USGS DUNEX Operations on the Outer Banks

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Major support for DUNEX is provided by the U.S. Army Corps of Engineers. USGS activities are supported by the USGS Coastal and Marine Hazards and Resources Program. Academic partners are funded by the North Carolina Sea Grant and the National Science Foundation. Activities on Pea Island will be conducted under permits from the U.S. Fish & Wildlife Service, Pea Island National Wildlife Refuge and the National Park Service, Cape Hatteras National Seashore.

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Metal poles and equipment will be installed on the beach and in the surf zone out to 600 yards from the shore at Pea Island, just south of New Inlet, from September (after Labor Day) to mid-November. Installations may not be visible at all tides and conditions. These are EXTREMELY HAZARDOUS!! Please DO NOT SWIM, SURF, FISH, or BOAT between the signs on the beach (red zone below) and be cautious of currents that may cause you to drift into the hazardous area. 

The poles are 3” diameter and 15’ long, with about 5 feet extending above the seabed, to support the instruments that continuously measure wave heights, water levels, and currents using acoustics. 

Research proposed as part of DUNEX is separated into multiple interrelated research components, each with specific scientific and programmatic objectives and operational tasks. These include various forms of data collection and numerical modeling.  

Aerial Imagery of the Outer Banks.  Imagery from Duck, NC to Cape Lookout, NC has been collected, by airplane, every few months since August 2019, before and after storms. The goal is to evaluate the nature and magnitude of coastal change immediately after storms and during subsequent recovery. 

• Imagery is used to characterize the beach, dune, vegetation, and substrate.  
• Imagery is also used to produce digital elevation models (DEMs) and orthomosaic maps using structure from motion (SfM) techniques. 
• These maps are used to detect damage to property and infrastructure, changes in beach shape, including overwash and erosion, and changes in vegetation and landcover that affect natural habitats. 
• Beach profile data from DEMs will be assessed in XBeach and shoreline change assessed with the USGS models COAWST and CoSMoS. 

The Pea Island Experiment investigates the forces that cause flooding and coastal change: storm-driven waves, high water levels, and sand movement on an undeveloped barrier island. This involves intensive measurements of waves, currents, run-up, water levels, the seabed composition, sandbar migration, and sediment transport via the following: 

• Hourly to daily time series measurements of water levels and beach change using a stereo camera monitoring station. 
• Measure waves, currents, and sediment transport with offshore buoys, platform sensors, an array of sensors suspended in the surf zone, and a cross-shore array on the beach*. 
• Beach surveys to measure beach width, slope, and shape using GPS and imagery from a camera mounted on a tethered kite/balloon. 
• Bathymetric surveys of the nearshore using acoustic instruments mounted on an autonomous surf vehicles. 

A similar project will be conducted at the Field Research Station in Duck, NC to compare the same forces in a heavily modified residential area.  

*To withstand the power of the ocean during storms, these instruments are mounted on long steel pipes that are jetted into the seafloor. Once installed, up to 6ft of the pipe and attached instruments still protrude from the seafloor towards the sea surface and may stick out of the water on very low tides. These create an extreme hazard to those using the area – the danger zone is indicated by signs placed on the beach. For your own safety please avoid swimming and surfing in this area and be cautious of currents that may cause you to drift into the hazardous area.  

Geophysical and Topobathy Studies at the USACE Field Research Facility in Duck, NC will investigate how the geology and morphology of the shoreface respond to storms on a developed and partially armored barrier island. This includes pre-storm, post-storm, and recovery period data. 

• Collect seismic data to identify relationships between nearshore sandbar migration and sub-seafloor geology 
• Collection of topographic and bathymetric data to measure changes in the beach-dune and nearshore system 
• Collection of sediment cores to study grain size and sediment transport 

Numerical Models of waves, currents, water levels, and sediment transport, can fill in gaps in space or time in the observations and can be controlled to investigate specific oceanographic forces. Models are being developed and compared to measurements made at the USACE Field Research Facility and Pea Island. Insights into coastal processes gained from numerical modeling experiments expand our ability to forecast waves, water levels, and coastal change around the US. 

By combining the data from all aspects and locations of the DUNEX project, model outputs, maps, and historical data researchers will be able to highlight areas of high impact and evaluate changes over time. Analysis of these data will help expose the implications of storm-induced coastal change, specifically for humans and early successional species (e.g., piping plover, sea turtles).