Rapid-response observations on barrier islands along Cape Fear, North Carolina, during Hurricane Isaias

Abstract

Hurricane Isaias struck the Cape Fear Region of North Carolina around 23:00 EDT on 3 August 2020, making landfall at Ocean Isle Beach as a Category 1 storm with peak wind speeds of 80 mph. An array of nearshore Sofar Spotter wave buoys captured the wave field at two beaches off the coasts of Bald Head Island (south-facing and east-facing beaches) and Masonboro Island. Local variations in significant wave height and peak wave direction were observed along the Lower Cape Fear Region, due to large shoal features impacting the regional wave climate. A cross-shore transect of five pressure sensors was installed at the north end of Masonboro Island 2.5 days prior to landfall to measure storm surge, wave runup, and variation of gravity/ infragravity wave energy across the barrier island. The three fast-sampling wave gauges along the backshore became buried before Hurricane Isaias peak storm surge, and the two gauges on and behind the dune were never inundated. A low-cost (< $250) Storm Surge Observation Camera (SSOC) prototype captured storm surge and coastal erosion at Kure Beach, in conjunction with pre- and post-storm RTK GPS beach profile surveys. Kure Beach experienced more than 1.0 m of vertical erosion of the berm, while Masonboro Island experienced around 0.1 m of accretion across the backshore, despite nearly identical wave and wind forcing conditions at the two beaches separated by ~20 km. Pre-storm berm height and width (higher and wider at Kure Beach), as well as foreshore slope (steeper, 1:9, at Kure Beach), are likely factors influencing significant erosion at Kure Beach, while slight accretion was observed at Masonboro Island.

Hazard assessment and hydrodynamic, morphodynamic, and hydrological response to Hurricane Gamma and Hurricane Delta on the northern Yucatán Peninsula

“…Field observations provide valuable information to improve our understanding of the drivers and coastal response during extreme events (e.g., Valle-Levinson et al, 2002;Du et al, 2019;Mieras et al, 2021). Previous studies have demonstrated the important role of compound flooding driven by rain, storm surge, and groundwater processes (e.g., Wahl et al, 2015;Valle-Levinson et al, 2020;Housego et al, 2021).…”

Beach Profile, Water Level, and Wave Runup Measurements Using a Standalone Line-Scanning, Low-Cost (LLC) LiDAR System

“…Advancing our understanding of storm processes and impacts will require novel instrument platforms for better observations of sediment transport processes and hydromorphodynamics [7]. Traditional methods for surveying beach profile elevation and shoreline evolution have a low temporal resolution, with days, weeks, or months between measurements, due to logistical and economic constraints [15][16][17], and can typically only be employed before and after a storm, but not during, when the most rapid morphological changes occur [18]. Developing a more complete understanding of storm processes requires sensors capable of (a) continuously measuring beach profile evolution and total water levels (wave runup, wave setup, tide, and storm surge) before, during, and after a storm with higher spatial and temporal resolution than traditional methods, and (b) withstanding high wind, energetic waves, and/or sediment accretion/erosion [19].…”

“…Alternatively, ultrasonic sensors have also been used to measure beach elevation changes over time, before, during, and after storm impact [19,28]. Modern terrestrially based LiDAR systems are still largely cost prohibitive and require a level of infrastructure that makes rapid deployment unfeasible or impractical, particularly on remote barrier islands which may serve to protect the hinterland [18]. A prototype rapidly deployable Line-scanning, Low-Cost (LLC) LiDAR system was developed in 2020 at the University of North Carolina Wilmington to provide an affordable method of collecting beach profile and free-surface elevation data with reasonably high spatial and temporal resolution and minimal infrastructure requirements.…”