What is this bush?

These pink flowers caught my attention. They are on  a woody bush in a gulch behind the towpath. I have not seen this bush anywhere else. There are a lot less leaves than there are flowers, but one of the few in focus, to the far right, gives you an idea of what they look like. I've gone through my book, but have no idea what this is.
     I am very tired. It's catching up with me now. I assume things will get worse before they get better. My mood has been low as well, though a friendly fruit fly cheered me up a moment ago by landing on my shirt twice. Maybe it liked the colour? (Navy blue.)