Hi Alfred. I can't help with the ID, but I really like this image with the raised head and view of the throat. Looks like this guy is on the hunt. The shallow DOF really makes the snake stand out from its surroundings.
It looks like a Northern Water Snake. They're very easy to approach within a few inches, but they can be quite aggressive if you need to interact with one to do something like move it off of a road.
Most snakes are great swimmers, but it's very cool to watch one of these guys working the bed of a fast moving stream. The way they hold their bodies against the rocks is amazing. Definitely something I'd like to photograph with an underwater housing.
Alfred,
You could've gotten a closer, more intimate picture by using your new 1-400L and laying on the ground with him. The chances of him charging you are virtually nil and as noted above, he's non-venomous ! :)
I like the barely visible body in the BG and the way the flowers provide some cover for him.
Probably a harmless water snake. Can't tell much from the position.. One thing you might remember about snakes in the U.S., if the snake has a round eye such as this one, it is non-poisonous, except for the Coral snake which also has a round pupil. With a Coral Snake just remember, in regards to the snakes bands that "Red and Yellow kill a fella, Red and Black friend of Jack".. If the snake has an eliptical pupil, like a cat, it is poisonous.