Phragmites is a common tall grassy invader of wetlands. Maybe that's it. Not sure about the cut bamboo-like weed from the second photo. Japanese Knotweed can look like bamboo at times so you might want to look that up also.

The photos are all of the same weed. It is not the Japanese Knotweed, but I found it on this website

http://www.nps.gov/plants/alien/pubs/midatlantic/phau.htm

It is known as the "common reed" - very labor intensive removal, including chemical, but did not say what type.

At least I found it, finally.

Here is a link that might be useful: Native Plant Society website

Check out this link.

Here is a link that might be useful: Phragmites (common reed)