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Storms and extremely energetic events may significantly impact the form and structure of beaches, and so cause erosive processes and coastal damages. Efficient management actions require an up-to-date and accurate knowledge of beach morphological changes, with the shoreline position being a good indicator of such changes. This work proposes the use of the open-source Shoreline Analysis and Extraction Tool (SAET) software for the definition of satellite-derived shorelines (SDSs) from L8 and Sentinel-2 imagery to reveal the shoreline position changes at the beaches of the Ebro Delta, NE Spain. Spatial-temporal models (STMs) of shoreline changes enable a characterisation of how the beaches responded to the storms of 2020. In conjunction with wave data, STMs enable an analysis of the erosive response to storm events, as well as a monitoring of subsequent beach recovery in the short and medium term (<1 year). Results show how Storm Gloria (January 2020, Hs max = 7.62 m) acted as a disruptive event and shifting point in the shoreline trend. As a response to that storm, major erosive processes occurred along the delta that caused an average shoreline retreat of 47 m. A progressive recovery during the spring and summer was mainly associated with periods of low wave energy. Nevertheless, by the end of the year a complete recovery had been achieved for about half of the coast, while the other half showed an average erosion of more than 10 m when compared to the pre-storm situation. Both the erosive and the recovery processes took place unevenly on different sections of the coast, probably dependent on factors such as the orientation of the beach and the pattern of longitudinal sediment transport along the coast. • Automatic shoreline extraction from Sentinel 2 and Landsat 8 imagery using SAET. • Pre and post-storm characterisation of SDS position in time and space using STMs. • Storm Gloria (January 2020) caused an unprecedented and heterogeneous impact on the Ebro Delta. • Slow recovery occurred in the months following the event conditioned by orientation and wave patterns. • About half of the delta showed a significant shoreline retreat by the end of 2020. [ABSTRACT FROM AUTHOR]

Coastal dunes provide many ecosystem services including protection of infrastructure from wave overtopping and habitat for native species. Foredunes grow at different rates and assume different forms (i.e., short and wide to tall and narrow) depending on a range of factors including pre-existing beach and dune morphology, wind, wave, and water levels, sediment grain size, and vegetation characteristics, yet the relative importance of these factors on foredune growth is understudied. Here, we quantify foredune evolution (2016–2019) and explore the relative influence of a suite of metocean, sedimentary, and ecological factors for dune growth on three barrier islands in the U.S. North Carolina Outer Banks (Cape Lookout National Seashore). We incorporate observed and hindcast wind, wave, and water level data into the process-based, coupled beach-dune evolution model, Windsurf, to explore the relative contribution of factors likely to influence foredune growth at the annual timescale (2016–2017). Our cross-shore topographic profile observations show varied interannual foredune change rates and characteristics, including horizontal retreat and progradation at the dune toe and vertical erosion and accretion at the dune crest. Model results indicate that, of the factors explored, pre-existing morphology had the greatest influence on the type of foredune growth that occurred (i.e., incipient dune development, widening of the dune, and/or vertical accretion), which dramatically altered the final shape of the dune. Variations in wind and wave climates were associated with the relative contribution of marine- and aeolian-driven bed elevation changes and were particularly influential during storms. In addition, increases in the minimum elevation of vegetation on the dune profile (analogous to the cross-shore distance between the shoreline and established vegetation line, i.e., the vegetation limit, as coined by Duran and Moore, 2013) increased dune crest height and dune volume. Moreover, variations in the minimum vegetation elevation resulted in a larger range of dune crest elevations and dune volumes than differences in the median sand grain size. We suggest that insights into the relative influence of metocean, sedimentary, and ecological factors to dune growth can assist in the development of practical coastal management strategies. • Pre-existing beach-dune morphology had the largest influence on dune growth type. • Exposure to the dominant wave direction led to increased dune volume. • Higher minimum vegetation elevation and finer sand resulted in taller dunes. • Minimum vegetation elevation influenced dune growth more than sand grain size. [ABSTRACT FROM AUTHOR]

