If your job has "fill" which fits in the category of silt, sand and gravel and it has washed away, as at the original stream bed, replacing and compacting the same material won't work, due to that experience. Many bridge folks use large rip-rap, sometimes well graded in size to fit the velocity of flow expected, However, that is not always possible so using the largest size you an muster is common, not always successful permanently and requiring occasional replacing with more. Remember the increased flow velocity due to the restriction the bridge imposes.
