This location is near a regional high school, baseball fields and a plethora of human activity. The snake beat a quick retreat to hide under the leaf litter, but was easily missed when walkers passed by on a regular basis.
So what kind of snake is it? Educated guess, based on the shape and habitat (near a stream in a ravine, fringed by woods), a northern water snake. Not poisonous.
So similar in appearance (at first) to a copperhead or a cottonmouth (not found in Connecticut), the snake can give a walker a start.
See more about how it lives and hunts www.uga.edu. Images of the species (eating a catfish) can be found at www.snakesandfrogs.com.