One possibility, if the normal stream flow is very low, is to pave/gravel (with big gravel) a low area that actually dips down into the stream. Just use some small culverts or plastic pipes to carry the normal flow and let it overflow when a gully washer comes along. If it's low and sturdy enough, it may not wash out but would be easy to fix if a little does. This is the route I went in building a crossing over a little spring/pond-overlfow-fed stream beside my property. It hasn't suffered an overflow yet to test it out. It's only 7' wide. My tractor is only 4' wide. Used concrete bags along the sides above the PVC pipes. Just cut away the bag material at the top and wet them to solidify.
Ralph