A morphology study of Makapuʻu Beach with a lidar topographic survey buggy

Abstract

This thesis investigates short-term beach morphology at Makapuʻu Beach, Oʻahu, in response totwo distinct wave events using a combination of high-resolution mobile LiDAR surveys and process-based wave modeling. A custom-built survey buggy equipped with RTK-GPS and LiDAR was developed to enable efficient topographic data collection across the beach face. Surveys were conducted before, during, and after each event to capture dynamic changes in beach elevation and sediment distribution. The first event, a relatively long-period north swell, caused substantial erosion and offshore sediment transport, particularly in the northern embayment. The second event, driven by moderate trade wind energy from the northeast, resulted in more uniform retreat and greater sediment retention. V olume change calculations and elevation differencing revealed spatial patterns of erosion, scarp formation, and partial recovery. These patterns are closely mirrored by XBeach Non-Hydrostatic (XBNH) model outputs, which show wave energy focusing, offshore-directed currents, and circulation features that help explain the spatial distribution of sediment loss and accumulation across the beach in each case. This study highlights the effectiveness of integrating mobile LiDAR and numerical modeling for high-resolution, event-scale beach monitoring. The results underscore the influence of incident wave characteristics on morphological response and provide valuable insights for shoreline management, sediment transport studies, and coastal engineering applications.