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Chris Houser - One of the best experts on this subject based on the ideXlab platform.
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post storm beach and dune recovery implications for barrier island resilience
Geomorphology, 2015Co-Authors: Chris Houser, Phillipe A Wernette, Elizabeth Rentschlar, Hannah Jones, Brianna Hammond, Sarah TrimbleAbstract:Abstract The ability of beaches and dunes to recover following an extreme storm is a primary control of barrier island response to sea-level rise and changes in the frequency and/or magnitude of storm surges. Whereas erosion of the beach and dune occurs over hours and days, it can be years to decades before the beach and dune are able to recover to their pre-storm state. As a consequence, there are numerous descriptions of near-instantaneous beach and dune erosion due to storms, the immediate onshore transport of sand, and the initial phases of beach and dune recovery following a storm, but a paucity of data on long-term beach and dune recovery. A combination of previously published data from Galveston Island, Texas and new remotely sensed data from Santa Rosa Island, Florida is used in the present study to quantify the rate of dune recovery for dissipative and intermediate beach types, respectively. Recovery of the dune height and volume on Galveston Island was observed within two years following Hurricane Alicia (1983) and was largely complete within six years of the storm, despite extensive Washover. In contrast, the dunes on Santa Rosa Island in Northwest Florida began to recover four years after Hurricane Ivan (2004), and only after the profile approached its pre-storm level and the rate of vegetation recovery (regrowth) was at a maximum. Results show that complete recovery of the largest dunes (in height and volume) will take approximately 10 years on Santa Rosa Island, which suggests that these sections of the island are particularly vulnerable to significant change in island morphology if there is also a change in the frequency and magnitude of storm events. In contrast, the areas of the island with the smallest dunes before Hurricane Ivan exhibited a rapid recovery, but no further growth in profile volume and dune height beyond the pre-storm volume and height, despite continued recovery of the largest dunes to their pre-storm height. A change in storm magnitude and/or frequency is a potential threat to barrier island resilience, particularly for those sections of the island where dune recovery has historically taken the longest time. Further study is required to determine how and why dune recovery varies for the dissipative and intermediate beaches of Galveston Island and Santa Rosa Island, respectively.
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initiation and evolution of blowouts within padre island national seashore texas
Ocean & Coastal Management, 2014Co-Authors: Mallorie Jewell, Chris Houser, Sarah TrimbleAbstract:Abstract Blowouts once covered the entire northern section of North Padre Island as a result of overgrazing, but are now restricted to a 5.5 km length of beach where driving is permitted between the low water line and the toe of the foredune. A comparison between this driving section and a directly adjacent non-driving section of the beach reveals a significant difference in the ratio of storm run-up (Rhigh) to the elevation of the dune toe (Dlow), suggesting that the foredunes within the driving section are more susceptible to scarping and blowout development. Where driving is permitted, blowouts are located in areas where Rhigh/Dlow ratio is locally large, suggesting that the location of blowouts depends on the alongshore variation in storm surge. Results of a cluster analysis reveal two distinct blowout types, in which the relatively small blowouts of Cluster 1 are characterized by a small throat and limited expansion beyond the foredune. The large and more active blowouts of Cluster 2 tend to be found closer to the access road, where driving on the beach is more concentrated and the larger Rhigh/Dlow suggests a greater potential for scarping during relatively small storms. The development of these blowouts feeds back on the height of the foredune, making it susceptible to scarping and Washover during tropical storms and hurricanes. It is argued that historical overgrazing and recent beach driving have significantly altered this landscape and represents a long-term threat to island resilience and have the potential to hasten island transgression with sea level rise.
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alongshore variation in the morphology of coastal dunes implications for storm response
Geomorphology, 2013Co-Authors: Chris HouserAbstract:Abstract The geomorphological impact of an extreme storm on a barrier island tends to be modeled using a single cross-shore transect and dependent only on the elevation of the storm surge relative to the height of the dune. The foredune line, however, is rarely uniform and can exhibit considerable variation in height and width alongshore at a range of length scales. The purpose of this modeling study is to determine how alongshore variations in dune height affect barrier island response to extreme storms. The MIKE21 wave and current model is used to predict the morphological response of Matagorda Peninsula, Texas in response to storm surges associated with dune scarping, Washover and inundation. The extent and degree of dune-scarping, Washover and shoreline erosion is predicted for each storm scenario, with respect to the base morphology of the island and low-pass filtered forms in which small-scale topographic variance is removed. Results suggest that small variations in the height of an otherwise alongshore uniform foredune act as overwash conduits and are unstable, leading to a more variable duneline that is more susceptible to change by subsequent storms. The vertical development of the Washover gaps in the duneline is limited and eventually replaced by a lateral expansion that erodes adjacent dunes and leads to a more uniform island elevation. The loss of island elevation is greater for the (original) unfiltered alongshore profile, but relatively uniform duneline is the most unstable and exhibits the greatest morphological change. The different alongshore profile responses suggest that the impact of an extreme storm is sensitive to initial conditions and specifically the pre-storm variability of the crest elevation alongshore. This in turn suggests that the evolution of barrier islands is dependent on storm history until the variability in the duneline elevation reaches a maximum. Further study of barrier island response to storm sequencing with and without post-storm recovery, however, is required to understand the evolution and form for the prototype island.
