Pond Dam problem

Ok so we have one low spot on the property. I'm enclosing an aerial view. I'd like to do a pond there. the problem is the dam. Filling out the paperwork for the permit I'm just stumped. How do I stop this from being catastrophic when it over fills? It drains off of my property, across a road and onto the farm field. You can see in the shot that the road there collects water already.

My husband has suggested doing stone on one part of the dam to allow leakage. I've suggested having the water pumped up higher onto our property. Anyone have any good tips for me?

Water flows off your property now. The land you would use for a pond will only absorb so much water.
The key to design is how much water would your property absorb in a heavy storm?
If you design the normal level of the pond and a high level that can handle excess flow you have no more of an issue than you would without the pond.
In fact in many places if you pave an area or build you have to install a pond to handle water that the area paved would normally drain.
So your issue is more what is the normal pond level and what is the storm pond level and how fast can I allow this higher level to drain after a storm.

Also every pond should have a overflow designed into it for worse case storms.

That's the problem exactly. How do I design the overflow on something that is going to have the dam at the exact edge of my property???

P.S. I have taken some measurements and It looks like I can make this thing 40x100'. Pretty large.