Here are some pics of the structure I put in over the weekend.
Last evening I also added one piece of 15"x5' culvert and I have three more to roll in.
Our pond is about 3 years old and we added the first fish Mar 2010 we just bought the place last fall. The pond bottom was completely smooth when built.
Depends. If they stay under water (not exposed to air) they last longer. My guess is those larger branches will last about 3 years , smaller ones maybe 2.