Hi, Y'all -
Couldn't help but take a look at this old topic. I wrote a book called "Devastation on the Delaware: Stories and Images of the Deadly Flood of 1955." It was published in October 2005 and is the only documentary of this event, still the record-setting flood on the river. It contains a LOT of info about historic floods on the Delaware, so it may be of some use in your hunt, if you're still looking for the strongbox. You can get it online at
http://www.55flood.com.
I researched this topic for three years and found a lot of info sources during that time. Thought I'd share with you that the Monroe County Historical Society in E. Stroudsburg and also their public library there have awesome map collections with LOTS of old historic maps, which I used in my research. The local collection in the library is especially good, and I believe I remember some good stuff as well at the ESU library, too. They've definitely got an excellent microfiche collection of the old newspapers of the day. And if you contact the Barrett County Historical Society, there are a few old timers there who are just bonkers about railroad history and could probably tell you exactly where they think that box was buried. They meet at the old Cresco train depot building.
Here's a site from the Del. Water Gap Rec Area itself, where they share lots of RR info:
http://www.nps.gov/dewa/parknews/back-issues-2003.htm
Two other possibilities for info on this are the Canal and Railroad Museum in Easton (just one floor above the Crayola Factory in the same building on the square) -- TONS of RR history and photos there. And there's a good network of website devoted to the whole PA/NJ RR, track systems that got washed out in '55, including the whole Nay Aug tunnel, etc. I know there's a Garden State Central Club (don't be put off at name differences -- the '55 flood was the beginning of the end for many of the lines -- especially the Delaware, Lackawanna and Western -- and they later merged), and here's one I used myself:
http://hurricane.shohola.org/
I have to say, I don't remember reading about any major flood on the river between 1903 and 1942. The latter isn't a famous flood because it happened during WWII when the US didn't publicize any even that may have indicated to enemy powers that we were at all vulnerable. And then the next one after that was 1955.
For what it's worth, my first book was about the first century of statehood in Wisconsin, which has a long history of logging and trapping. I spoke with a number of historians who told me that people think stuff that goes into a river always gets washed away in flood, but surprisingly, that's mostly only true of stuff that floats. Things that are heavy tend to go rapidly to the bottom and to stay there, often within inches of where they first hit bottom. This is especially true of rivers with rocky bottoms, and especially in areas with rapids and riffles, because the flow of water around these rocks tends to drive stuff already at the bottom even further into the mud, or jams it up between other rocks.
Consequently, if you're brave and have a high tolerance for cold and a really good wetsuit, you can, to this day, still dive most of the rivers in Wisconsin and find items from the fur trade (circa 1700s right through about 1830-50, depending where you are). Most of these things lie among the rocks in higher-class rapids or directly below them, where canoes most often overturned. They're still bringing up old long rifles, strongboxes (with the wood still intact where the water stays cold), chains, traps, fire steels, trade beads, you name it.
I bring this up because A) I don't think there was a big enough flood between 1903 and 1955 to have washed that strongbox away, and B) even if the '55 flood DID chew it out of a bank, it wouldn't have gone that far before heading to the bottom. And I doubt it would have opened up unless something massive banged into it with a very sharp blow. And since everything else would have been moving along in the current with it, I don't think that's a likely scenario.
Oh, and BTW: I gave a talk just this past summer up at the Dingman's Ferry landing on this very subject, and the group arrived late. So, being a newb and having no idea I was doing anything wrong, I took out my Garrett Ace 100 and swung it around on a campsite while I waited. No one said anything to me, and I saw a ranger car, a park workman and the host ranger, and not one person said boo to me about it. I didn't realize until I was just reading here that I did a no-no. But just to say how I don't think anyone would say anything to you if you were to just nose around a bit... (and BTW, I only found pulltabs and a ball of foil - LOL. At least I had the common sense to fill my holes).
Good luck!
Mary in Bucks County