I have never fished Hickory so I haven't witnessed the problems, but I understand what you guys are wanting to do. My thought would be to start a Stream Team. I don't know much about these either but it could be used as a platform to put some extra pressure on the city to do the right thing. Scheduling a cleanup on the stream and posting it here would probably bring many volunteers. Through the stream team you could also conduct water quality samples that could also put more pressure on the city to do the right thing.
As far as over harvesting, good luck. It seems the best way to cut down on this is through education. It appears the Smallmouth Alliance has had some success with their free the fighter signs at popular accesses. Something like that could be done to educate the public so they understand the problems of over harvesting. Of course then you have people that just don't care, I see them all the time.