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1. Determining depth of closure based on time-series beach profiles and empirical formulas: A case study along the Florida coast

   https://doi.org/10.34237/1009111  

   Royer, Elizabeth; Wang, Ping; Cheng, Jun (January 2023, Shore & Beach)

   Depth of closure (DOC) is defined as the most landward depth seaward of which there is no significant change in bed elevation and no significant net sediment exchange between the nearshore and the offshore over a certain period of time, such as 5 to 20 years. DOC is an essential parameter used in beach and shore protection, sediment management, and many other aspects of coastal studies. Taking advantage of advancements in wave hindcast and bathymetry measurement in the past 20 years (2000-2019), this study determined the DOC at 12 locations along the Florida coast, including three from the northwest Gulf coast, three from the west Gulf coast, and six from the east Atlantic coast. The 12 sites covered a wide range of coastal morphodynamic conditions, with considerable difference in tidal ranges, incident wave heights, as well as nearshore and offshore morphology. Hindcast wave data from WAVEWATCHIII, available since 2005, were analyzed and applied to calculate the closure depth using various empirical formulas. At all the 12 study sites, time-series profiles demonstrated an apparent convergence point indicating the presences of a DOC. The bed-level change at DOC, as quantified by the standard deviation of elevation variation, ranged from 0.05 m to 0.19 m. Along the studied northwest Florida Gulf coast the DOC ranged from 9.12 m to 9.76 m. The DOC along the studied west Florida Gulf coast ranged from 1.59 m to 4.06 m and is influenced by the shallow flat inner continental shelf. Along the studied east Florida Atlantic coast, the DOC ranged from 4.35 m to 8.20 m, with considerable alongshore variation. The Birkemeier formula yielded the closest predictions to the measured values. A linear relationship between the seaward slope of the outer bar and DOC was identified. Incorporating the seaward slope of the outer bar into the Birkemeier formula improved the accuracy of DOC prediction. 

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2. Factors controlling longshore variations of beach changes induced by Tropical Storm Eta (2020) along Pinellas County beaches, west-central Florida

   https://doi.org/10.34237/1008929  

   Cheng, Jun; Toledo Cossu, Francesca; Wang, Ping (January 2021, Shore & Beach)

   Tropical Storm Eta impacted the coast of west-central Florida from 11 November to 12 November 2020 and generated high waves over elevated water levels for over 20 hours. A total of 148 beach and nearshore profiles, spaced about 300 m (984 ft) apart, were surveyed one to two weeks before and one to eight days after the storm to examine the beach changes along four barrier islands, including Sand Key, Treasure Island, Long Key, and Mullet Key. The high storm waves superimposed on elevated water level reached the toe of dunes or seawalls and caused dune erosion and overwash at various places. Throughout most of the coast, the dune, dry beach, and nearshore area was eroded and most of the sediment was deposited on the seaward slope of the nearshore bar, resulting in a roughly conserved sand volume above closure depth. The longshore variation of beach-profile volume loss demonstrates an overall southward decreasing trend, mainly due to a southward decreasing nearshore wave height as controlled by offshore bathymetry and shoreline configurations. The Storm Erosion Index (SEI) developed by Miller and Livermont (2008) captured the longshore variation of beach-profile volume loss reasonably well. The longshore variation of breaking wave height is the dominant factor controlling the longshore changes of SEI and beach erosion. Temporal variation of water level also played a significant role, while beach berm elevation was a minor factor. Although wider beaches tended to experience more volume loss from TS Eta due to the availability of sediment, they were effective in protecting the back beach and dune area from erosion. On the other hand, smaller profile-volume loss from narrow beach did not necessarily relate to less dune/ structure damage. The opposite is often true. Accurate evaluation of a storm’s severity in terms of erosion potential would benefit beach management especially under the circumstance of increasing storm activities due to climate change. 

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3. Post-Hurricane Michael damage assessment using ADCIRC storm surge hindcast, image classification, and LiDAR

   https://doi.org/10.34237/1008741  

   Davis, Joshua; Mitsova, Diana; Briggs, Tynon; Briggs, Tiffany (January 2019, Shore & Beach)

   null (Ed.)

   Wave forcing from hurricanes, nor’easters, and energetic storms can cause erosion of the berm and beach face resulting in increased vulnerability of dunes and coastal infrastructure. LIDAR or other surveying techniques have quantified post-event morphology, but there is a lack of in situ hydrodynamic and morphodynamic measurements during extreme storm events. Two field studies were conducted in March 2018 and April 2019 at Bethany Beach, Delaware, where in situ hydrodynamic and morphodynamic measurements were made during a nor’easter (Nor’easter Riley) and an energetic storm (Easter Eve Storm). An array of sensors to measure water velocity, water depth, water elevation and bed elevation were mounted to scaffold pipes and deployed in a single cross-shore transect. Water velocity was measured using an electro-magnetic current meter while water and bed elevations were measured using an acoustic distance meter along with an algorithm to differentiate between the water and bed during swash processes. GPS profiles of the beach face were measured during every day-time low tide throughout the storm events. Both accretion and erosion were measured at different cross-shore positions and at different times during the storm events. Morphodynamic change along the back-beach was found to be related to berm erosion, suggesting an important morphologic feedback mechanism. Accumulated wave energy and wave energy flux per unit area between Nor’easter Riley and a recent mid-Atlantic hurricane (Hurricane Dorian) were calculated and compared. Coastal Observations: JALBTCX/NCMP emergency-response airborne Lidar coastal mapping & quick response data products for 2016/2017/2018 hurricane impact assessments 

