The background details:
-Located in Tulsa, Oklahoma.
-1/5th acre size lots
-Neighborhood built in 2000.
-Wife bought the house in 2015
I have a question about flooding that is occurring in my backyard. There is a very slight slope in the backyard that slopes from one side to another and from front to back(I have noted these in yellow but the slope is even across the whole yard. This slope carries on to yards around us. From what I can tell, the way the land was originally graded, the natural flow of water should be across the fence of the neighbor with the landscaping(noted in red) and either continue east across their yard. The landscaping is mounded, blocks some of the water flow and causes it to pool in the corner of our backyard inside the fence, noted in blue. The flooded area is usually 150 square feet and since our soil has lots of clay, it sits with standing water for days and days after a rain.
My wife bought the house in 2015, prior to us meeting, and the issue existed when she bought it. I looked though pictures on old listings and this landscaping in the neighbors yard existed when they bought the house in 2010. However, it wasn't in place when their house was originally built. We recently married and I want to get this taken care of.
Since the backyard slopes away from the road, we can't drain out to the road in front. My MIL was under the impression after speaking with the landscaping neighbor a year ago, that they would be ok with us hooking into their existing French drain system. Supposedly the neighbor with the landscaping had mentioned to my MIL or wife that the previous owners had complained about the standing water after a rain or something along those lines. The only way to do it completely on our property would be to have a sump pump installed over there to pump the water out to the road. Obviously this isn't my top choice since we would need electric run to the area, sump area set up, pump cost, and ongoing maintenance.
My wife contacted the neighbor wife earlier today about some upcoming fence work and mentioned that we would like to set up our French Drain system in conjunction with the fence work. The neighbor now says that from a legal and house resale perspective, she doesn't think they'll let us hook up to their French drain system and said we should do an electric sump pump system. I don't expect them to be neighborly about this issue and would anticipate them to tell us we're on our own.
Legal questions
From my basic understanding, you have to let water flow across your property and if you change the topography that causes the water to back up on upslope properties, you are responsible. This may be wrong but that was my impression.
-Is my understanding of the legal aspects of this correct?
-Legally, do they have to fix this rainwater drainage issue (either by allowing us to hook in to their drain system, removing the landscaping, or some other way) or are we on our own?
-Do any of the other factors(how long its been since my wife bought the house, landscaping existed prior to them owning the house) effect this at all?