Beach response, shoreline water levels, and surf-zone hydrodynamics measured during Hurricane Dorian in Duck, NC

Katherine L Brodie1, Patrick Dickhudt1, Nicholas Cohn2, Britt Raubenheimer3, Brittany Lynn Bruder2, Nick Spore1, Levi Gorrell4, Ian Conery5 and Steve Elgar3, (1)U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, Duck, NC, United States, (2)U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, Field Research Facility, Duck, United States, (3)Woods Hole Oceanographic Institution, Woods Hole, MA, United States, (4)Woods Hole Oceanographic Institution, Applied Ocean Physics & Engineering, Woods Hole, United States, (5)U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, Duck, United States
Abstract:
Hurricane Dorian made landfall on Cape Hatteras, NC at 0935 EDT on September 6th, 2019 as a category 1 hurricane, 70 miles south of the U.S. Army Engineer Research and Development Center’s Field Research Facility (FRF) in Duck, NC. Continuous observations from long-term gauges and rapidly deployed supplemental sensors quantified surf-zone hydrodynamics, morphology change, and meteorological conditions at the FRF. Sustained winds at the end of the 600-m long pier exceeded category 1 strength for 1.75 hours, peaking at 36.5 m/s from the north at 1050 EDT with a maximum gust of 43.8 m/s. Offshore significant wave heights measured in 26-m depth peaked at 6.9 m at 1133 EDT, making Dorian the 4th largest wave event at the FRF since 1985. Wave heights peaked 3 hours before high tide (1414 EDT), 4 hours before the peak surge of ~ 1 m (1542 EDT), and exceeded 4 m for 8 hours (0830-1630 EDT). Shoreline water levels were measured with terrestrial lidar, stereo imagery, and in-situ pressure sensors on four cross-shore transects on the 1-km-long FRF property. At the northern transect, total water level (wave runup, tide, and surge) peaked near 4 m NAVD88 between 1200-1330 EDT. Morphological response was measured with vessel-based GPS and sonar 2 days before and 3 days after the storm, and with fixed terrestrial lidars continuously during the storm. Despite the large offshore waves, impacts to the dunes at the FRF were minimal. Beach response varied spatially, with erosion of 1 m vertically on the summer berm and accretion of 0.1 m near the dune toe. Initial recovery of the lower beach (0.5 m accretion) at the northern transect was rapid, occurring within 48 hours of the storm peak. Regional mobile terrestrial lidar surveys were performed 2 days before and 4 days after the storm along 40-km surrounding the FRF. Further analysis will explore the scales of spatial variability in storm-driven hydrodynamics and beach response during Dorian. Funded by USACE, NSF, USCRP, and ASD(R&E).