Dave & Meadowlark,
I decided to proceed with a willow-ectomy.
I took the willow off of the dam. I was suprised to see a lot of the roots running parallel to the dam. I hooked them to the back hoe and pulled them out. Most of the roots, >75% were on the surface at the stump. It was amazing how the roots that were in the water were massive matts of roots, like carpet. I guess soil contact is not necessary with a willow. Naturally there were some that went back into the dam. I pulled as many as possible and cut the rest off. The stump pulled relatively easily. The root ball that was with it was shallow, but very wide. I guess time will tell if I alleviated a problem or created one.
Ron
