It is part of a river system, but I don’t think it has a huge effect on the ice moving, i may be wrong. I think it has more to do with the size of the lake. The ice gets pushed around from the wind and gives way in spots creating pressure ridges and open cracks. There are also spots that have underwater springs that prevent the ice from forming properly. If it looks like there is a ridge that goes a long distance, I would do my best to stay away from it. I also would stay away from points and shallow rocky areas. The rocks can actually heat up the water from the sunlight and melt the ice from underneath. The points might have some current around them also creating weak ice. I have already heard of a couple trucks going through on Last Mountain. In fact I was sent a couple pics of two trucks going through today.