Major processes structuring the Vineyard’s south shore through supply, erosion, and transport of sand and materials (above). Waves strike the shore obliquely and then retreat perpendicularly (yellow arrows); longshore currents transport sand primarily in an easterly direction (light blue arrows); under higher tides and storm conditions, waves overwash the beach transporting sand into coastal ponds and migrating the beach inland (red arrow); following a breach tidal currents flow into and out of coastal ponds.