Unraveling the Mysteries of the Hudson River

New York’s Hudson River is famous for breathtaking scenery, majestic bridges, and a death-defying emergency plane landing. But for the U.S. Army Corps of Engineers (Corps), the most significant elements of the river lie at the bottom.

The Corps is responsible for maintaining all federal navigation channels throughout the U.S. and US territories. The Hudson Federal Navigation Channel is a high-traffic commerce thoroughfare, with more than 16 tons of cargo and nearly 900,000 cruise line passengers traversing the waterway annually. Each year, the Corps’ New York District conducts a hydrographic survey to monitor the condition of the channel, report any obstructions that can impede safe navigation, and calculate the volume of shoal matter to properly plan for future dredging. “It is necessary for the federal government to do all within its power to not impede the movement of goods through our ports, especially with post-Sandy influence on debris,” said Miguel Surage, who is with the Corps’ New York District.

McKim & Creed was charged with mapping 63 miles of the Hudson River Navigation Channel. We had performed the survey in years past, using single-beam sonar and running lines parallel to the channel along the centerline and both edges. In 2016, however, the District upped its technology requirements to “full bottom coverage,” aka, multibeam.

“’Full bottom coverage’ requires that the entire bottom be surveyed to the density that an object that is 1 cubic meter can be detected,” said David Jones, PLS, regional manager with McKim & Creed. The technology that provides that clarity, density and resolution is multibeam bathymetry, which collects data in such detail that you can identify the make and model of sunken cars and pinpoint the ribs on a shipwrecked vessel.

“What is very impressive about the [multibeam] data is how it is easy to interpret the sea floor from the data. All sea floor features are very apparent,” said Mr. Surage. “It’s the difference between walking in a room with a pinlight, which is like single-beam, and then turning on the lights with multibeam,” Mr. Jones added.

The data was collected between August and November, rough processed and QCed in the field, then post-processed in the office. Because the data was so clean, processing time was accelerated, said Martin Taylor, who both collected and processed data. “Roughly one day of acquisition equaled one day of processing.”

Unraveling the mystery of what is under the Hudson River intrigued Mr. Jones. Multiple artifacts were found in and near the channel, including several vessels and a 100-ft x 40-ft barge of some kind. “You’re surveying along and come up on a wreck or other structure, and you wonder, what is that? That’s the mystery, and as part of our job we determine what it is, and help keep the channel navigable to boot.”

(Photo to left) Damon Wolf (left) with ECHO 81, our equipment vendor, joins McKim & Creed hydrographic surveyors Martin Taylor, Heather Lewis and Jared Lambert aboard McKim & Creed’s survey vessel. McKim & Creed collected and processed multibeam data along 63 miles of the Hudson River. Among the many things the crew discovered on the river bottom were several small vessels and a large barge.
(Photo to right) McKim & Creed hydrographers Jared Lambert and Jeremy Starkey enjoyed the peacefulness of the river and the high bluffs of upstate New York.

Shown here is a wrecked ship below the surface of the Hudson River. The data is so clear that the individual struts on the hull are identifiable.

McKim & Creed used its 28-ft, Thomas Marine-built hydrographic survey vessel for this multibeam project.

Englishman Henry Hudson was searching for a quick passage to China in 1609 when he happened upon what is now the Hudson River. Long before that, Native Americans used the 315-mile river—known as Mahicantuck, or “river that flows two ways”—as a major travel route. Source: http://www.dec.ny.gov/lands/4923.html