4th Annual Maine Coast Natural History Seminar

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Maine Beaches and the Processes that Shape Them
4th Annual Maine Coast Natural History
Seminar June 5, 2004 Peter Slovinsky, Coastal
Geologist Department of Conservation Maine
Geological Survey
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Maines Diverse Shoreline
Wheres Waldo???
From rocky shorelines
to highly developed long sandy beaches.
to undeveloped pocket beaches.
Sandy beaches only comprise 2 of the Maine
coastline! About 70 miles! Beaches and dunes are
a VALUABLE RESOURCE.
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Maine Beaches Major Factors on Morphology

• Underlying Geology/Sediment Supply
• Sea Level Rise
• Waves, Currents, Tides, Wind
• Shoreline Stabilization/Development
• Recreational Usage Colonial Ordinance

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Underlying Geology
From Kelley (1987)
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Underlying Geology

• Beaches are limited 2 of coast
• Only 8 of nearshore is considered beach
  quality sand
• Most are pocket beaches or enclosed littoral
  cells (bound by headlands)
• Most have limited sand supply
• Beach shapes heavily influenced by the
  underlying geology

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Sea Level Change The Last 13,000 Yrs
The curve shows the fall and rise in the ocean
over the last 13,000 years. In the last 3,000
years sea level has been relatively stable (a
stillstand). From Dickson (1999) and based on
Barnhardt (1994) and Belknap et al., (1987).
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Shoreline response to Sea Level Change
Map showing the inland-most shoreline about
14,000 years ago, based on marine deltas and
shelly marine sediment. The offshore shoreline
position was about 11,000 years ago and defined
by sediments in cores, radiocarbon age dates, and
geophysical surveys of submerged strata.
MGS/UMaine graphic based on Barnhardt (1994).
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Sea Level at Portland
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Intergovernmental Panel on Climate Change Sea
Level Forecast
Source IPCC Technical Summary of Working Group
I Report, Fig. 24, p. 74.
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Summary of Sea Level Changes
13,000 to 11,000 years ago sea level fell 400
feet (20 ft/century). 11,000 years ago sea level
was at its lowest, 175 feet below present. 10,000
years ago to present sea level has risen 175
feet. 5,000 years ago sea level was 13 feet below
present. 3,000 years ago sea level was 6 feet
below present. 3,000 years ago the rate of
sea-level rise slowed to 0.2 ft/century. Since
1912 sea level has risen at a rate of 0.6
ft/century. The current rate of sea-level rise
is the fastest in the last 3000 years.
Source IPCC Technical Summary of Working Group
I Report, Fig. 24, p. 74.
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Waves, Currents, Tides, and Wind
These are the everyday forces that move sand
and cobble, building beaches and eroding
them. The majority of beach response in Maine is
due to waves in conjunction with currents and
tides.
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Processes in response to storm waves
Frontal dune ridge in Cape Elizabeth. About half
of the ridge was eroded and subsequently rebuilt
with American beach grass and sand. MGS File
Photo by S. M. Dickson, 1986.
US Army Corps of Engineers (1984)
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Seasonal Beach Change
June 2001
Ogunquit Beach Profile 2
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Dune Scarp Formation
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Frontal Dune Overwash
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Signs of Dune Migration
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Shoreline Stabilization and Development
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Popham Beach Property Damage
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Recommended Development Strategy
Development located landward of a natural frontal
dune ridge
Back dune development behind a wide frontal dune
ridge and elevated on posts in Wells. MGS File
Photo by S. M. Dickson, 1986.
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So where is the worst beach erosion in Maine?
Camp Ellis Beach, Saco
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Saco Bay
From Kelley (1987)
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Saco Bay Sand Budget
About 4,000,000 cy of beach sand moved north
(1859-1955), from the vicinity the Saco River
jetty to the Scarborough River tidal inlet. This
is about 3x the pre-jetty transport rate and 3x
the sand resupply rate of the river. From Kelley
et al., 1995.