Date of Award

12-2009

Document Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department

Environmental Sciences

First Advisor

Allen M. Gontz

Second Advisor

Curtis R. Olsen

Third Advisor

David E. Tenenbaum

Abstract

RISES conducted a shoreline change study in order to accurately map, quantify, and predict trends in shoreline evolution on Rainsford Island occurring from 1890-2008. It employed geographic information systems (GIS) and analytical statistical techniques to identify coastal hazard zones vulnerable to coastal erosion, rising sea-levels, and storm surges. The 11-acre Rainsford Island, located in Boston Harbor, Massachusetts, consists of two eroded drumlins connected by a low-lying spit. Settled by Europeans in 1636, the Island was later used as the Harbor’s main quarantine station. Previous archeological surveys have identified numerous historically sensitive sites dating to before the Revolutionary War period, including a large cemetery.

Multiple data sources were integrated within a GIS, including historical maps, aerial photographs, and Light Detection and Ranging (LIDAR) data. The United States Geological Survey’s (USGS) Digital Shoreline Analysis System (DSAS) was utilized to determine rate-of-change statistics and distances. A comparison analysis was carried out between datasets to determine the change in area above the high water line (HWL).

RISES used two proxies to delineate shoreline positions and one to delineate vegetated areas. The main shoreline indicator was the visually discernable high water line (HWL). A tidal datum/LIDAR derived mean high water (MHW) shoreline was also developed. Lastly, the visually discernable vegetation line was used to delineate vegetated areas.

The results show that 14% of the Island has been eroded during the study period with the largest losses coming between 1970 and 1992. There has been 60 m of accretion, at a rate of 0.83 m/y, within the West Cove. The spit connecting the two drumlins has migrated southeast by 17 m at a rate of 0.33 m/y resulting in erosion along its northern side and accretion along its southern side. The southeast beach on the northern drumlin eroded 43 m at a rate of 0.59 m/y. All other areas of the Island remained stable. Predictive modeling indicates that 26% of the Island would become inundated with 1-m of sea-level-rise including the area containing the cemetery. The northern beaches and the cemetery area on the southern drumlin have been identified as coastal hazard zones.

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