CHANGES
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CHANGES |
Barriers respond to a variety
of external forcing mechanisms including waves, wind, tides, storm events,
and currents. Current meters located in Saco Bay and Wells Embayment
showed the current direction and wave heights for a given time period in
February, 2000. We redeployed the current meters at the end of November
and will retrieve them in January, 2001. Cross-correlating these
measurments with meteorological data from the NOAA Portland Buoy 44007
allow us to observe how beach-profile changes correspond to specific weather
events.
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| FSI (Falmouth Scientific Inc.) current meter used in the deployment. The instrument attaches to a sturdy line one meter above the sea floor. | The boat in the foreground (RV Gulf Challenger) was used for deployment and retrieval. The boat belongs to the University of New Hampshire. |
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| Current meter deployment in February 2000. Water was freezing onto the railings instantly. | Current meter retieval in April, 2000. Conditions were much better! |
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The marine forecast for February, 2000, showed five
storm events on the 9th, 11th, 14th, 16th, and 19th. Using the buoy
data aids in confirming the storm events, while the wind direction characterized
the type of storm (ex. NE'rs). The wave height, wave period and wind
speed showed significant spikes during the storm times, indicating greater
intensity of the three variables.
The Portland Buoy is a 3-meter discus buoy located southeast of Portland, ME at 43o31'53" N 70o08'39" W
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Example of data obtained from
buoy records (http://www.noaa.gov). Wave period, wind speed and wind
direction are also useful when analyzing weather events.
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The significant wave height is calculated as the highest
one-third of all of the wave heights during a 20-minute sampling period.
The X axis is in days of the month (February), while the Y axis is the height in meters. |
WELLS EMBAYMENT
The current meter was located at a depth of 20.2 meters.
The mooring took place at 9:00 am on February 2, 2000. Starting on
the 3rd, the current meter recorded currents' speed and direction every
6 hours. At each 6 hour time, the current meter "turned on" and took
readings at 15 second intervals for a total of four minutes. These
four minute sampling intervals are referred to as a 'burst'. Therefore,
every 6 hours, 16 current measurements were determined in one burst.
For a general understanding of what was happening, the average of the 16
measurements were taken.
Average current velocity during the sampling interval. Each marker, which is 6 hours apart from the next marker, represents the velocity as a given time. In general, the spikes indicate times of high velocity currents and are most likely associated with storm events.
Average current velocity and current direction for every 6 hours during the sampling interval. Each individual line represents one burst. The negative vlues are read as an absolute value. They are used to indicate current direction.