I think, generally, you (a homeowner) are responsible for the water that lands on your property. You have teh responsibilty to ensure that it flows out/off your property appropriately. This means that gutters would be needed if the water otherwise is causing famage to a neighbor. (but if you lived on a private lot and weren’t causing any problems for others, they wouldn’t necessarily be needed.)
Small claims court is the last step, but i’d try DCRA first, as suggested. Of course, you could mention it to the owner first too.