Not sure if this is something the community here has interest in.
A section of the creek bank has fallen away, revealing that all of the soil has been recently deposited (~ last few decades). The garbage inclusion likely spreads for dozens or maybe hundreds of cubic meters of earth. We don't want to disturb the soil to clean this out so we're limited to surface level cleaning.
On the flipside: it's lots of deep fertile topsoil. The fast growing weeds, like lantana, absolutely love it.
You think it's all channelised and cut under that? About the same height?
Is this a drainage reserve or a gully? Not a lot of water there. Does the watercourse have its own reserve or does it push up against property? If it has room to move, you can try some techniques from "Let the water do the work" - https://quiviracoalition.org/2018/03/06/erosion-control/ - https://quiviracoalition.org/2018/03/06/induced-meandering/ - https://quiviracoalition.org/product/let-the-water-do-the-work-induced-meandering-and-evolving-method-for-restoring-incised-channels/
Getting local government to be involved is difficult, did you make any headway? Guerilla gardening is usually the only thing that works on the small scale.
Any rocks out of the watercourse around? Big enough that the flow of water won't move them? Battering with a mattock, shovelling the soil up to the flat, mass planting at 10cm centres with your local sedges and grasses (as close as you can get them), and protecting the toe with some bigger rocks is how I would do it if it wasn't a crazy large area.
You are going to plant behind the creek edge? Like clear up to/near edge and regenerate?