The 5 km region of coastline that experienced the most erosion during the storm was spatially correlated with a region of persistent and irregular outer-surf zone and nearshore bathymetry. More than half of the original shoreline erosion recovered along 50% of the study site within 24 hours of the storm peak as waves remained large (>2.5 m), but transitioned to long period swell. Data also indicate that the timing of erosion and accretion during storms may be strongly influenced by wave steepness. In contrast, spatial variations in beach volume change during the building portion of this storm were not explained well by either alongshore variations in wave height or predicted relative runup. Specifically, the amount of wave dissipation in the inner surf-zone, as measured using time-averages of X-band radar returns, explained 50% of the variability in beach volume change during the building portion of the storm. These data suggest that spatial variations (O(100m) alongshore) in shoreline and beach-volume change are related to alongshore variations in inner surf zone morphology, which alters the amount of wave dissipation alongshore. These changes were compared with simultaneous observations of surf- and swash-zone morphology as well as with modeled and observed wave parameters during the storm to analyze patterns of erosion and accretion. Observations of beach volume and shoreline change from terrestrial laser data were collected semi-daily during a Nor’Easter along 10 km of the Outer Banks of North Carolina. Intersection of the radar data with the laser data also provides data on spatial variations in the maximum swash excursion during the time of the survey. In addition, CLARIS provides spatial maps of wave direction from the radar data, and localized measurements of inner-surf zone wave height and shoreline setup from laser time-series.
Coastal Lidar and Radar Imaging System (CLARIS), is a fully-mobile remote sensing system designed to operate during storms and collect topography data of the beach from a terrestrial laser scanner as well as bathymetry data from X-band radar-derived wave celerity measurements, and surf- and swash-zone morphology data from time-averaged radar images. ``Pre-’’ and ``post’’-storm surveys likely underestimate the total impact of a storm on the beach. Anecdotal evidence suggests that at least during moderate storms, such as the frequent extratropical storms that batters the Outer Banks of North Carolina, significant amounts of recovery may occur while the storm continues and waves are still large. Storm-scale coastal change is traditionally observed using ``pre-’’ and ``post’’-storm surveys, making explicit observations of processes driving alongshore variability in erosion and accretion during the storm difficult.
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