I'm sure it is probably a regional thing but, what region are we talking about?
In New Hampshire you cannot change the flow of water that will adversly impact your neighbor.
You cannot (for example) run your downspouts over to the property line.
You are limmited on how many yards of fill (100 cubic) you can place on your property without a site specific approval from the State.
Check with you local Inspection Department to see what is allowed.
If the water was running from your property on to his, you may have to build some type drainage system to catch the water.
© 2017 Renovate Your World LLC