Alas, the nice slotted cap I put on the driveway drain can’t handle the amount of debris released by the trees next to the house and above the gutters. I’d removed the thumbscrew to simplify clearing the cap whenever I go for the mail, but that just accentuated the problem:
The backup must be over a foot of water at the end of the pipe; that fountain emerges from the 1/4 inch hole for the thumbscrew. Fortunately, the slope is large enough that the water (probably) isn’t backing up into the retaining wall footing drain.
When the pine trees toss their dead needles overboard, the cap plugs solid and, minus the screw, blows across the driveway:
It usually doesn’t roll very far, although I’ve retrieved it halfway to the street.
I still think the chipmunks will move in without a grate blocking the pipe, but I’m unsure how to proceed…