Is this, a development, in which there are community rules? ie: like in a subdivision or planned community?
Or is it just individual properties and individual owners on each lot?
Especially it it is a planned community/residential development... then there would be Homeowner Owner's Association rules, etc. too.
And this should address, EACH properties, drainage plans. As well as the city's codes.
Your property slopes downward. Into a swale type topography.
All this time, drainage was going into the next property. So no "complaints" about your drainage, was addressed before.
Now, it has.
Someone is going to develop that lot.
Per residential developments, EACH property owner is responsible for having approved drainage, per the HOA's guidelines. If not, then the homeowner, must do it. But in residential developments, even things like drainage and its flow-plan between properties, must be approved, and/or permitted and up to code. Formally. If a homeowner is negligent in even having proper drainage, then they must, put one in.
Our neighbor, once complained that our drainage/rain flow was going into his, yard. Sure, we saw it. BUT the thing is, WE DO HAVE, proper drainage in OUR individual property AND it was approved by the Association's building Consultants and it was, permitted and met code. Our own blueprints for our drainage plan (yes, we had to have this), is correct and it was done, correctly. The problem with the neighbor, and our so called drainage going into his property, was HIS problem. Because, HE DID NOT HAVE, proper drainage in his lot. Per requirements. And, our entire residential development, HAS a drainage plan per each property and the flow of water. And we are on, a hill.
And one property should not be, flooding another property.
So if you do not even have, proper drainage for YOUR property, then you do, have to correct it.
There are codes and building plans etc. and laws.
And, he would have to also have, proper drainage plans for his property too. It is a domino effect.
And you cannot just drain your stuff into someone elses property.
What if you were him?
And being that there is a whole slew of new homes being built there in these conditions, then this drainage problem will only increase.
Then, the entire development, will have big problems.
Just due to flooding or improper drainage etc. it can affect, the whole stability of a person's lot. And can make the ground shift. And then that creates big problems, on the structure that is built, on it. To say the least.
Eventually, as more homes are built there, there will be tons of water/drainage problems. Not only for you or your neighbors.