Stretching from Norfolk, Virginia, to Miami, Florida, the Atlantic Intracoastal Waterway is an inland channel for recreational boaters and commercial shipping. The waterway is maintained by the U.S. Army Corps of Engineers (USACE). The mission of USACE is to “provide vital public engineering services in peace and war to strengthen our nation's security, energize the economy, and reduce risks from disasters.”

At Wilmington District headquarters in Wilmington, North Carolina, USACE surveys and maps the conditions of waterways in the coastal regions of North Carolina and south-central Virginia.

Todd Horton, chief of the waterways management section, says USACE boats, equipped with sophisticated sonar, cross over sections of the Atlantic Intracoastal Waterway every day. The district’s survey boat fleet consists of the Gillette, the Beaufort, and the Sanderson.

“They determine how deep the water is,” he says. “We do hydrographic surveys, which are water surveys, basically.”

A GPS signal determines the location of where the survey is conducted, and the sonar equipment records the depth of the waterway at that point. “They will collect all the soundings,” Horton says. “Whatever they survey that day, they send to us that night.”

The information becomes a new or updated data layer for online maps of the waterway. The maps are updated every 24 to 48 hours. The waterway maps help recreational boaters and commercial shippers avoid running aground or hitting obstacles.

Cartographer Adam Faircloth is one of the people who create the waterway maps. “Data comes to us in a lot of different formats,” he says. “My job is to take satellite imagery, hydro data and topographic land surveys to create maps.”

Horton says the sections of the waterway that connect to inlets change frequently. Even small changes to the depth or width of a channel can require different navigation from boats and ships.

“If you get a big storm, that can blow material into the waterway,” he says. “Anywhere it intersects our inlets, that’s pretty much the worst.”

Dredging

When the waterway’s channels become shallow because of sediment build-up, the U.S. Army Corps of Engineers sends a dredge boat to remove the material and make the channel deeper. The Wilmington District has the only shallow-water dredging fleet in the nation. This fleet includes the Currituck, the Merritt, and the Fry, which will soon be replaced by the Murden.

The Merritt and the Fry are sidecast dredges that pump the sediment onboard. Then, with a long, arm-like tool called a discharge pipe, the dredges cast the sediment about 45 meters (150 feet) from the channel. Both the Merritt and the Fry were Navy vessels initially built to pick up downed aircraft during World War II.

Roger Bullock, the Wilmington District’s chief of navigation, explains how the Currituck removes the sediment differently than the Merritt and the Fry. “The dredge in motion essentially vacuums material from the channel . . . transporting it to its hopper bin,” he says. “When full, it sails from the channel to a designated dumping site and the hull splits open, side-to-side, allowing the material to fall freely out of the bottom.”

North Carolina’s famous Outer Banks are constantly in motion, making dredging and managing the waterway difficult. One of the district’s greatest challenges, for instance, is to keep the Oregon Inlet channel deep enough for its constant stream of fishing boat traffic. Oregon Inlet is a body of water that connects Pamlico Sound to the Atlantic Ocean.

Bodie Island, the barrier island to the north of the inlet, is migrating south. As the island drifts, sediments gather in the channel.

“That’s the only access to the northeastern corner of North Carolina [by boat],” Horton says. “Lately, we’ve had to keep a [dredge] vessel there almost continuously.”

Another special vessel the U.S. Army Corps of Engineers uses in the district is the debris-removal vessel the Snell. The Snell has removed sunken boats and a plane from the district’s waterways.

During the late summer and fall months, the Wilmington area can be hit with hurricanes. Some of the hurricanes that have landed in the region include Hurricane Fran in 1996 and Hurricane Floyd in 1999. The Wilmington District works with the U.S. Coast Guard (USCG) when hurricanes strike.

“Typically, we are the first boats surveying depths in the shipping channels, then the ferry channels, and continue on into storm-impacted priorities,” Bullock says. The Coast Guard and the Corps inspect waterways for debris and missing navigational aids, such as lighthouses and buoys. “We present the results to the USCG and make recommendations for opening channels,” Bullock says.

Changing Needs of a Nation

The USACE Wilmington District notes that its section of waterway is used differently than when it first was completed in 1940. Then, the waterway was a major commercial route with ships and barges transporting goods throughout the southeast.

Today, rather than viewing a barge transporting goods, engineers are just as likely to see a family heading out to go fishing. “Commercial traffic is decreasing, because they [shipping businesses] are going to larger ships that can’t access the waterways,” Horton says. “Now it’s become more of a recreational area.”