USACE Field Research Facility
Field Research Facility
Coastal & Hydraulics Laboratory

Beach and Ocean

1. How far offshore is the Gulf Stream from the FRF?
50 miles offshore from Duck, 20-25 miles offshore of Hatteras.

2. Why is the water warm one day and cold another?
Wind is the biggest factor in water temperature. When the wind blows from the ocean towards the land, it blows water that has been warmed by the sun towards the beach. When the wind blows from the land towards the ocean, that warm water is push out to sea, and the cold water from underneath rises to take its place at the shore. The warm water is clear because its on the surface, while the cold water that was on the bottom is full of sediment and is a murky brown.

3. What is an undertow?
When a wave hits the beach, its force can often cause the unwary or young people to fall down. Once they have fallen, the wave will recede and pull them back into the water. When you are pulled into the water, simply stand up and walk back to shore. Undertow is a very weak current that draws excess water back into the deeper ocean. It will not pull you under and keep you there as is often misunderstood about undertow. Undertow is actually harmless to the individual. The myths attributed to undertow are stemmed from the realities of rip currents.

4. What is a rip current?
A rip current occurs when there is a build up of excess water in front of the sandbar. The water wants to flow downhill through the sandbar but it is blocked, building up pressure. The pressure is released through the point where the sand bar is weakest. This creates a hole in the sand bar where all of this excess water flows through at a very fast rate. Anything or anyone caught in the pull of the rip current will be pulled out past the sand bar until the pressure is alleviated.

5. What is the typical width of a rip current?
Approximately 50 ft wide, can be up to 90 ft wide and 3000 ft long. For more information on rip currents.

6. Why aren't there any shells on the beach?
That is not entirely true. We do not have a sheltered coastline and we are not a tropical beach. So our beaches do not have a wide variety of shells to choose from. We have a high energy coast line full of gravel that can break shells into smaller pieces. Storms and waves can bury shells deep in the sand where they will be ground into sand. There are clams, conch, whelk, and even oysters can be found on our beaches. The absence of shells though can also be attributed to collectors. Shells that wash up over the winter and have not already been buried by the middle of May are often picked clean from the beaches. Other collectibles that can be found on our beaches include sand dollars, star fish, and sea glass.

7. What is the difference between a sound and a bay?
A bay is essentially a curved inlet of the sea enclosed by a coastline such as the Chesapeake Bay. A sound is a broad channel between an island and the mainland, such as the Pamlico, Albemarle, and Currituck Sounds.

8. What is the difference between a sand bar and a shoal?
A sand bar is a raised deposition of sand, gravel, or other sediment by waves or currents. A shoal is the same deposition of sand, gravel, or sediment but also provides a hazard to the navigation of watercraft.

Hurricanes

9. What was the most recent storm to cause severe damage to the Outer Banks?
Hurricane Isabel - September 18, 2003

10. What is the most recent storm to over-wash the dunes?
Hurricane Isabel in 2003 caused waves to wash out parts of highway 12 all over the Outer Banks, and created a small series of inlets on Hatteras Island. It was the most powerful storm to hit the Outer Banks since the pier opened in 1977.

11. What storm caused the most damage to this region of the Outer Banks?
The Ash Wednesday storm of 1962 caused the most damage to the Northern Outer Banks specifically, but Hurricane Isabel caused 400 million dollars worth of damage. Most damage was centered around Cape Hatteras. Duck received little damage in the private sector, but the FRF's garage roof was torn off.

12. What is the largest wave recorded at the FRF?
The largest wave recorded by the facility was recorded offshore at 8.1 meters (26.6 ft) during hurricane Isabel, September 18, 2003. Click here for more pictures.

13. What are the highest winds recorded at the FRF?
Approximately 120 mph during a storm.

Plants and Animals

14. What kind of vegetation existed on the property when it was acquired?
Before the 1930s there was very little local plant life on the property. It was barren land that the Navy began to use as a bombing range because of its isolation. From 1972 to 1974 both the Navy and North Carolina State University planted sea oats and other scrub brush on the North end of the property. Some areal fertilization was done to advance the growth of these experimental plants, but was halted after additional unexpected plants began to spread. Scrub brush grew rapidly and is the dominant plant form on the property today.

15. What types of vines are present on the property?
There are four types of vines on the trails through the dunes:

  • Greenbriar- arrow head leaves, "zig-zag" stem, little thorns (see photo)
  • Fox Grape- develop grape clusters which birds eat, have large, flat leaves, similar to maple leaves
  • Virginia Creeper- five leaves in star pattern along vine, has berries
  • Poison Ivy- three leaves, oily, hairy stem

16. What types of animals live on the property?
A study done in 1975 identified over 13 different species living on the property. Foxes are the largest mammals that live permanently on site. Occasional Bald Eagles have been spotted on the property. A black bear was seen strolling through the gazebo a few years ago. Various types of snakes - black snakes, cottonmouth. Lots of birds- osprey, sea gulls, falcons, mocking birds, and pigeons. Other animals such as deer, snails, insects, and ghost crabs as well. Sea turtles beach themselves to lay eggs, and even an occasional seal will play around the pier.

