MS Plan A Defense: Nonhydrostatic XBeach Simulation of Wave Transformations in a Fringing Reef Environment: Validation using Field Observations

Charlotte White
Master’s Student
Department of Ocean and Resources Engineering
University of Hawai’i at Mānoa

**This defense will be held both in person (POST 723) and over Zoom**
Meeting ID: 924 2221 6911
Passcode: CharMS
https://hawaii.zoom.us/j/92422216911

Modeling wave transformations in nearshore fringing reef environments is a highly evolving field, especially for engineering applications. This study focuses on wave transformation at Waimānalo Beach, a location that features a shallow fringing reef and sloping seafloor. To study the wave characteristics at the site, the nonhydrostatic version of XBeach (nonhXB), a two-dimension, depth-integrated numerical model is implemented. The offshore boundary wave conditions are provided by the Simulating Waves Nearshore (SWAN) model. The bathymetry for the nonhXB model is prepared using USACE 1-m resolution LiDAR data, while the bathymetry for the SWAN model is prepared with the NOAA 3-m resolution Continuously Updated Digital Elevation Model. This study adopts an approach by integrating in-situ field observations at Waimānalo Beach, as a method of calibrating the nonhXB model setup for the site. Waves at two nearshore locations were measured using pressure transducers. The results of the field survey reveal infragravity (IG) waves present at both pressure sensor locations. Using spectral input from a nearby offshore wave buoy, the ability of nonhXB to simulate IG waves is explored. The study also examines how bottom roughness affects the nonhXB model results, in particular, the IG waves.