I think FishinRod was suggesting that allowing the creek to run through the old pond basin may be of some help to remove the deposits the flooding left. However, that would depend on how much lower the downstream elevation is for the deposits to wash to.
The old pond was probably much deeper when it was first dug to be 5’ 80+ years later. I would suspect that when you excavate, you will hit thick layers of muck trapped under the new deposits to deal with if they were not washed out. I would have a plan on how to deal with that possibility.
Good luck, and looking forward to seeing the results!