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feedback between ridge and swale bathymetry and barrier island storm response and transgression
Geomorphology, 2012Co-Authors: Chris HouserAbstract:Abstract The shoreface of Santa Rosa Island in northwest Florida is characterized by a ridge and swale bathymetry that forces an alongshore variation in beach and dune morphology. The alongshore variation in dune morphology in turn controls the modern island response to and recovery from tropical storms and hurricanes, and is therefore, an important control on island transgression with relative sea-level rise. Field sampling and remote sensing are used in the present study to describe the geologic framework of Santa Rosa Island, and to elucidate on the origins of the shore-attached ridge and swale bathymetry. Vibracores and seismic and GPR surveys were completed along 42 cross-shore transects and 3 shore-parallel transects to examine the structure of the 21 ridge and swale structures found along Santa Rosa Island. The shore-parallel seismic surveys reveal strong near-horizontal reflectors through the ridges at depths consistent with thick back-barrier muds extracted from vibracores taken across and along the ridges. Near-horizontal reflectors are identified in ground-penetrating radar (GPR) surveys between the ridges and cuspate spits along the back-barrier shoreline, but are not present in the narrow sections of the island landward of the swales. Continuation of the seismic surveys in the back-barrier also reveals near-horizontal reflectors at the cuspate spits that are characterized by seagrass beds, salt marsh and maritime forest. Consistent with the GPR survey, there is an absence of horizontal reflectors between cuspate spits where the Washover deposits extend to the back-barrier shoreline. It is argued that the ridge and swale bathymetry is a transgressive surface and the remnants of cuspate spits that are present along the back-barrier shoreline. In this respect, the cuspate spits had to first develop along the back-barrier shoreline and eventually evolve into the mud-cored ridges as the island transgressed with relative sea-level rise. Once the ridge and swale bathymetry emerged on the Gulf of Mexico shoreface it was able to reinforce the alongshore variation in dune height and storm response. It is further argued that the cuspate spits are reinforced by the shoreface ridges through alongshore transport of sediment from adjacent Washover fans although the ridge orientation suggests that the spits have migrated westward by ~ 750 m. In this respect, the alongshore variation in beach and dune morphology on this island is the expression of this large-scale feedback and suggests a top-down model in which meso-scale processes and landforms depend on the geologic context.
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controls on coastal dune morphology shoreline erosion and barrier island response to extreme storms
Geomorphology, 2008Co-Authors: Chris Houser, Cheryl Hapke, Stuart E HamiltonAbstract:Abstract The response of a barrier island to an extreme storm depends in part on the surge elevation relative to the height and extent of the foredunes which can exhibit considerable variability alongshore. While it is recognized that alongshore variations in dune height and width direct barrier island response to storm surge, the underlying causes of the alongshore variation remain poorly understood. This study examines the alongshore variation in dune morphology along a 11 km stretch of Santa Rosa Island in northwest Florida and relates the variation in morphology to the response of the island during Hurricane Ivan and historic and storm-related rates of shoreline erosion. The morphology of the foredune and backbarrier dunes was characterized before and after Hurricane Ivan using Empirical Orthogonal Function (EOF) analysis and related through Canonical Correlation Analysis (CCA). The height and extent of the foredune, and the presence and relative location of the backbarrier dunes, varied alongshore at discrete length scales (of ~ 750, 1450 and 4550 m) that are statistically significant at the 95% confidence level. Cospectral analysis suggests that the variation in dune morphology is correlated with transverse ridges on the inner-shelf, the backbarrier cuspate headlands, and the historical and storm-related trends in shoreline change. Sections of the coast with little to no dune development before Hurricane Ivan were observed in the narrowest portions of the island (between headlands), west of the transverse ridges. Overwash penetration tended to be larger in these areas and island breaching was common, leaving the surface close to the watertable and covered by a lag of shell and gravel. In contrast, large foredunes and the backbarrier dunes were observed at the widest sections of the island (the cuspate headlands) and at crest of the transverse ridges. Due to the large dunes and the presence of the backbarrier dunes, these areas experienced less overwash penetration and most of the sediment from the beachface and dunes was deposited within the upper-shoreface. It is argued that this sediment is returned to the beachface through nearshore bar migration following the storm and that the areas with larger foredunes and backbarrier dunes have smaller rates of historical shoreline erosion compared to areas with smaller dunes and greater transfer of sediment to the Washover terrace. Since the recovery of the dunes will vary depending on the availability of sediment from the Washover and beachface, it is further argued that the alongshore pattern of dune morphology and the response of the island to the next extreme storm is forced by the transverse ridges and island width through alongshore variations in storm surge and overwash gradients respectively. These findings may be particularly important for coastal managers involved in the repair and rebuilding of coastal infrastructure that was damaged or destroyed during Hurricane Ivan.
