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BEACH PROFILING PROJECT |
| THE
BIG PICTURE
Why
study Maine's Beaches?
SEDIMENT SUPPLY
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The sandy beaches in southern Maine are one of the state's primary tourist attractions, as well as important habitats for wildlife. Beaches are dynamic features, however, that respond to a variety of forcing mechanisms. Because of growing population and increase in development along the coast in the past several decades, it is necessary to study and comprehend changes that are occurring in these systems. It is generally believed that the quality of Maine's sand beaches are declining due to encroachment by over development and the rising level of the sea. The public does not notice that these important resources are slowly eroding, however, until property and buildings are at immediate risk. The current laws in Maine require removal of buildings that are destroyed by a storm, and one cannot erect new engineering structures to protect property. Therefore, the only options for property at risk are building relocation and beach nourishment. Numerous court cases and distrust between the local citizens and scientists/government regulators are the result of these strict laws needed to protect our beach resources.
In an attempt to create a more
congenial working relationship between the coastal citizens and government
regulators, the Maine/New Hampshire Sea Grant Program is funding a project
that involves collaboration between the groups. Trained volunteers
are currently making topographic profiles of 10 important barrier systems
in southern Maine. Each beach contains two-four profile transects
and the volunteers use the Emery Method of beach profiling. They
start from a surveyed monument and simultaneously collect the data on a
monthly basis. In addition, moored wave/current meters offshore are
collecting data. Changes in the topographic profiles are a result
of external forcing mechanisms, the volume of sand in the barrier system,
and the volume of sand available to the barriers. By combining this
data, it is possible to determine how individual beaches respond to a variety
of meteorological changes depending on their level of development and the
volume of sand contained in, or available to each beach.
Barriers are most common along
continental margins where micro-mesotidal ranges are dominant. Relative
sea-level change and sediment supply govern the formation of barriers.
In addition to these two factors, tidal wave regime and the regional geology
maintain the changing systems and are responsible for the barrier's physiographic
characteristics. The glaciated New England coast harbors more barrier
systems than the mid-Atlantic region, but the total barrier length is less
and the distribution more sporadic. Paraglacial coasts are defined
as those on or adjacent to formerly ice-covered terrain, where glacially
excavated land-forms or glaciogenic seidments have a recognizable influence
on the character and evolution of the coast and nearshore deposits.
The coast of Maine falls into this category, and it contains over 200 small
barrier systems.
Kelley (1987) divided Maine's coast into four coastal
compartments based on bedrock structure and geomorphology. Arcuate
embayments with intervening headlands characterized the Southwest compartment,
which extends from the Piscataqua River, New Hampshire, to Cape Elizabeth,
Maine. Meta-sedimentary rocks, punctuated by several plutonic bodies,
compose the bedrock. The embayed coast is a result of differential
weathering of rocks, underlying structural trends, and the glacial processes
that dominated the area in the past. Because of process-response
mechanisms, the Southwest coastal compartment contains a variety of barrier
systems.
The level of development varies for the beaches involved
in the project. Some are highly developed, while other have been
uninfluenced by humans. Before decisions can be made on beach management
practices and beach nourishment projects, it is necessary to understand
how the beach responds. A beach that is developed will likely respond
much differently than one that is undeveloped. Therefore, it is important
to monitor the changes on individaul beaches, rather than making assumption
from results on nearby beaches.
Development Status of Beaches Involved
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How
does the topographic profiling fit in?
| The profiles show how the beach
topography changes from month to month, and over the course of the year.
Using the maximum and minimum profiles, a volume of sand that either eroded
or accreted on the beach can be calculated. This volume is the active
volume of sediment, also known as the sweep zone, that moved over the year.
Although there may be more sediment available to the beach, only a certain
percentage is active. By comparing the volumes obtained from different
beaches, it is possible to determine if there is local variability and/or
significant differences between developed and non-developed beaches.
In addition to looking at volumes of sand, the topographic profiles will also be compared to the meteorological changes that occurred over the year. By coupling the profile results with recorded meteorological data, it is possible to determine how different beaches responded to varying wind, wave and tide conditions, as well as analyzing the changes induced by specific storm events. It will be beneficial to compare developed and non-developed beaches, as well as the location of the beach along the coast. |
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Website last updated January 21, 2001
Webmaster: Heather.Heinze@umit.maine.edu