18 Coastal Change: Natural and Anthropogenic Process-Response Systems (Posters)

AN EXAMINATION OF PAST AND POTENTIAL FUTURE SEDIMENTARY IMPACTS SURROUNDING THE SACO RIVER JETTY SYSTEM, SACO BAY, ME, USA

Paper number: 18-3
Program: THEME SESSIONS
Time: 1:00 PM – 4:00 PM

Authors

Abstract

Saco Bay contains Maine's largest sandy beach system. Sediment accumulation and erosion within Saco Bay are greatly influenced by a paired jetty system at the mouth of the Saco River. Initially constructed in 1867 by the United States Army Corps of Engineers (USACOE), the jetty system was intended to stabilize the river inlet and to facilitate commercial navigation. Now 2032 m in length, the North Jetty is one of the largest along the US East Coast. Its enlargement was erroneously predicated on the belief that the beach system was glacially sourced and sand was moving into the estuary from beaches in the north, when in fact sand moves from the Saco River as a source towards beaches in the north. As a result, the adjacent beach, Camp Ellis, has undergone severe erosion. It has suffered the loss of 33 properties since 1968. The last beach in the system north of the jetty, Pine Point, has accumulated enough sediment to construct an additional 50 homes in the past 50 years.

Mandated by Section 111 of the Rivers and Harbors Act, the USACOE continues to have an active role in Saco Bay. Currently the USACOE is modeling potential alterations to the jetty system to be coupled with 375,000 yds3 of nourishment to Camp Ellis. Proposed modifications include a 900 ft long offshore breakwater, a triad of 200 ft breakwaters, T-head groins, and various combinations of breakwaters and jetty spurs. Each of these modifications has economical, political, and engineering strengths and weaknesses. We are currently examining pathways and processes of sediment movement within and adjacent to the jetties. Geophysical, drifter, current meter and coring data collected recently and over the past 20 years indicate that sedimentary pathways vary seasonally and meteorologically in Saco Bay and that potential permanent structures may disrupt these avenues of sediment transport.