Yesterday the Town of Duck held a meeting to share the interim
report of the Erosion Mitigation and Shoreline Management Feasibility
Study. This study was created by Coastal Planning
and Engineering, Inc. that evaluated the shoreline changes along the
entire Town of Duck.
It also investigated the cause, extent and severity of the
area known as the “Hot Spot” located north of the research pier. The study also worked to develop an erosion
mitigation strategy for the “hot Spot” as well as developing a long term
shoreline management strategy for the whole town.
The process of this will be a two phase approach.
The first phase
focused on:
- Developing a comprehensive understanding of the coastal process.
- Projecting the shoreline change rates for 5, 10, 15, 30 and 50 Years.
The Second Phase will involve:
- Developing a short term and long term management alternatives to address erosion.
o
Costs for permitting
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Where to obtain the sand
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Cost of construction
Phase one included the shoreline change rates, the trends
and reversals of the shore, is the pier impacting the shoreline change and the
economic losses due to the shoreline change rates.
To research the shoreline change rates LiDAR data set from 1996 –
2011. LiDAR
(Light Detection and Ranging) is an optical remote sensing technology that
combines laser light and positioning measurements to provide highly accurate
digital elevation.
This data was
analyzed from 1 mile south of Duck through 1 mile north of Duck. 543 transects were grouped into 10 segments
that showed similar trends 1996 – 2011.
The results of the
data did show that south of the pier the shoreline was relatively stable, north
of the pier there are “hot spots” and in these areas erosion is occurring at a
rate of 5 to 8 feet a year.
The trends and
reversal evaluation showed a net northward sediment transport, but could not
establish a clear relationship between the wave data and shoreline changes
based on LiDAR data sets. Another thing
to note is they did not see significant differences in regards to average storm
conditions between 1996-1999 and 1999-2011.
There were also no major differences noted from 1980 to 1996 compared to
any other time.
The pier impacts were
evaluated by using an analytical method that evaluated cross-shore (Even) and
alongshore (ODD) shoreline changes due to the potential obstruction. The EVEN influence is storms impacting the
shoreline about the same up and down the coast of the pier.
The ODD influence is
how the pier may influence alongshore sediment transport which would cause an
unequal impact up and down the coast.
The ODD and EVEN will equal the total shoreline response.
Below is the Even Odd Analysis:
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Image was produced by Coastal Planning and
Engineering, Inc.
|
The final part of phase one was the
economic loss due to the shoreline change rates. The study developed a predicted dune toe
position for 5, 10, 15, 30 and 50 years.
If the town of Duck decides to not take any preventive measures in a 50
year time it will result in an estimated 150 million dollar total loss. The structure will be considered a total loss
when the dune toe intersects or becomes inland of a structure. This amount only accounts for the structure
of the property, not the loss of tourism, rebuilding or any other factors.
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Image was produced by Coastal Planning and
Engineering, Inc
|
Moving into Phase 2 now that the problem has been identified the Town
of Duck will need to determine what are the alternatives to help lessen erosion
damage to both public and private property.
The costs will need to be established and the length of time it will
take to move forward with these alternatives.
Another factor will be to consider the economic value, innovative
solutions and the benefits to the Town of Duck.
The next phase where the alternatives will be reviewed will likely
be scheduled for an October or November meeting. The date has not been set at this time. The Town of Duck will be releasing the PowerPoint
presentation from the town meeting on their website. You will be able to access the information
from this study at their website when it is released.
Special thanks to
Andy Garman Director of Community Development for answering my questions.
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