Rhythmic patterns:
Look for repeated patterns of erosional areas adjacent (in a longshore direction) to accretional areas. These are likely due to the presence of giant cusps in one of the surveys and either a) giant cusps in the other survey were not present or b) were shifted alongshore. During storms, wave runup in low embayments between adjacent cusps may attack dunes, causing net erosion, whereas landward of prominent cusps the dunes may be protected by the wide beach.