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January 2014 Issue

USGS Innovation and Dedication To Meet Pressing Coastal Needs

By Suzette Kimball
Acting Director, U.S. Geological Survey
As I take my second turn as acting U.S. Geological Survey (USGS) director, I am gratified to see the continued energy, creativity and innovation USGS employees exercise, especially when conducting science in the difficult environments and harsh conditions that we have seen this past year. With an eye to meeting pressing societal issues, which are fundamental to the mission of the USGS—from mapping the nation to quantifying its natural resources, and forecasting its vulnerability to natural hazards'these scientists and technicians have a can-do approach. They are constantly building on and brainstorming how to use existing equipment in new ways, adapt off-the-shelf tools and software, and invent unique systems and pioneer into the future.

This innovation and dedication is very evident in the projects of the USGS, especially in its Coastal and Marine Geology Program, which maps the seafloor to characterize geologic processes, such as sediment transport and bottom stress, and assesses coastal changes following major storms, including hurricanes. These projects and some of the cutting-edge tools and approaches implemented are explored below.

Response to Hurricane Sandy: Acoustic Doppler System
Immediately before and in the days following Hurricane Sandy, USGS boots were on the ground across the coast. For example, at Fire Island, New York, scientists swiftly worked to document widespread dune erosion, overwash and inlet breaching caused by the storm. The USGS worked in collaboration with the National Park Service, the U.S. Fish and Wildlife Service and the U.S. Army Corps of Engineers to measure the extent of beach change and calculate the volume and direction of sediment movement.

The data showed that the shoreline had eroded back an average of 70 feet, which is the equivalent of 30 years of change at historic rates (2.0 to 2.5 feet per year) of erosion. Data further showed that overwashed dunes lost as much as 10 feet of elevation. The storm also cut a new inlet, which was hundreds of feet wide, through Fire Island that allowed sea water to pour into the estuary behind.

To help determine whether the breach would enlarge, stay open or naturally close, USGS field crews had to find new ways to map the morphology of the breach in three dimensions and measure tidal flows in its energetic, shallow waters. First, the USGS engaged with the U.S. Army Corps of Engineers to use its amphibious vessel called the LARC to collect high-resolution bathymetric data. The LARC is uniquely designed to allow surveying in the water, across shoals and even through the surf zone up to the base of the beach dunes.

Next, the USGS adapted an acoustic Doppler current profiler system (ADCP) to monitor fluctuating tidal flows by attaching it to a remotely operated vehicle. Using data from the modified ADCP, USGS staff helped direct the LARC team to locations where flow conditions met minimum standards. These rapid response data helped the National Park Service and other local authorities assess the areas of the coast that were most vulnerable to subsequent storms, such as a strong nor'easter that struck the coast only a week after Sandy.

Monitoring Sediment Movement: Free Ascending Tripod
While several USGS teams were responding to Hurricane Sandy in the Atlantic, others were working in the Pacific testing a new system to better understand how seafloor sediment moves and where it accumulates.

The USGS invented the new system known as a free-ascending tripod, or FAT. The tripod will improve understanding that can be applied to better siting of deep-sea cables, assessment of hazards associated with submarine landslides, and determining whether and where pollutants are likely to accumulate on the deep seafloor.

Oceanographic instruments are typically deployed and recovered using cables from research vessels, and while this is a proven process, it is quite cumbersome. Through this process, a coiled recovery line and buoy are acoustically released and rise up to the sea surface, and then the instrument is hauled aboard a ship. At water depths greater than about 650 feet, however, that method of recovery is not suitable due to the length of recovery line required.

The experimental FAT is less cumbersome and an advantageous step forward for scientific research. FAT has a stainless-steel frame that stands 6.5 feet tall with a 13-foot triangular base. FAT carries a suite of acoustic and optical instruments for measuring current velocity, temperature and sediment concentration in the bottom boundary layer. Many of the instruments make simultaneous measurements during descent, creating vertical profiles of the properties being measured. A high-definition camera system documents temporal changes in seafloor morphology and bioturbation.

To recover the tripod from the deep seafloor and permit unobstructed flow near the seabed, USGS developed a unique mechanism to initiate raising it from the seafloor to the surface. The tripod is fitted with buoyant material that lifts the entire tripod to the surface, as opposed to other systems that hoist the tripod with a recovery cable and winch. Instead of a traditional anchor, which disrupts movement of sediment and water near the instrument package, the legs of the tripod serve as the anchor, with foot pads composed of lead and stainless steel.

An acoustic signal engages an innovative release coupling that relaxes the tension system in the support legs and detaches the footpads. Then, the tripod rises using the buoyant properties of the orange syntactic foam surrounding the structure. Field crews can easily spot the bright orange tripod when it reaches the surface, allowing them to efficiently and quickly retrieve it.

During the next few months, this unique tripod will be deployed in the South China Sea to understand factors influencing sedimentation in targeted regions. This includes distribution of near-bottom ocean currents, turbidity currents and mechanisms that trigger them, and sources and pathways of bottom sediment.

Recognizing a Luminary in Science: Abby Sallenger
I would like to take a moment to recognize a USGS luminary, Asbury (Abby) Sallenger, who passed away about one year ago.

Abby encouraged creativity and innovation that has led to a better characterization of coastal change processes, the understanding of long-term patterns of beach accretion and erosion, and the development of models to forecast sediment movement along the nation's dynamic beaches. For more than two decades, USGS scientists have been following Abby's lead.

As younger generations of USGS scientists and others in the research community build upon his ideas, there will be a steady stream of new inventions as well as innovative adaptation of methods, tools and models to understand the ever-changing coastal and marine world.

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