Deirdre E Hart - One of the best experts on this subject based on the ideXlab platform.
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storm response of a mixed sand gravel beach ridge plain under falling relative sea levels a stratigraphic investigation using ground penetrating radar
Earth Surface Processes and Landforms, 2019Co-Authors: Sebastian J Pitman, James Shulmeister, Deirdre E HartAbstract:Beach ridge stratigraphy can provide an important record of both sustained coastal progradation and responses to events such as extreme storms, as well as evidence of earthquake induced sediment pulses. This study is a stratigraphic investigation of the late Holocene mixed sand gravel (MSG) beach ridge plain on the Canterbury coast, New Zealand. The subsurface was imaged along a 370 m shore-normal transect using 100 and 200 MHz ground penetrating radar (GPR) antennae, and cored to sample sediment textures. Results show that, seaward of a back-barrier lagoon, the Pegasus Bay beach ridge plain prograded almost uniformly, under conditions of relatively stable sea level. Nearshore sediment supply appears to have created a sustained sediment surplus, perhaps as a result of post-seismic sediment pulses, resulting in a flat, morphologically featureless beach ridge plain. Evidence of a high magnitude storm provides an exception, with an estimated event return period in excess of 100 years. Evidence from the GPR sequence combined with modern process observations from MSG beaches indicates that a palaeo-storm initially created a Washover fan into the back-barrier lagoon, with a large amount of sediment simultaneously moved off the beach face into the nearshore. This erosion event resulted in a topographic depression still evident today. In the subsequent recovery period, sediment was reworked by swash onto the beach as a sequence of berm deposit laminations, creating an elevated beach ridge that also has a modern-day topographic signature. As sediment supply returned to normal, and under conditions of falling sea level, a beach ridge progradation sequence accumulated seaward of the storm feature out to the modern-day beach as a large flat, uniform progradation plain. This study highlights the importance of extreme storm events and earthquake pulses on MSG coastlines in triggering high volume beach ridge formation during the subsequent recovery period.
Bernadette Tessier - One of the best experts on this subject based on the ideXlab platform.
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internal architecture and evolution of bioclastic beach ridges in a megatidal chenier plain field data and wave flume experiment
Sedimentology, 2013Co-Authors: Pierre Weill, Dominique Mouaze, Bernadette TessierAbstract:Beach ridges in macrotidal environments experience strong multi-annual to multi-decennial fluctuations of tidal inundation. The duration of tide flooding directly controls the duration of sediment reworking by waves, and thus the ridge dynamics. Flume modelling was used to investigate the impact of low-frequency tidal cycles on beach ridge evolution and internal architecture. The experiment was performed using natural bioclastic sediment, constant wave parameters and low-frequency variations of the mean water level. The morphological response of the beach ridge to water level fluctuations and the preservation of sedimentary structures were monitored by using side-view and plan-view photographs. Results were compared with the internal architecture of modern bioclastic beach ridges in a macrotidal chenier plain (Mont St. Michel Bay, France) surveyed with ground-penetrating radar. The experimentally obtained morphologies and internal structures matched those observed in the field, and the three ridge development stages identified in ground-penetrating radar profiles (early transgressive, late transgressive and progradational) were modelled successfully. Flume experiments indicate that flat bioclastic shapes play a key role in sediment sorting in the breaker zone, and in sediment layering in the beach and Washover fans. Water level controls Washover geometry, beach ridge evolution and internal structure. Low water levels allow beach ridge stabilization and sediment accumulation lower on tidal flats. During subsequent water level rise, accumulated sediment becomes available for deposition of new Washover units and for bayward extension of the beach ridges. In the field, low-frequency water level fluctuations are related to the 4·4 year and 18·6 year tidal cycles. Experimental results suggest that these cycles may represent the underlying factor in the evolution of the macrotidal chenier coast at the multi-decadal to centennial time scale.
