I’ve been holding onto this shot of the C&O canal for a while. The depression in the ground running diagonally across the picture is the canal itself. What interested me when I saw this picture was the drainage ditch running through the canal. It didn’t make sense to me to have two giant holes in the sides of your canal. I quickly assumed that this ditch and the walkway covering it were built after the canal went out of service.
I wanted to know more about the extent to which alterations like this have been made, but I’ve found nothing. I’ll keep looking.