I have a pretty large outflow pipe (15" PVC) and used an inlet water control structure from AgriDrain. I have not had any problems with it for a couple winters, but it is pricy. However, you can control how much rise you want in 4" increments. I had an established pond with an existing emergency spillway. This device allowed me to raise the water level gradually over three years to just the level I wanted. All in all it was a cheap way for me to get a pond with greater depth.