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shelly cheniers on a modern macrotidal flat mont saint michel bay france internal architecture revealed by ground penetrating radar
Sedimentary Geology, 2012Co-Authors: Pierre Weill, Dominique Mouaze, Bernadette Tessier, Chantal Bonnotcourtois, Christophe NorgeotAbstract:Abstract The relationship between short-term morphodynamics and internal structure of shelly chenier ridges is investigated using ground-penetrating radar and core X-ray analysis, complemented with a comparison of aerial photographs. These cheniers are located on the uppermost part of a macrotidal flat in Mont-Saint-Michel bay (North-Western France). They actively migrate landward over the salt-marshes by Washover processes when they are submerged during the coincidence of spring tides and enhanced wave activity. The architecture of the cheniers is imaged using high-frequency radar antennas (400 MHz to 2.6 GHz). Three types of cheniers are recognized, featuring differences in morphology and internal structure. The altitude of the banks on the tidal flat relative to the level of tidal flooding, as well as local sediment supply, seem to be important forcing parameters in chenier development and stages of evolution. On a multi-annual time scale, evolution of this chenier system is influenced by a combination of the 18-year and the 4-year tidal cycles, superimposed on wave activity. During minima of the 18-year cycle, spring tide level is globally lower on the tidal flat, allowing salt marsh progradation and chenier ridge development. During peak periods of the tidal cycle, former barriers are reworked by wave action and experience onshore migration associated with salt marsh erosion. The 4-year tidal cycle coupled with enhanced wave activity is probably responsible for the deposition of large Washover units, observed in GPR reflection profiles.
Sebastian J Pitman - One of the best experts on this subject based on the ideXlab platform.
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storm response of a mixed sand gravel beach ridge plain under falling relative sea levels a stratigraphic investigation using ground penetrating radar
Earth Surface Processes and Landforms, 2019Co-Authors: Sebastian J Pitman, James Shulmeister, Deirdre E HartAbstract:Beach ridge stratigraphy can provide an important record of both sustained coastal progradation and responses to events such as extreme storms, as well as evidence of earthquake induced sediment pulses. This study is a stratigraphic investigation of the late Holocene mixed sand gravel (MSG) beach ridge plain on the Canterbury coast, New Zealand. The subsurface was imaged along a 370 m shore-normal transect using 100 and 200 MHz ground penetrating radar (GPR) antennae, and cored to sample sediment textures. Results show that, seaward of a back-barrier lagoon, the Pegasus Bay beach ridge plain prograded almost uniformly, under conditions of relatively stable sea level. Nearshore sediment supply appears to have created a sustained sediment surplus, perhaps as a result of post-seismic sediment pulses, resulting in a flat, morphologically featureless beach ridge plain. Evidence of a high magnitude storm provides an exception, with an estimated event return period in excess of 100 years. Evidence from the GPR sequence combined with modern process observations from MSG beaches indicates that a palaeo-storm initially created a Washover fan into the back-barrier lagoon, with a large amount of sediment simultaneously moved off the beach face into the nearshore. This erosion event resulted in a topographic depression still evident today. In the subsequent recovery period, sediment was reworked by swash onto the beach as a sequence of berm deposit laminations, creating an elevated beach ridge that also has a modern-day topographic signature. As sediment supply returned to normal, and under conditions of falling sea level, a beach ridge progradation sequence accumulated seaward of the storm feature out to the modern-day beach as a large flat, uniform progradation plain. This study highlights the importance of extreme storm events and earthquake pulses on MSG coastlines in triggering high volume beach ridge formation during the subsequent recovery period.
Aart Kroon - One of the best experts on this subject based on the ideXlab platform.
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storm flood impacts along the shores of micro tidal inland seas a morphological and sedimentological study of the vesterlyng beach the belt sea denmark
Geomorphology, 2016Co-Authors: Lars B Clemmensen, Aslaug C Glad, Aart KroonAbstract:Abstract The morphological and sedimentological impacts of an extreme storm event (‘Bodil’ in December 2013) were investigated at a mixed sand and gravel beach (Vesterlyng) in a micro-tidal environment along the Belt Sea, Denmark. The storm response was characteristic for mixed sand and gravel beaches: gravelly storm berms with sandy to gravelly Washover fans were formed at the upper beach where swash processes dominated during extreme water levels in combination with overtopping and overwash. In addition, storm scarps and gravel flats were formed. The elevation of the storm berm crest was identical to a summation of the still-water level (1.60 m) in the Belt Sea during the storm flood and the wave run-up (0.75 m) at the shore. The crest of 2.35 m is therefore a precise measure of the storm flood level. This storm flood was classified as a large-scale extreme event. In a Holocene perspective it is suggested that storm berm (beach ridge) heights above contemporaneous sea level can be used as a proxy of past flood events along micro-tidal shores.