from the info supplied, I would basically build a dike (wall) of larger rocks, boulders,and would backfill. I would start the backfill by using sod, or what have you,green side to the rocks. the grass would continue to grow,holding the soil in place, and the rocks would hold the grass.

You'll also want to address the root cause of the erosion, or all your work may be for naught. Is there more water flowing through the stream than in the past? Did someone upstream do something to change the flow? Slowing down the stream, such as by placing bits of log in the stream, can help stop streams from cutting down and creating canyons. But it depends on the overall factors affecting why your stream is causing erosion, which could depend on a number of things.