U.S. Geological Survey coastal erosion study is coming to Cape Point
A white metal monster rolls across the broad expanse of Cape Point, following a sandy road along southern Hatteras Island. Its giant wheels sink into the wet sand as it approaches the ocean, but it does not slow down. It heads straight into the surf, wheels churning the water, and soon it is in deep water. It does not sink, however. Its wheels no longer visible, it now floats like a boat as its engine propels it toward its destination.
The LARK, as it is called, is a 35-foot long amphibious vehicle owned by the U.S. Army Corps of Engineers. Its captain, Ray Townsend of Duck, is carrying U.S. Geological Survey divers and technicians from Woods Hole, Mass., to a buoy that bobs in the waves.
The buoy marks the spot where, anchored on the ocean floor, new state-of-the-art instrumentation measures and records wave action. The divers will soon suit up and go below the surface to check on the equipment. Bottle-nose dolphins dance around the vehicle as it reaches its destination.
The southern portion of Hatteras Island at Cape Point is the site of some intriguing studies this winter, trying to further scientific understanding of coastal processes and how they affect coastal areas, in particular the Outer Banks of North Carolina.
The study area includes12 sites for what are called the nearshore instruments, of which this is one. The sensors look up at the ocean surface from below, measuring currents, wave direction, height, and period (how close together the waves come in).
The project is a collaborative effort headed up by the USGS, in participation with the U.S. Army Corps of Engineers, North Carolina State University, the University of South Carolina, and Georgia Tech Savannah.
Its final goal will be to provide information that can be used for planning future coastal management strategies. It includes, along with the 12 nearshore instrument sites, two offshore instrument sites, a video camera situated in the Hatteras Lighthouse, and a site for the WERA radar. There will also be several beach surveys and a dye study.
The USGS chose Cape Hatteras as the site for this study because it is an extremely dynamic system, with strong currents and wave action and rapid erosion rates. The results of the study, however, will be relevant to other coastlines as well.
Sixty to 80 percent of the coastlines in this country are eroding, according to USGS geologist Robert Thieler, because of sea level rise and unsustainable development. With approximately $9 trillion invested in infrastructure and resources and with most of our major ports at sea level, the economic and social impacts of their loss could be immense. Understanding the processes that cause the erosion is important.
The study, which was ongoing for most of the month of February, is being supervised by USGS civil engineer and oceanographer John Warner of Woods Hole Institute.
Warner studied ocean processes in undergraduate and graduate school and researched sediment transfer in San Francisco Bay to earn his doctorate. He did mapping surveys at Hatteras last September to establish the depths he would be working in — depths that he says were changed considerably in November by the coastal storm, now called Nor’Ida. Warner returned to set up the equipment for this study up in late January, with the assistance of about 25 co-workers from the participating organizations.
On Feb. 4, the National Park Service sponsored a public meeting at the Avon Fire House so that Warner and Thieler could explain what the project was about, how long it would last, and what it would involve. The meeting was well attended, with an audience of more than 50 interested residents, mainly from Hatteras and Ocracoke islands. National Park Service ranger Laura Sturtz opened the meeting and introduced the speakers.
The main goals of the project, as explained by the scientists, are to improve the understanding of the processes which lead to coastal changes and of their interactions with geology, so we can improve the capability to predict coastal change and vulnerability, for emergency planning and more sustainable development.
The study, they said, will look at the interactions of shoreline, nearshore, and offshore sediment transport processes through the use geophysical surveys, oceanographic surveys, and predictive models. Dune erosion, overwash, island breaching, and threshold crossing will be among the activities studied.
Using a PowerPoint projection system, the speakers showed images of what lies beneath the islands, Pamlico Sound, and the ocean. It was fascinating to learn about this unseen but vitally important underwater landscape. Ancient river beds, substrate materials, and geologic features have a big effect on how currents flow, sediments are transported, and erosion occurs. Understanding more about these effects will help in predicting where a storm might cut an inlet or where houses might be most at risk of washing away. Other factors that affect how vulnerable particular coastal areas are include tidal range, wave height, and coastal slope.
One of the topics discussed was the concern about climate change and resultant sea level rise. Temperatures have been relatively stable for the last 10,000 years, making possible human expansion across most of the globe. With temperatures rising globally and glaciers melting, however, there will be more free water in the oceans.
Scientists are not able to say at what rate or how much sea level will rise, but projections based on computer models suggest a rise of from three to six feet in the next century. Looking at historical rates of relative sea level rise that corresponds to global and local tectonic processes (land motion such as uplift or subsidence) can help scientists make predictions. For example, Alaska’s coastline is, for geologic reasons, rising faster than sea level and thus will not be affected nearly as much as the mid-Atlantic shoreline.
Warner and Thieler want residents and visitors at Cape Hatteras to understand their project. Most of the sites are identified by signs. “Don’t be surprised if you see us or our equipment on the beaches,” the signs state, “and please have respect for our instruments.”
John Warner and his crew got a great chance to observe first hand what a bad Outer Banks storm could do to the island when, on Feb.10, a system with strong northwest winds flooded much of Hatteras Island and held up their work. Two days later, driving across the Cape and visiting the research sites, ocean overwash still stood in roads and campgrounds.
After watching the LARK and its diving crew get under way on a recent visit to the site, Warner explains a little about ocean dynamics. At Cape Hatteras, the waves can approach from opposite directions.