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4. Alongshore variability in wave runup and inner surfzone wave conditions on an intermediate beach

   https://doi.org/10.1016/j.coastaleng.2025.104822  

   O’Dea, Annika; Raubenheimer, Britt; Brodie, Katherine; Elgar, Steve (December 2025, Coastal Engineering)

   Alongshore and temporal variability in wave runup and inner surfzone wave conditions are investigated on an intermediate beach using lidar-derived elevation transect timeseries. The lidar scanners were deployed at two alongshore locations separated by ε330 m at the U.S. Army Engineer Research and Development Center Field Research Facility in Duck, NC and collected 30 min (41 min) linescan time series at 7.1 Hz (5 Hz) each hour over an 11-day period before, during, and after Hurricane Matthew in October 2016. Runup and water surface- elevation time series at the estimated 0.5-m depth contour were used to determine the extreme runup 𝜔2% , the mean runup and inner surfzone water surface elevation, and the significant runup and inner-surf wave heights across sea-swell, infragravity, and all frequency bands. Offshore wave conditions were determined from an array of pressure gauges located in ε8-m water depth. Results show that the significant wave height in the sea- swell frequency band 𝜀𝜗𝜗 was intermittently depth-limited in the inner surf zone, with the ratio of significant sea-swell wave height in the inner surf zone to that in about 8-m depth (𝜀𝜗𝜗,𝜛𝜗𝜚 /𝜀𝜗𝜗,8 m ) ranging from 0.42 to 1.31 during low-energy conditions and from 0.19 to 0.39 during high-energy conditions. Significant temporal variability in runup parameters was observed over the 11-day period, with 𝜔2% ranging from 1.07 to 3.07 m at the southern lidar location and from 1.45 to 3.36 m at the northern lidar location. Alongshore differences in 𝜔2% ranged from 0.00 to 0.90 m, with both 𝜔2% and the significant swash height 𝜔𝜍𝜑𝛻 typically larger at the northern lidar location. Alongshore variability in most inner surfzone and runup parameters was largest during low-energy offshore wave conditions when the inner surf zone was unsaturated, although this trend was weakest in 𝜔2%. The mean runup elevation 𝜔𝜕ℵℶℷ above the still water level was only weakly correlated with the wave-driven super-elevation of the water surface in the inner surf zone (𝜚𝜕ℵℶℷ , R2 = 0.23), suggesting that wave-breaking-induced setup is only one factor contributing to 𝜔𝜕ℵℶℷ . Although the significant sea-swell swash height 𝜔𝜗𝜗 and alongshore differences in 𝜔𝜗𝜗 were correlated with foreshore beach slope ℸ⊳ ⊲0ℵ𝜍1⊲0ℵ (R2 = 0.59 and R2 = 0.70, respectively), 𝜔2% , 𝜔𝜕ℵℶℷ , and alongshore variations thereof were uncorrelated with ℸ⊳ ⊲0ℵ𝜍1⊲0ℵ. 𝜔2% and 𝜔𝜕ℵℶℷ were correlated with the significant wave height in the inner surf zone 𝜀𝜍𝜑𝛻,𝜛𝜗𝜚 (R2 = 0.61 and R2 = 0.72, respectively), which is strongly influenced by wave dissipation patterns across the surf zone. These results suggest that while ℸ⊳ ⊲0ℵ𝜍1⊲0ℵ affects the magnitude of swash oscillations about the mean, it has a smaller role in the total elevation reached by runup on intermediate beaches. Furthermore, the results illustrate the importance of surfzone bathymetry and the resulting temporal and alongshore variations of inner surfzone wave heights to the extreme and mean runup. 

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5. Field Observations of Surfzone Vorticity

   https://doi.org/10.1029/2024GL111402  

   Dooley, C; Elgar, Steve; Raubenheimer, Britt (October 2024, Geophysical Research Letters)

   Abstract In the surfzone, breaking‐wave generated eddies and vortices transport material along the coast and offshore to the continental shelf, providing a pathway from land to the ocean. Here, surfzone vorticity is investigated with unique field observations obtained during a wide range of wave and bathymetric conditions on an Atlantic Ocean beach. Small spatial‐scale [O(10 m)] vorticity estimated with a 5 m diameter ring of 14 current meters deployed in ∼2 m water depth increased as the directional spread of the wave field increased. Large spatial‐scale [O(100 m)] vorticity calculated from remote sensing estimates of currents across the surfzone along 200 m of the shoreline increased as alongshore bathymetric variability (channels, bars, bumps, holes) increased. For all bathymetric conditions, large‐scale vorticity in the inner surfzone was more energetic than in the outer surfzone. 

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