Shorelines bordering ebb deltas are often subject to deformation by the approach and attachment of ebb-tidal shoals. Although this is a common behaviour, little attention has been paid to the link between shoal migration and the multi-annual development of the adjacent beach-dune system. This study aims to understand beach-dune systems' behaviour during the approach phase of an ebb-tidal shoal attachment event. Topographic and bathymetric data of the barrier island of Texel (NL) was used to calculate shoreline position, beach and dune volume, dunefoot position, and shoal displacement rates. Two classical beach-dune interaction models were used to understand the observed behaviour: the surfzone-beach-dune model and the sediment budget model. The analysis revealed how a larger bank on the land-facing side of the ebb delta split into two smaller shoals with different morphological behaviours. One of the shoals (S1) moved consistently landwards, recently attaching the shore, whereas the second shoal (S2) is still evolving and presents a milder landward movement than S1. In parallel to the landward movement of S1, the adjacent coastline was subject to erosion, partially counterbalanced by nourishments. However, despite the erosion, dunes are growing in volume, suggesting a net positive transfer of sand from the beach to the dunes. In the surfzone-beach-dune model, regular nourishments positively affect beach state by maintaining sufficient beach size for aeolian sediment transport and reducing shoreline erosion. In the budget model, dune volume growth may occur despite a slightly negative beach budget. Framing Texel in the budget model implies that the beach budget before the start of the approach phase is crucial in defining the behaviour of the dune system during this phase. If the shoal approach significantly reduces the beach budget, the system may cross the budget threshold that dune building is possible. Thus, the dune system may evolve to an erosional state, including dune ridge dissection and blowout development. Hence, nourishments have been essential in keeping the current morphological state during the attachment of the shoal, as they restrict the system from crossing the negative morphological threshold. Thus, without the nourishments, beach erosion driven by the shoal might have led to morphological changes in the dune system that could lead to years of a weakened level of protection until foredune recovery after attachment. • Shoal-induced changes in beach budget influence dune development. • Dune morphology may change depending on the beach state prior to attachment. • Nourishments can retain beach budget at a sufficient level to maintain dune morphology. [ABSTRACT FROM AUTHOR]

Erosion rates along Alaska's Beaufort Sea coast, among the highest in the world, are negatively impacting communities, industrial and military infrastructure, and wildlife habitat. Decreasing maximal winter ice extent and increasing summer open water duration and extent in the Beaufort Sea may be making the coast more vulnerable to destructive storm waves than during recent, colder, icier decades. Previous studies of Beaufort Sea coastal change have been limited to subaerial analyses of the shoreline. Here we describe nearshore seafloor change by comparing post-World War II (WWII) (1945-53) bathymetry data to recently acquired (1985–2018) bathymetry data and relate the observed seafloor change to adjacent shoreline change near Utqiagvik, within Stefansson Sound, and immediately west of Barter Island and Kaktovik. Within the Utqiagvik region, seabed erosion was generally highest (>1.0 m of loss) offshore of Point Barrow and along the eastern end of the Tapkaluk Islands, while there were lesser amounts of deposition (<0.5 m of gain) within the protected waters of Elson Lagoon. Sedimentation was generally highest offshore of Point Barrow, in a region of converging currents, and on the landward side of the barrier islands and spits fronting Elson Lagoon, which is likely related to a regional trend of westerly sediment transport and landward migration of the barrier islands. Within Stefansson Sound, perhaps the most notable changes from post-WWII bathymetry data compared to recent data are a switch from mixed, low erosion and deposition in 1997 to low deposition (<0.5 m) in 2018 east of the Boulder Patch, a switch from low erosion in 1997 to neutral depth change in 2018 in the channel between the north and south Boulder Patch areas, and higher deposition from 1997 to 2018 landward of the rapidly retreating barrier islands along the Sound's northern border. At Barter Island, high erosion near north-facing shorelines and high deposition near west-facing shorelines generally matched shoreline changes. One of our goals is to identify possible processes responsible for the depth changes we quantified. Using simple metrics that relate sediment characteristics with modeled waves and non-wave induced currents, we show that sediment resuspension and transport by both wave and non-wave driven currents likely contribute to the overall patterns of change within the ∼13 m isobath along the open coast, and that the influence of wave action affecting sediment transport is expanding seaward. • Patterns of decadal-scale changes in shoreline positions and bathymetry indicate possible linkages within the nearshore. • Depth changes are additionally driven by sediment resuspension and transport by both wave and non-wave driven currents. • Wave action affecting sediment transport expanded seaward and deepened by as much as 15 cm/yr between 1979 and 2019. [ABSTRACT FROM AUTHOR]