Tom,
I understood your reference to changing the bank from the surface/edge to ~3". That will certainly reduce the horizontal surface area in that zone. I think in the process of digging to change the slope you would get most of the cattails out thus getting very close to your permanent solution.
Any new growth would likely be very minor and could be easily maintained by pulling the growth out.
What kind of bottom do you have? I am not familiar with the soil in your area. If I were to do that in my pond the soil in the high slope area would tend to collapse and even the bottom out again.
Good luck and please do be careful if you are going to excavate. I lost a co-worker in a rollover when he was excavating his pond a few years back.
Cheers,
JW
