Date of Award

12-2001

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Geological Sciences

Advisor

Joseph T. Kelley

Second Committee Member

Daniel F. Belknap

Third Committee Member

Stephen M. Dickson

Abstract

Although sand beaches in southern Maine comprise only a small segment of the coastline, they are economically important to the state. From September 1999-March 2001, volunteers made monthly topographic profiles along nine beaches in southern Maine to monitor changes. The volunteers used the Emery Method of beach profiling to take simultaneous measurements at spring low tide. The beaches are significantly different with respect to physiography, incident wave energy and direction, available sediment supply and extent of development. An average of the profiles for each category demonstrates that the undeveloped beaches experienced regular seasonal fluctuations and a consistent berm elevation from one hill to the next. The moderately and developed beaches also showed seasonal fluctuations, but the berm during the &I1 2000 was close to 0.5 m higher than the berm in fkll1999, a response that was not observed on the undeveloped beaches. Weather, particularly storms, are one of the most important controls on the cycle of erosion and accretion. Current meters placed in shoreface locations of Saco Bay and Wells Embayment, Maine, recorded bottom currents during the winter months of 2000 and 2001. The current meters documented three unique types of storms: frontal passages, southwest storms, and northeast storms. In general, frontal passages and southwest storms were responsible for bringing sediment towards the shore, while northeast storms resulted in a net movement of sediment away from the beach. A northeast storm on March 5-6,2001, resulted in currents in excess of one mlsec and wave heights that reached six meters. The storm persisted over 10 high tides and caused coastal flooding and damage to property. Topographic profiles made before and after the storm demonstrate that developed beaches experienced a loss of sediment during the storm while sediment was redistributed along the profile on moderately developed and undeveloped beaches. Two months after the storm, the profiles along the developed beaches had not reached their pre-storm elevation. In comparison, the moderately developed and undeveloped beaches reached and exceeded their pre-storm elevation and began to show berm buildup characteristic of the summer months. The amount of sediment available to the system was another factor that played a role in the changes observed along the profiles. The expected high sand volumes in the summer and low volumes in the winter were generally not observed along any of the barriers. Eight out of the nine beaches showed a net gain in the active volume of sediment during the sampling interval. Results from the past year and a half suggest that profiling efforts need to continue into the future to minimize the effects of seasonal and other short-term changes and to determine whether the beaches are in a stable state. It is probable that the barriers are currently in equilibrium with human-induced alterations and a significant storm event is necessary to cause extreme erosion and movement of the shoreline.

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