In an experimental program investigating cut edge striation generation during AWJ (abrasive water jet) cutting, mild steel and aluminium alloy samples have been cut with a range of process parameters and the resulting cut edge striation carefully analysed to develop a phenomenological model of striation generation based on variations in the geometry of the cut front. The existence of a range of moving steps on the cut front has been confirmed by the use of high speed video recording of the cut front when cutting transparent materials.