For eroding island, engineers' efforts start with models
March 25, 2013
NORFOLK, Va. (March 25, 2013) -- Waterman and residents on the tiny, sinking island of Tangier worry every time the winds blow through the fishing community at more than 30 miles per hour.
The island, located in the Chesapeake Bay just below the Maryland and Virginia border, is sinking and eroding away -- a dilemma that's expedited by churning storm waters.
"We take a pounding out here whenever a storm with 40, 50 or 60 mile-an-hour winds hit us," said James Eskridge, the mayor of Tangier and waterman. "We lose more shoreline."
But residents aren't the only ones keeping an eye on the winds. A team of engineers and researchers with the U.S. Army Corps of Engineers, Engineering Research and Development Center, Coastal Hydraulics Laboratory in Vicksburg, Miss., is gathering wind data.
Dave King, Ph.D., a research hydraulic engineer, is supervising the effort in Mississippi.
King said because the area is open to the Chesapeake Bay and the mouth of the Potomac -- up to the first major bend -- it's a 30 to 40 mile area that, if the wind is blowing in the right direction, can generate "significant" wave action.
The combination of wind and waves in the navigation channel and harbor has caused considerable damage during the recent storms.
"We've had crab shanties torn down, boats sunk," said Renee Tyler, Tangier's town manager. "In the past we have had people who have had to start all over because they lost everything, their boats, their shanties and their business."
Starting over includes obtaining material to rebuild the structure and then purchasing equipment: platforms for crab pots, storage tanks, cleaning tables and freezers for the bait.
The price tag is about $25,000-$30,000, Eskridge said.
The average income for a resident of Tangier is about $42,000 according to 2010 census data.
"For the watermen, it's a lot time and effort, and once of these storms go through, all you have left is the pilings," Ekridge said. "You have to rebuild, but the watermen are reluctant to do so until they know there is some sort of protection."
Back in Mississippi, Corps researchers are using wind, wave, turbidity data and more to understand the Tangier Federal Navigation Channel and harbor. The resulting computer model will help determine what type and size of jetty will protect the waterway and harbor from wave attack.
"The model will help us understand shoaling patterns in the channel -- and what we can expect when we put different types of structures in to knock down that wave energy," King said.
King said the work can be tedious, especially in the beginning, and the end product won't be a flashy computer generated 3-D graphic model, but more along the lines of numbers on a chart or graph.
While time to set-up varies, entering the data will take longer than running the actual model. King said for some models, it takes months to input the information.
According to Larry Ives, Norfolk District's technical team leader, the modeling work in Vicksburg is vital to determining which design provides the greatest level of protection, is cost effective and feasible from an engineering and environmental standpoint.
The final modeling analysis, expected in June, will give engineers with the Norfolk District a good set of design parameters to follow, maximizing the benefits of the new structure within the $3.6 million available to design and build it.
For the residents, movement forward on the project, which has been in the works since it was authorized under the Water Resources Development Act of 1996, is a long-awaited and needed sign.
"We've seen other communities near here that have disappeared," Eskridge said. "It's something we are trying to prevent."