OCEANFRONT AND ESTUARINE SHORELINE CHANGE AND ITS LINKAGE TO EBB DELTA REPOSITIONING: RICH INLET, NC

In their natural state, inlets have the capacity to promote significant oceanfront as well as estuarine shoreline changes through complex linkages to the ebb-tidal delta. Beach nourishment is a critical management concern for areas within these inlet hazard zones. Chronic erosion and use of tidal inlets for sand resources are major issues. An exemplary inlet that has exerted a considerable influence on shoreline change and is the focus of management concerns is Rich Inlet. This relatively large inlet separates Figure 8 Island, a private residential island, from Hutaff Island, an undeveloped barrier.

The inlet has been relatively stable, its movement confined to a 1.0km migration pathway. As a result, the flood-tidal delta is highly asymmetric (0.15-0.35 x 3000m) and is bordered by two large channels. Although dredging activities have excavated sand from one of the channels for nourishment purposes, stringent regulations involving large-scale mining within estuaries preclude the use of the flood tidal delta and interior channels. As a consequence more costly efforts involving the ebb delta as a long-term source have been proposed. In an effort to ascertain the extent of the inlet’s influence, an analysis of aerial photographs was undertaken which indicated that since 1938 the throat has shifted a net distance of 510m to the northeast; 325m of the migration has occurred since 1993. The most recent period of migration coincided with a change in the orientation of the outer-bar channel from SSE to ENE. The consequences of this movement for the Figure Eight Island oceanfront are twofold: first and foremost, swash bar complexes no longer nourish the island’s developed segment; and secondly, the ebb delta no longer affords protection from wave attack. As a result, the northern 2.0km of oceanfront, which has a 70-year history of accretion, eroded more than 110m. Sand transport pathways in the soundside channels are also affected by migration and realignment of the throat section that controls the location of the flood ramp and ultimately the locus of shoaling within the estuarine channels.

Alteration of the inlet is a controversial issue and modification of the system without an understanding of the linkage between the shoals, adjacent shorelines, and the estuary will result in significant changes in the entire sand sharing system.