frost lines and shallow ponds

Back about 12 years or so, we had a real bad cold snap run through the
Portland Or. area.
My pond at the time was3 feet deep, 12 wide, and agetr a week of sub zero
tems, I had 9 inches of ice on my pond. I enjoyed walking on my pond and
getting a perspective on it I normally would.
The only problem I did have was ice dams in my falls, and a bit of water
loss one night...
Bear