Alongshore Variable Accretional and Erosional Coastal Foredune Dynamics at Event to Interannual Timescales

Abstract

Foredunes are common landforms on many sandy beaches that develop from the complex interplay of marine, aeolian, ecological, and anthropogenic processes. The magnitude of accretional inputs to coastal dunes is dependent on wind properties (e.g.,

Total water level controls on the trajectory of dune toe retreat

“…5). These complex patterns in dune impacts are consistent with the findings of other observational studies focused on quantifying spatial variability in dune volume changes across the Outer Banks, with hotspot dune erosion locations often found to be correlated with steep pre-storm foreshore slopes and/or complex nearshore bathymetry (e.g., Cohn et al, 2021Cohn et al, , 2022b. Where dune erosion did occur, the results of this study indicate that TWL may be a predictor of the trajectory of dune toe retreat.…”

“…However, north of the property, the beach and dune are actively managed through beach nourishment and dune vegetation planting, including a beach nourishment conducted during the study period which was completed just weeks before the impact of Maria (2017). Within the FRF property, the dunes in the northern section have been eroding since 2000, including a retreat of 25 m from 2003 to 2014 and ~1 m between 2015 and 2017, but the dunes in the southern section have vertically accreted and prograded over the same interval (Brodie et al, 2019;Cohn et al, 2022b). Dune heights within the property and the rest of the study site generally reach 6-8 m elevation (relative to NAVD88), while dune toes are typically at ~3-4 m (e.g., Brodie and Spore, 2015).…”

“…Observations of beach and dune morphology have been collected regularly in the vicinity of the FRF since 2011 using the Coastal Lidar and Radar Imaging System (CLARIS; Cohn et al, 2022b). The CLARIS system includes a Riegl VZ-2000 terrestrial Lidar scanner, inertial measurement unit (IMU), and global positioning system (GPS) mounted atop a vehicle (currently a van).…”

Quantifying coastal evolution and project performance at beaches by using satellite imagery

“…The most recent time period is predominantly characterized by severe nor'easter impacts where shorelines receded 10-15 m from storm impacts. These extratropical impacts span long duration stormy periods and often cause more erosion than tropical systems, also noted by Cohn et al (2022).…”

“…The timestack (Figure 35) shows the increase in shoreline width following initial construction that started within the monitored area in May 2017. Immediately after construction, alongshore dispersion of the nourishment to the south occurs beyond the nourishment project bounds (also shown in Cohn et al 2022). Figure 35 shows erosion within the nourished zone beginning approximately 11 months after project construction (Figure 35).…”