Lab 7 Coastal Hazards 2023
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Binghamton University *
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Geology
Date
Dec 6, 2023
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Geol. 116
Fall 2023
Lab 7:
Coastal Hazards
You’re the vice president and senior principal for insurance company Denyallclaims in their San
Mateo, California, office. You were able to buy a really nice house in Moss Beach, across the
mountains on the coast, back before real estate prices went completely crazy in the San Francisco
Bay Area. But the company wants to transfer you to their suburban New York office in
Westhampton, Long Island. You’re really torn on this, because, despite the fact that you grew up
in New York, you’ve become very comfortable with the California lifestyle, especially your
house overlooking the ocean. So you’d like to be able to live on the coast if you do move to
Long Island. After careful review of the value of your Bay Area house (Zillow lists it at $4.1
million) and comparison with similar prices on Long Island, you’ve identified the community of
Westhampton Dunes as an option were you to move. But being the wise insurance executive that
you are, you want to further explore the risks associated with living on the south shore of Long
Island, particularly in this location, compared to your current West Coast abode.
You’ve decided to supplement what you can learn about the science and policy issues at
Westhampton Dunes with analysis of information about erosion and deposition along the south
shore of Long Island—and compare what’s been happening there with what has been occurring
at the town you currently live in, Moss Beach California. You find particularly useful
information from NOAA (the National Oceanographic and Atmospheric Administration at
noaa.gov), the New York Times, and other sources. And you learn there have been significant
issues at Westhampton Dunes, as well as where you live in Mass Beach.
Westhampton Dunes
Your goal is to identify how stable the Westhampton Dunes location is.
a.
How do coastal processes work here—role of longshore transport, large storms, extent of
beach, etc.? Note the first of the accompanying photos, which shows the effects of groins
at Westhampton Beach, which is immediately east of Westhampton Dunes.
b.
You’ve discovered a major event that occurred in the early 1990s: the island was
breached, and the breach was closed and refilled. You’ll find lots of information about it
online. What happened, and why? Examine the photos on the following pages; note
especially the relationship between the groins and the breach. Among the sources of
information:
https://seagrant.sunysb.edu/cprocesses/pdfs/LIDynamicSouthShore.pdf
(hint: focus on descriptions of the 1992 opening of Little Pikes Inlet/Westhampton).
New
York Times articles from August 27 and December 23, 1993 (see below)
.
The text on page 5 provides additional information. The New York Times article from
2003 provides an excellent update.
c.
What mitigating measures have been taken since this event?
How effective were they?
Answer this by first examining the impacts of Hurricane Sandy in 2012. Using Google
Earth and the history function, go to Westhampton Dunes and examine changes in the
coastline that occurred in 2012 by comparing images before and after the storm; use
Dune Road (county route 89) as a constant marker and measure the distance from the
road to the beach front.
The history of interventions since 1992 is briefly summarized in
this short report
from the
Army Corps of Engineers.
d.
What is the current situation in Westhampton Dunes? How has the beach changed as a
result of the groin system and recovery efforts? Look at recent images in Google Earth
and summarize the differences between the coastline in 2013, 2016, 2019, and 2021.
e.
Is this a good place to live, in terms of the potential for future events like the one you’ve
learned about? Explain your answer with information about the recovery of the area as
well as the risk for future events (such as the potential for storms to damage the area).
Moss Beach, California
a.
Time to look at your current location in California to get a better idea about the stability
of this coastline.
Your house at 201 Nevada Ave., Moss Beach, has a spectacular ocean
view. But you are well aware of the issues along this coast. Your house has been
protected by the large boulder accumulation that a previous owner emplaced to harden
the base of the cliff, but cliff erosion has continued immediately north and south of your
house. Use Google Earth and the history and path functions to estimate the amount of
coastal erosion around your house.
a.
First establish a “baseline” along the coast using the 1993 photo. You should be
able to mark the coastline (specifically, the crest of the coastal bluff), although the
image isn’t sharp.
b.
Mark the edge of the coastal bluff in May 2022. Describe the changes. Then
measure the amount of retreat (i.e. distance between the two lines) at 2 points, one
just north of your house and another just to the south.
c.
How rapid has cliff retreat been? To what extent is it greater or lesser in the
developed area north of your house versus the undeveloped area south of your
house?
b.
You’ll find relevant information about cliff erosion and stabilization in the Moss Beach in
the report available
here
; the images at the end of this document show the situation at
your house, with additional photos on p. 8-10 of the original document. What has been
the effect of the armoring in front of your house?
Putting It All Together
Finally, which site is a safer location to live—Moss Beach or Westhampton Dunes?
Justify your
answer in terms of what you’ve learned. Your report should be brief, no more than a few pages.
Include the measurements you made for Westhampton Dunes before and after Sandy, as well as a
screen shot of your lines in Google Earth and the measurements from Moss Beach. Even though
we’re asking a number of questions, you should be able to summarize everything in 2-3 pages of
text.
New York Times, August 27, 1993
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New York Times, Dec. 23,
1993
The Westhampton Beach groin field after initial construction
From:
Modeling long-term beach change under interacting longshore and cross-shore processes, by
Hans
Hanson,
Magnus Larson
,
and
Nicholas C. Kraus, 2011; Coastal Engineering Proceedings, no. 32, 11 p.
Evaluation of Groin Shortening
There are presently 16 groins at Westhampton Beach. The first eleven and easternmost (up-drift) groins were
constructed over 1965-1966 in response to breaching during the March 1962 northeaster.
Four additional groins
were constructed to the west during 1969-1970. The rubble stone groins in this field of 15 structures were
nominally 146 m long, tapering to the sea bottom and having spacing of approximately 365 m. Kraus and
Batten (2006) provide the most recent summary of groin configuration and functioning at Westhampton Beach.
The original groins functioned as intended (Nersesian et al., 1992) in protecting a once-vulnerable 5-km long
segment of barrier beach that had experienced breaching during the September 1938 Great New England
Hurricane, a 1958 storm, and the March 1962 northeaster. Although the ten groin compartments of the eleven
original groins were not filled during initial construction, natural longshore transport eventually accomplished
this. Over the years onshore-directed wind-blown sand has created a high and broad dune that is fronted by a
wide berm. Beach fill accompanied construction of Groins 12-15. In December 1992, a northeaster opened two
inlets (called Pikes Inlet and Little Pikes Inlet) directly west of the groin field. Pikes Inlet, located most
westward, gradually shoaled and was readily closed manually (Bocamazo and Grosskopf, 1999), but Little
Pikes Inlet enlarged in the eroding down-drift area directly west of Groin 15. In 1993, the U.S. Army Engineer
District, New York (NYD) closed the breach by hydraulic fill placement. In 1996-1997, a tapered groin
transition to the west was created by shortening Groins 14 and 15 and adding a short groin (called Groin 14A)
between them. The groin tapering together with beach fill has been successful, and the planned renourishment
of 3 years has been extended to 4 years.
Initial breaches, Westhampton Dunes.
Full extent of Little Pikes Inlet breach, 1992
Pikes Inlet breach
Filling in Little Pikes Inlet Breach.
Note
step-back in beach west of groin (in foreground)
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