Sonar reveals centuries of shipwrecks But N.Y. keeping maps secret

San Francisco Chronicle ^ | 12/20/2002 | Sonar reveals centuries of shipwrecks

[e_engineer]

Nyack, N.Y. -- Scientists mapping the bottom of the Hudson River with sonar say they have found nearly every single ship that ever foundered in the river over the past 400 years or more. Not just some of them, or most of them, but -- astonishingly -- all of them, except for a few that may have been disturbed by dredging.

The ghostly images provide a record of collisions and carelessness and storm-tossed fate -- most of it previously unrecorded and utterly unknown -- from the days of sail and steam through the diesel tugs and tankers on the river today. Altogether, more than 200 possible wrecks, spread out over 140 miles from the southern tip of Manhattan to Troy, have been identified.

But don't ask where the wrecks are. It's a state secret.

[e_engineer]

The article also reveals some very ancient walls were discovered on the bottom of the Hudson river:

The surveys have also turned up more mysterious structures, including a series of submerged walls more than 900 feet long that scientists say are clearly of human construction. They say the walls are probably at least 3,000 years old, because that was the last time the river's water levels were low enough to have allowed construction on dry land.

[CruisinAround]

Who are "they"? that profess to be experts, and by what evidence are the stuctures man made?

[e_engineer]

Good question. The article only mentioned unnamed "scientists". They probably used some type of side-scan sonar, which can give pretty detailed images of the riverbed.

I can understand them not releasing the locations of the boat wrecks, but the ancient walls are not likely to be looted.