Geomorphic Identification and Verification of Recent Sedimentation Patterns in the Woonasquatucket River, North Providence, Rhode Island

摘要

The Woonasquatucket River in North Providence, RI, is a postglacial river flowing approximately 18 miles from its headwaters in North Smithfield, RI, to Providence, RI, where it joins the Moshassuck River and enters the Providence River. In 1776, a powder mill was constructed along the river to support the Colonies efforts in the American Revolutionary War. The powder mill exploded in 1779, sending tons of gunpowder into the river. Subsequently, with the onset of the American Industrial Revolution in the early 1800s, the river also proved an ideal setting for textile mills. Because the mills operated machinery by waterpower, the river was directed into raceways that flowed through the mills. Dams were strategically placed on the river to aid in the diversion. Mill ponds that formed in response to the obstruction substantially altered sedimentation patterns and depositional features. This research studies a section of the Woonasquatucket River in North Providence to assess the impact of these developments on the sediment regime. By using 210Pb and 137Cs, accepted methods of radioisotope dating used primarily in lacustrine and marine environments, a geochronology of sedimentation is established. However, because the mills predate the validity of these methods (approximately 150 years before present), other sediment dating techniques are needed to establish a geochronology of events prior to mill construction. Elemental sulfur and potassium nitrate, components of gunpowder, were analyzed in the sediment to determine a historic timeline prior to the nineteenth century. Although soils at the site of the powder mill contain unusually high levels of sulfur, samples taken in areas away from the effects of the powder mill explosion also reveal high elemental sulfur levels.