Just to offer some food for thought:

Where I go grouse hunting in WI, I run by these risers installed by the state all over the place in the flooded marshes/canals that they use to control the water and drain it as well. Most are only 3-4 feet deep however several are 8-15 feet deep and all seem to be functioning fine. And I know they get some ice up there. I have thought of installing one in my own pond (when it gets built) but from what I have seen, is that they leak between the boards which makes me wonder on the effectiveness of the device.