Bare riverbanks are a big problem because every time a water even happens the powerful water flow rips the bank away, making the river wider and more shallow.
Push back soil, reform into a 45 degree angle, plant bank vegetation. This will allow water to climb up the bank instead of washing against it this decreases erosion. Improving plant cover on the bank will also improve erosion control.
This buildup of marshy substance otherwise know as "Silt" ruins spawning grounds for trout by covering gravel were eggs are laid. This happens when the water flow is slow and erosion upstream, allowing particles to fall down and build up in an area.
Excessive Siltation can be fixed with wing deflectors and J-hooks. narrow the stream and forcing the water through a smaller area increasing flow increased flow forces silt downstream. J-hooks serve the same purpose increasing flow.