other rates in the region, as well as sedimentation rates that existed in the Holocene prior to European settlement and widespread land clearing in the 18th-early 20th century.