Historical Shoreline Changes in Response to Environmental Conditions in West Delaware Bay
Historical Shoreline Changes in Response to Environmental Conditions in West Delaware Bay
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Date
1990
Authors
French, Gregory T.
Advisor
Leatherman, Stephen
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Abstract
This study quantified historical changes in the
coastline of the west shore of Delaware Bay. Shoreline
changes were measured through the compilation of
historical maps and photographs utilizing the Metric
Mapping technique. These changes were correlated with
various environmental conditions and with human
influences.
The results portray a 135 year pattern of overall
erosion, with long-term rates averaging -4.5 ftjyr,
which is considerably greater than the u.s. Atlantic
coast average. Coastal engineering (e.g., groins,
jetties and beach nourishment) were locally effective
in reducing erosion rates and in some cases promoting
limited accretion. Perhaps more importantly, there
were few associated negative effects alongshore
suggesting that various forms of coastal engineering
can be effective in a low-energy environment, even when
done in a somewhat unorganized fashion.
A correlation was found between erosion rates and
underlying Pleistocene morphology. Where pre-Holocene
sediments were exposed in the nearshore, erosion rates
were lower. However, erosion rates were substantially
higher along marshy shorelines.
This erosion is not continuous either spatially or
temporally, but instead is largely storm-driven.
Periods of relative quiescence corresponded with
lowered rates of average annual shoreline recession.
With the exception of the northernmost marshy areas,
severe erosion occurs along all shorelines, regardless
of morphology, in response to major coastal storms.