17. Where do the horses in Corolla get drinking water?
Fresh water ponds in the dunes, they can drink from sound sometimes. Although the sound does connect to the ocean at Oregon Inlet, the sound in Corolla remains fresh and drinkable because of the many miles of distance between the two points.

18. What are all the jellyfish that wash up on the beach?
Moon jellies are certainly the most common, but several others occasionally make landing. Portuguese man-of-war can often be blown in with a strong storm from the South. Sea Nettle, Mushroom Jellies, and cabbage Head Jellies are also known to be off the coast and can be blown into shore. Lions Mane Jelly Fish are among the rarest to wash up. They can be as large as 8 feet across and have tentacles 100 feet long.

For more pictures and information on coastal wildlife Click Here.

The Pier

19. How long was the pier built to last?
50 years.

20. What is the soil composition on the property?
The deepest cores taken in the area indicate that the soil is composed of silty sands, clays, and gravels which extend down at least 20 m (70 ft). Any rocks would be found at least 7000 ft down since all the material found here is a result of relatively recent sedimentation (on the order of tens of thousands of years ago). An oil well from 1945 drilled to 10,000 feet in Cape Hatteras and found no sign of bed rock.

21. Do the pier pilings enter the bedrock?
No. As discussed in the previous question, the bedrock is far to deep beneath the soft sand. The pilings began as one inch thick hollow tubes. They were pounded 40 feet into the sand until they met resistance. They were then filled with cement all the way up. This created a solid platform for the pier to rest on. The pier has been so sturdy that since it was established in 1977 has not moved more than a centimeter.

22. What were the construction costs for the facility?
About 7.5 million dollars.

23. Why was the pier built?
The concept of a FRF was first proposed in 1963 by Rudolph Savage, Chief of Research Division of the Coastal Engineering Research Center (CERC). The FRF was to have 4 goals.

  • Provide a rigid platform from land, across the dunes, beach, and surf zone out to 6-m (20-ft) water depth from which waves, currents, water levels, and bottom elevations could be measured, especially during severe storms.
  • Serve as a permanent base of operations for physical and biological studies of the site, the adjacent sound and ocean region by the Corps of Engineers, other Federal agencies, universities, and private industry.
  • Provide the Corps of Engineers with field experience and data that would complement laboratory and analytical studies and provide a better understanding of the influence of field conditions on measurements and design practices.
  • Provide a field facility for evaluating new instrumentation.

24. How long is the pier?
The pier is 1840 feet from the dune.

25. When was Duck Road moved to its present location?
In the 1960s. All road North of the pier remained unpaved until the mid-1980s.

26. What are the white disks along the dunes?
They are used as reference points for the video cameras. Using them we can get the geometry of the image. This takes a horizontal image and makes it vertical, creating an aerial map of the beach.

27. What are the white poles in the ground along the dune?
They are used as reference points from the ocean. The CRAB lines them up to make sure that the spot measurements are taken from is consistent.

28. Has the CRAB ever tipped over?
In 1987 the CRAB tipped over in a trough on the south side of the pier. A Corps debris boat the "Snell" was used to pull it out and it was up and running in two days.

29. What are the wires hanging down the side of the pier?
Baylor gauges that measure wave height. They work by running a small voltage down the cables. Where the water shorts the wires, the computer measures this distance as wave height 4 times per second. There are several baylor gauges along the pier, which allows for the tracking of a wave as it approaches the beach.

30. How many gauges are deployed in the water around the pier?
Approximately 30-40 gauges are deployed at a given time.

31. What are the metal rods hanging from the automated rain gauge?
They are used to help measure precipitation by preventing wind from blowing snow and rain around the gauge.

32. What is it like to work at the pier?
A high school student once asked that to Field Research Facility Chief Bill Birkemeier through a series of emails. Click here to read a conversation with a marine scientist.

33. How many people work at the pier?
11 people make up the permanent staff at FRF. Their fields of expertise are varied but they are versatile. The permanent staff includes oceanographers, computer specialists, and technicians.

34. What has been discovered at the FRF?
The FRF has from the very beginning been heavily involved in measuring oceanic events, whether it be waves, wind, currents, tides, ect. But experiments using outside resources have always been encouraged. Duck-X in 1978 tested the accuracy of a satellite radar images using data already collected from the pier. A Shoreface Experiment (ASEX) was the first experiment to study how sediments moved along the bottom due to wave action and currents. Duck82 studied sandbar movement during large storms. This was the first study to reveal the importance of sandbar changes to beach changes and the incredible speed at which it can happen. Duck85 dealt again with sandbar movement and beach changes but served mainly as a precursor to SUPERDUCK. SUPERDUCK made the startling discovery of sheer waves, large fluctuations in what should have been a steady current. DELILAH in 1990 wanted to learn more about these sheer waves. They discovered that the fasted part of the current occurred in the shore side trough, not over the sandbar as was once thought. DUCK94 and SandyDuck in 1997 both used a wide array of measurement devices to map the ocean floor and the changes that it went through over a period starting in the calm summer months, followed by the turbulent oceans of early fall. Numerous smaller projects usually supported by the Army or Navy have covered a wide range of topics, including mine detection and countermeasures, radar detection of waves and currents, and dune and marsh vegetation studies. For an in-depth report on the discoveries and contributions that the FRF has made Click Here.