Underwater currents may move in different directions, and rip currents are common along this coast. Offshore of the tip of most capes, such as Cape Lookout, Cape Fear, and Cape Hatteras, is a big pile of sand, deposited there by the wave action. Diamond Shoals, lying off the coast from Cape Hatteras, is an example.
Why the sands stay in the shoals is something scientists would like to better understand and hope to learn from this project.
Hatteras and Ocracoke are not typical barrier islands, he adds, because of the 90-degree bend at Cape Point.
“Most barrier islands follow the coastline,” He says.” The ocean usually tries to straighten things out.”
Farther up the beach, near the spot where the Cape Hatteras Lighthouse used to stand, two groups of pipes protrude from the sand near a small trailer. This is the WERA Radar Site, set up by researchers from the University of South Carolina. Here high frequency radar signals are transmitted across 10 kilometers of ocean and along 10 kilometers of the shore, bouncing off the ocean surface and measuring surface currents and wave heights. The trailer houses the control units, where the signals are processed and data stored.
The next stop is the top of the Cape Hatteras Lighthouse, where Georgia Tech Savannah researchers monitor a video camera. The camera lens is directed at the ocean surf zone. It films and tracks breaking waves, transmitting the images to a computer inside the lighthouse, in order to better predict coastal erosion.
Offshore studies, contracted out to a group of researchers called the Woods Hole Group, use deep water instruments to measure currents and waves that have not yet interacted with the ocean bottom.
Warner discusses two other methods that are being used for the research.
The U.S. Army Corps of Engineers is conducting beach surveys, measuring the heights of dunes and offshore water depths (bathymetry). Using a truck equipped with lidar and X-band radar systems, they measure sand formations and determine ocean depths by measuring the height of the waves above.
A dye project, Warner explains, will involve shooting a bag of florescent green uranine dye into the surf with a giant slingshot. The dye is non-toxic, and the bag will biodegrade within minutes. He plans to use an airplane to view and photograph what happens to the dye once it enters the surf and hopes to learn about what he calls lateral mixing and longshore transport, measuring how fast the dye moves down the coast, how wide it spreads across the surf zone, and which direction it travels in when it reaches Cape Point.
An additional part of the project, not related to coastal change processes, is being done for the U.S. Navy. It involves microbial fuel cell technology — designing a battery which would use marine microbes in a chemical reaction to create an electric current.
The field work of the Cape Hatteras Coastal Study will be completed about the end of February, but analysis will take much longer, probably at least a year.
Meanwhile, Warner requests that if anyone sees anything that seems to be wrong with the instruments that it be reported to him at 508- 360-1631 or jcwarner@usgs.gov.
(For more information on the project, check the Web site at:
http://woodshole.er.usgs.gov/project-pages/cccp/index.html)
There will be many interesting pieces of equipment and plenty of activity on the Cape Hatteras National Seashore beach near Cape Point next month.
It will all be part of the U.S. Geological Survey’s ongoing research on Carolina Coastal Change Processes.
You can find out more about the project at a special National Park Service Know Your Parks citizen science program series presentation by the researchers on Thursday, Feb. 4, at 7 p.m. at the Avon Fire Station.
In a nutshell, this project is investigating the interactions of shoreline, nearshore, and offshore sediment transport processes driving coastal change in the Carolinas using geophysical surveys, oceanographic studies, and predictive models.
Equipment and scientists will begin working on the beach near Cape Point on Monday, Feb. 1, and work will continue through much of the month.
“Starting Feb.1, some unusual looking equipment will be on the beach between the former site of the Cape Hatteras lighthouse, south to access ramp 45,” according to a media release from USGS. “This equipment is part of a U.S. Geological Survey coastal erosion research study, under special use permit from the National Park Service. The goal of this study is to gain a better understanding of how to predict the hazards of beach erosion.”
Scientists will have equipment at about 17 sites offshore, in the surf zone, and on the beach. The equipment will be marked and signs will be posted on the beach throughout the month of February.
The presentation on Thursday will be by USGS scientists Dr. John Warner and Dr. Rob Thieler. The hour-long program is free and open to the public. A question-and-answer session will follow the talk.
Warner and Thieler will discuss the offshore mapping completed last fall and preview the fascinating scientific activities that will include sand dunes rigged with radar, a green dye study, a lighthouse camera, divers, and amphibious vehicles deploying sensors.
These instruments will measure the speed and direction of ocean currents, waves, and other forces acting on the beach, in the surf zone, and beyond. Cutting edge instruments have been developed specifically for this study, to measure forces during normal conditions and during storms.
The instruments, beach surveys, and offshore mapping will reveal many things about the sandy beaches of the seashore – how much sand there is, how fast it travels, where it comes from, and where it goes.
The goal of the research is to better understand, predict, and mitigate the hazards of beach erosion at Cape Hatteras.
The research study is being led by the USGS in Woods Hole, Mass., and is just one component of the much larger Carolina Coastal Change Project. The USGS, U.S. Army Corp of Engineers, along with the academic institutions of the University of South Carolina, North Carolina State University, and Georgia Tech Savannah, are collaborating on the project to investigate coastal processes, focusing on the Outer Banks of North Carolina.
For more information, check the Web site at:
http://woodshole.er.usgs.gov/project-pages/cccp/index.html
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