Stationary LiDAR observations and modeling of runup, inner-surf zone waves, and beach morphology during energetic storm events

Lauren Kim1, Katherine L Brodie2, Julia W Fiedler3, Sarah N Giddings4, Robert T Guza3 and Mark A Merrifield5, (1)Scripps Institution of Oceanography, UC San Diego, La Jolla, CA, United States, (2)U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, Duck, NC, United States, (3)University of California San Diego, Scripps Institution of Oceanography, La Jolla, United States, (4)Scripps Institution of Oceanography, La Jolla, CA, United States, (5)Scripps Institution of Oceanography, La Jolla, United States
Abstract:
Water level and beach elevation were observed with a stationary LiDAR sampling at 7 Hz during Hurricane Jose (9/18/17-9/21/17) and a Nor’Easter (2/7/2016-2/11/2016) at the U.S. Army Corps of Engineers Field Research Facility in Duck, NC. This extensive data set allows us to investigate the morphological response of the foreshore beach and the hydrodynamic components of runup and inner-surf zone (ISZ, located at the base of the swash zone) waves during energetic storm events. In both events, offshore incident wave heights reached ~4 meters at a pressure sensor array in 8-m water depth. During Hurricane Jose, hourly observations of the sub-aerial beach showed periods of upper beach accretion and lower beach erosion, which may be related to an existing scarp at the hurricane onset. LiDAR-observed significant ISZ wave heights reached a maximum of 0.8 meters with infragravity (IG) and seaswell (SS) components of similar magnitude. However, the runup during this storm event was IG dominated, with the IG component nearly twice that of the SS component. During the Nor’Easter, the entire sub-aerial beach profile eroded during the first half of the storm, with upper beach accretion and lower beach erosion occurring during the latter half. This switch from erosive to accretive regimes possibly corresponds to a change from IG dominated to SS dominated runup. ISZ significant wave heights in the SS band tended to be higher than in the IG band and reached a maximum of 1.25 meters. Empirical estimates of runup (based on foreshore beach slope and H0L0) were significantly correlated with observations. The IG runup component was generally well parameterized, but the SS and setup components were often underpredicted by up to ~50% and ~70%, respectively. Ongoing work, that combines observations and morphodynamic models, explores the relationship between ISZ wave heights, runup, and morphological change, and the drivers of error between observed and estimated runup.
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