What about renting a scraper?
Don't know your waterways are the size but that is definitely a possibility I will warn you a scraper is one of the harder things to really Master to cut grade really close. Or at least it was for me and I will still not even say I've mastered it cuz I just don't run one enough. If you've got a big enough tractor you might consider buying or renting a pan.
Would you might be calling a scraper I'm trying to upload some pictures and I have such little service here at the house I'm having a tough time.
