I head out on a rising mid-tide with about 3 hours til peak. It is under 70F, calm, and overcast - all in all, a pleasant day for canoeing.
I head into the Nell's Island maze, after looking around to make sure that no one is watching - there are rewards for exploring, and I think that the maze counts as one. My first trips in here were at high tide. I had been convinced, because the island is a named feature on the maps, that Nell's Island was something like an "island". It is in fact, no more of an island than any other part of the marsh and the reason for potting it at all was probably because the navigable channel of the Housatonic is on the islands west side.

At high tide, I found a path of open water channels that would lead me from one end of the so-called island to the other. More recently, I started entering the maze during a rising mid tide. I got lost. The wider and straighter channels that I had used at high tide turned out to be shallow and not passable at mid tide. Instead of backing out, I tried the remaining narrow and very twisty channels, which turned out to be deeper and to link together into another route through the "island". It was a lot of fun.

The oldest maps of the area (in a usable scale for canoeing) date to ca 1850. That map is one of a series of town maps for New England. That map does show Nell's Island, but not the rest of the marsh. While trying to figure out what the marsh might have looked like, I had to consider what the purpose of that map was. It is quite accurate as far as roads and basic shorelines, and it has the houses and names of homeowners. It does not show property boundaries and topographic information is limited to hachures - a cartographic shading method to show hills. It seems that the main purpose of the map is to be an 1850 "telephone" book if you want - in 1850, if you wanted to talk to John Smith, you had to go find him.
The first government topographic maps are from about 1890. These detailed maps were produced by old fashioned on-the-ground surveying, a laborious process performed without the benefit of aerial views of any sort. Nell's Island appears on this first topo just as it appears in the 1850 town map...suspiciously so. If you study most any of the 1890's topos enough, you will find errors where surveyors just didn't go.
The next topo map of the marsh is 1951. Overlaying this map on the most modern maps shows very minor differences. The detail of the marsh is impressive. The 1951 map benefits from aerial surveys that were performed starting in the 1930's.
Having seen this jump in map accuracy and detail, I reviewed other river/marsh areas that I am familiar with (Chipuxet, Lieutenant, Mattebasset, Salmon, and East Rivers). In all cases, I found that the rivers on the 1890's topo maps were plotted incorrectly when passing through marshes, but lined up closely on the post-WWII maps, which all had aerial photo data to draw on. While rivers do shift channels, these changes didn't line up with standard river dynamics. The big change was the quality of the available data. Another thing to consider - all of the rivers couldn't all shift their channels between 1890 and 1950, and then not change significantly over the next 75 years.

There is a good reason for the errors. On the ground surveys require a landmark or an assistant who holds a survey pole at the point of interest. The surveyor can then sight and/or triangulate on that point and collect map data. With a river running through a marsh, it was, most likely, just too much work to send an assistant out into a marsh to accurately plot an area that could not be farmed, logged, or built on.
The reason the plotted river/marsh courses changed wasn't because of natural processes, it was because aerial photography allowed for an efficient method of plotting channels in a difficult to survey area.
I spotted two immature Yellow Crowned Night Herons - last year's fledglings, most likely. Also, I saw a pair of Mute Swans with 4 cygnets, 3 of which were white. A white cygnet is somewhat rare. Three in a brood must be very rare indeed. The Willets were more perturbed with my presence than they have been this year. That is their m.o. when nesting is going on. They flew around when I was near and made lots of noise so that everything in the marsh knew I was there.