Shoreline Change and Pacific Climatic Oscillations in Kihei, Maui, Hawaii

ROONEY, J.J.B., and FLETCHER, C.H. III, 2004. Shoreline change and Pacific climatic oscillations in Kihei, Maui, Hawaii. Journal of Coastal Research, 21(0), 000–000. West Palm Beach (Florida), ISSN 0749-0208. Increasing demands on coastal areas require enhanced understanding of coastal erosion hazards. Here we analyze a 5-km segment of the Kihei coastline (Maui, Hawaii) centered on an area of chronic coastal erosion. A high-resolution database of variations in shoreline sediment volume over the past century reveals a complex and dramatic pattern of changes between 1900 and 1997. Comparisons of historical sediment erosion and accretion at barriers to longshore transport are used to estimate longshore sediment fluxes over this period. In the absence of detailed long-term oceanographic and meteorological data for the site, fluctuations in the magnitude and direction of net longshore sediment transport (NLST) are a potentially valuable resource for investigating why documented changes have occurred. Available data suggest that observed patterns of NLST reflect multidecadal variations in Kona storm (strong, rain-bearing winds from the southwest) activity. These storms appear to be modulated by the Pacific Decadal Oscillation (PDO), which has a tendency to alter atmospheric circulation such that Kona storm activity in the vicinity of the Hawaiian Islands is reduced during its positive phase. Correlations among the PDO cycle, Kona storm activity, and NLST in Kihei, and the apparent inability of other possible forces to produce the observed patterns of NLST, suggest a causeand-effect relationship. Consideration of the PDO may improve our understanding of coastal sediment dynamics in many areas, enhancing existing efforts to forecast erosion hazard areas and effectively manage sandy shorelines. ADDITIONAL INDEX WORDS: Shoreline change, beach erosion, Kona storm, Pacific Decadal Oscillation.