It sounds like you have more watershed than the pond size can handle. My pond has more than I'd like and I struggle with muddy waters. A 4 foot rise in water with only 3 inches of rain sound like you have way too much water shed. I have thought about cutting a channel (ditch) that diverts some of my watershed so that it does not go to the pond, but, like you, I wonder if it would be better to just spend the money on another pond. I think trenchin to divert water would be better than creating dams (or swells) so think about that instead. I'm living fine with my situation for now as my pond is technically a water retention pond so that my front yard does not flood when we get a couple of days of heavy rain.
