Following the model of Cacchione and others (1984), we infer that the enhanced bottom stresses produced by an intensified quasisteady current (e.g., downwelling currents due to storm set-up) and oscillatory flows (waves) are capable of transporting gravelly shellhash across the shoreface of Wrightsville Beach during storms, where it is concentrated in the floors of RSDs. Such currents may be laterally restricted or topographically enhanced (Cacchione and Drake 1990). The finer-grained sand in between the RSDs should also be mobilized during these storm events. However, the enhanced erosion within the RSDs due to the greater surface roughness, with localized scour around sediment particles on the bed, must inhibit deposition of fine sediment, thus maintaining the general morphology and textural quality of the RSDs. This provides a possible explanation for the apparent morphologic stability of the RSD through time (Figures 7 and Figure 8). The formation and maintenance of the RSDs may also involve cross-shore processes operating at the kilometer-scale of the entire shoreface. For example, variations in island shape (a concave- to convex-seaward shape change at the middle of the island (see Figure 1) and the presence of a large jetty and ebb-tidal delta complex at the downdrift end of the island may enhance seaward-directed flows during storm events from the northeast, as water accumulates in the bight formed by the jetty/delta and island. Thus, the excess water may escape the shoreface via strong downwelling currents that are topographically controlled by these larger-scale physiographic features, as well as the nearshore ridges (Figure 1) and smaller-scale RSD topography (Figures 1, Figure 7 and Figure 9 ). Topographic steering of downwelling flows has also been suggested by Cacchione and Drake (1990) for RSDs on the northern California shelf.