SEASONAL WAVE CLIMATE ANOMALIES ON THE NORTH SHORE INDICATIVE OF EROSION CONDITIONS

Abstract

In recent years, ocean inundation has impacted local infrastructure at Sunset Beach, O`ahu especially when the beach is highly eroded. The objective of this thesis is to explain and identify potential drivers of erosion. Given a lack of sediment observations at Sunset Beach, this study uses a combination of numerical modeling, buoy observations, sediment characteristics, US Army Corps of Engineers Honolulu District’s remote sensing observations, and anecdotal evidence from local community observers to identify the erosion drivers. The seasonal cycle of the wave environment which drives the beach dynamics is dramatic, with large waves in December-March and small waves in May-August. This study relates seasonal wind, wave, and water level anomalies to the recent erosion and negligible erosion years using the various datasets. The wave and wind fields have the largest deviations from the climatological seasonal cycle in the May-August preceding the dramatic erosion which occurs during September-December. The largest and most significant changes are related to the local trade winds variability varying +14% to -23% from the climatological reference. These findings suggest the summer conditions help (or hinder) the beach recovery to endure (or suffer) the average erosive wave conditions experienced in the winter months.