I am currently at the tail end of some water issues. It starts from a spring fed pond plus various stormwater. The neighbors up hill from me have a lot of standing water due to their "flat" land and clay soil.
There is currently an above ground swale doing the job but not adequately. The neighbor dislikes the maintenance required and wants to put in a culvert pipe. They will also be piping in drainage from their driveway, roof, etc. to a settling basin with the ultimate goal to pipe all water underground. I believe their neighbor uphill from them will make their current basin larger to help when they grade their land to alleviate more standing water.
For us, the swale outlets across the edge or our yard where it turn gradually turns into the woods where there is a valley that it follows as a stream. The edge of the yard also grades a bit back into the yard so it doesn't take much to flood the yard before the water drains out.
I don't know what it was like before the neighbors started collecting a higher volume of water to send down but I'm sure it was worse. I'm afraid the change from above ground swale to culvert pipe is going to make things bad and curious what to do. After talking with zoning, it sounds like, assuming they don't change where the water outlets, they are allowed to do this.
I'm trying to approach this to allow them to solve the issues for them without negative impacting our own property. I see the following options:
Let them do as they plan and outlet the culvert pipe where the current swale does. Dig our own above ground swale that leads to the "valley" in the woods. Downside: if this swale overflows it will flood the yard. Upside: it is a gradual grade here and should help slow the water before reaching the valley / stream in the woods?
Let them do as they plan but have them outlet the culvert pipe down to the valley side. This will be out of the yard entirely. Downside: this valley side is a bit steep and more difficult to slow water. It will then take a ~45 degree turn down the valley. Possible erosion? Upside: very little change of flooding here.
Get them to change their mind or incorporate something to slow the water down that maintains the underground pipes? Will the size of their settling basins or design do anything to change the flow of and volume of water that comes to us?
The biggest fear I have is not just flooding the yard in option #1 but the stream in the woods continually flooding because there becomes too much water, running too fast that it can't sustain.
Any and all help appreciated. Thanks!