Island Land Loss in the Chesapeake Bay: A Quantitative and Process Analysis
Island Land Loss in the Chesapeake Bay: A Quantitative and Process Analysis
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Date
1992
Authors
Wray, Rachel Donham
Advisor
Leatherman, Stephen P.
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Abstract
The rates and processes of land loss were studied
for seven islands in the Chesapeake Bay: Barren,
Bloodsworth, Hooper, James, Poplar, Smith and South Marsh
Islands. Rates and patterns of land loss were quantified
for the years 1848 to 1987 with the Metric Mapping
technique which utilizes digitized data from historical
maps and vertical aerial photographs. Processes of land
loss were determined through field surveys and correlated
with environmental factors.
Two distinct island types were identified which
exhibited different, long-term patterns of land loss.
Small, upland islands, termed the Northern Group, showed
rapid land loss along the main stem of the Bay primarily
due to wave action driven by the predominant westerly
winds. Land loss appeared to accelerate during periods
of high storm frequency. The long-term averaged land
loss rate for Northern Group islands is 1.9 ha/yr. The
averaged erosion rate on the western side of the islands
is 4.9 m/yr, compared to 0.68 m/yr on the eastern side of
the islands.
In contrast, the large, marshy islands of the
Southern Group experienced uniform marsh edge erosion and
interior marsh degradation. The Southern Group islands
lost land at an averaged rate of 5. 6 ha/yr, with an
averaged rate of marsh edge erosion of 1.2 m/yr. Land
loss appeared to be weakly correlated to storm frequency.
Interior marsh loss was not quantified for this study,
however, so this study provides an underestimation of
total land loss of coastal wetlands.