REGIONAL GEOLOGIC MAPPING OF THE COASTAL ZONE TO IDENTIFY AND QUANTIFY COASTAL HAZARDS

An ongoing cooperative coastal research program is delineating the geologic framework of northeastern North Carolina and seeking to understand the physical processes driving the evolution of the coast. The long-term program goal is to acquire comprehensive knowledge of this coastal system, including the estuaries, barrier islands, and inner continental shelf. This knowledge will be used to understand the linkage of geologic framework and physical processes to coastal evolution and possibly predict the coastal response to oceanographic and climatic forcing at time scales from storm events to centuries. Many of the research tasks are focused on, or can be used to identify and quantify, coastal hazards. Shoreline change (SWASH) monitoring provides information on the spatial and temporal response of the ocean shoreline to storm events, and provides insight into erosion hazard areas along the immediate shoreline. Nearshore geophysical surveys have linked erosion hotspots to specific surf zone morphologies that may recur over time due to interactions between physical processes and the shallow geologic framework. Ground-penetrating radar studies can identify pre-historic and historic inlet locations that may be reoccupied in future storms. Geomorphic mapping using historical air photos and recent LIDAR data shows the evolution of landform types, the impact of humans on the landscape, and resulting changes in coastal vulnerability to storms and long-term shoreline change. Geophysical surveys of the inner continental shelf provide an understanding of the geologic history of the coastal system, furnish insight into coastal sediment flux, and identify sand resources for mitigating erosion hazards through beach nourishment. Regional geologic mapping shows that the underlying geologic framework of Quaternary sediments determines the availability and distribution of sediment in this coastal system and controls the overall barrier island geomorphology. For example, sediment-rich coastal segments have high, wide, accretionary barriers dominated by beach ridges, while sediment-starved coastal segments have narrow, washover-dominated barriers. Recognizing coastal hazards as a function of geologic setting and physical processes allows sound planning of hazard mitigation strategies.