Glossary

Acoustic altimeter

Sonar device to measure distance to the bottom (erosion or deposition).

ADCP (some vendors use ADP)

Acoustic Doppler Current Profiler - measures currents through the water column with acoustic transponders.

ADV

Acoustic Doppler Velocimeter - measures currents a point in three axes.

Aerial Photography

The FRF had semi-annual aerial photographs made along the Outer Banks (details)

Air Temperature/Humidity

see "Humidity"

Anemometer

Skyvane Wind Sensor used until 2 Dec 2003. R. M. Young Wind Monitor model number 09101 currently in use.

Argus Video

Video system for making coastal measurements (morphology, shoreline position, waves, currents, ...).

Barometer

Measure atmospheric (barometric) pressure.

Bathymetry

The measurement of depths of water in oceans, seas, and lakes.

Baylor Wave Gauge

Surface piercing wave gauge under the pier.

Bipod

Instruments and frame mounted between two vertical pipes jetted into the bottom. Instruments may include current meters, pressure gauge, sonar altimeter, and ADCP.

CRAB

Coastal Research Amphibious Buggy - 35 foot vehicle used for surveys and instrument deployments.

CTD

Water Conductivity/Temperature/Depth

Currents

Defined as the direction the current is heading towards. See details of specific data set as to the coordinates and units.

Datum

The FRF uses the vertical reference defined by the NGVD29. Horizontal surveys are in NAD 83.

Dew Point

The temperature at which the air must be cooled at a constant pressure to become saturated. That is the temperature the air has to cool to reach 100% relative humidity

8m-array (aka Linear array)

An array of 15 pressure sensors in a nominal 8m depth used for high resolution directional wave measurements.

GPS

Global Positioning System - satellite survey system used (by many) to measure positions on the planet.

Gust

Highest wind speed in sampling interval averaged over 5 seconds.

Heat Index

Apparent air temperature felt by humans based on the "heating" effect of the humidity. Computed when the temperature exceeds 80 F and humidity is above 40%.

Humidity

The ratio of the actual amount of water vapour in the air to the amount it could hold when saturated expressed as a percentage OR the ratio of the actual vapour pressure to the saturation vapour pressure expressed as a percentage.

The amount of water vapour the air can hold increases with temperature. Relative humidity therefore decreases with increasing temperature if the actual amount of water vapour stays the same.


LARC

Lighter Amphibious Resupply Cargo - Amphibious vehicle for surveys and instrument deployments.

PAR

Photosynthetically Active Radiation

Rain data

(Explain Cumulative rain)

Relative humidity

see "Humidity"

Salinity

Expressed in practical salinity units (psu).

Secchi disk

Used to measure water clarity (visibility)

Significant Wave Height

Generally determined as the mean crest to trough height of the highest one third of the waves in a given time interval. The FRF uses a spectral technique to determine a "significant wave height", called Hmo. For more information, use the significant wave height link.

SIS

Sensor Insertion System - crane-like device for deploying instruments off the pier.

Sonar

Sound Navigation and Ranging

Sound Speed (SSP)

Sound speed measurements from the CTD are used to correct sonar bathymetry measurements.

SupOb

Daily Supplementary Observations- water characteristics, meterological conditions, wave and current conditions.

Survey Sled

An instrumented sled equipped with specific gauges and meters to measure the longshore and cross-shore components of the current.

Sustained Wind

Highest wind speed in sampling interval averaged over 1 minute.

Tides

Predicted tides and measured (NOAA) are available.

Time Zone

The FRF uses Eastern Standard Time (EST) which is five hours less than Universal Time (GMT or UTC).

Visibility (Air)

Clarity of the air as determined by visible distances from the end of the pier.

Visibility (Water)

Water clarity determined with a Secchi disk.

Water Temperature

SupObs & temp string for vertical profile...

Wave Frequency

wave frequency = 1/ wave period.

Wave Height/Period/Direction

At the FRF wave height is typically listed as significant wave height (Hmo). Period is the peak period of the energy spectrum, and direction is the direction waves are coming from (see specific data set for details on coordinate convention)

Wavelength

The horizontal distance between successive wave crests. It is also the wave velocity multiplied by the period.

Wave Number

The inverse of wavelength.

Waverider Buoy

Buoy to measure wave height, period, and direction (direction after 1998 at the FRF).

Wave Spectra (directional/non-directional)

8m array, waverider, surface gages, pressure, etc.

Wind Chill

Apparent air temperature felt by humans based on the "cooling" effect of the wind.

Wind Speed/Direction

Speeds may be represented in units of m/s or knots (see documentation with data set). Directions are the direction the wind is coming from relative to true north (TN), unless specified otherwise.

Zeiss

System that incorporates in one compact unit a first- order electronic theodolite, distance meter, microprocessor, rechargeable power supply, and an interchangeable solid state memory module. It uses a collimated infrared beam to measure distance and the electronic theodolite to measure both horizontal and vertical angles.