My neighbor blacktopped his driveway and it is now now 6 inches higher. My basement is going to flood because of it. What can I do?
First, get some bids on what would be the best way to avoid or mitigate the flooding. Once you know how expensive the fix is, then you have a basis for discussion with your neighbor.
Hopefully, your neighbor will recognize his exposure here, and pay for the mitigation. Sometimes it helps to note that your insurance company would get involved with his if there were damage. If not, then a discussion with a local real estate attorney would be helpful. Sometimes a letter from an attorney can get a response.