The most important advantage after eliminating freeze heave IMO is to be able to easily adjust the freeboard level on the dam.
Earth dams, no matter what soil composition and how well compacted during construction, have a tendency to settle/compact more on their own over time. The part of the dam that has the most fill settles the most. I had to lower my vertical riser one time because of this issue. I measured how much I wanted/needed to cut off while the water was still going over the top edge of the riser. Then during the summer when the water level was a bit lower than the amount I needed to cut off I took and old handsaw to the pipe and cut it off in a couple minutes. No digging involved.
Getting quick ground cover established on the bare dirt around the pond is the best solution to keeping erosion from getting back into the pond.
It takes years to get a balanced ecosystem in a pond so mucking it out needs to be avoided if possible more than once every 20-30 years.
Fish are pretty tough but leaving their hiding places and nests undisturbed is the best when possible.
Ron
