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Gerhard Masselink - One of the best experts on this subject based on the ideXlab platform.
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the role of Beach Morphology on coastal cliff erosion under extreme waves
Earth Surface Processes and Landforms, 2018Co-Authors: Claire Earlie, Gerhard Masselink, Paul RussellAbstract:Erosion of hard-rock coastal cliffs is understood to be caused by a combination of both marine and sub-aerial processes. Beach Morphology, tidal elevation and significant wave heights, especially under extreme storm conditions, can lead to variability in wave energy flux to the cliff-toe. Wave and water level measurements in the nearshore under energetic conditions are difficult to obtain and in-situ observations are rare. Here we use monthly cliff-face volume changes detected using terrestrial laser scanning alongside Beach morphological changes and modelled nearshore hydrodynamics to examine how exposed cliffs respond to changes in extreme wave conditions and Beach Morphology. The measurements cover the North Atlantic storms of 2013-2014 and consider two exposed stretches of coastline (Porthleven and Godrevy, UK) with contrasting Beach Morphology fronting the cliffs; a flat dissipative sandy Beach at Godrevy and a steep reflective gravel Beach at Porthleven. Beach slope and the elevation of the Beach-cliff junction were found to influence the frequency of cliff inundation and the power of wave-cliff impacts. Numerical modelling (XBeach-G) showed that under highly energetic wave conditions, i.e. those that occurred in the North Atlantic during winter 2013–2014, with Hs = 5.5 m (dissipative site) and 8 m (reflective site), the combination of greater wave height and steeper Beach at the reflective site led to amplified wave run-up, subjecting these cliffs to waves over 4 times as powerful as those impacting the cliffs at the dissipative site (39 kWm-1 compared with 9 kWm-1). This study highlighted the sensitivity of cliff erosion to extreme wave conditions, where the majority (over 90% of the annual value) of cliff-face erosion ensued during the winter. The significance of these short-term erosion rates in the context of long-term retreat illustrates the importance of incorporating short-term Beach and wave dynamics into geomorphological studies of coastal cliff change.
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The role of Beach Morphology on coastal cliff erosion under extreme waves
Earth Surface Processes and Landforms, 2018Co-Authors: Claire Earlie, Gerhard Masselink, Paul RussellAbstract:Erosion of hard-rock coastal cliffs is understood to be caused by a combination of both marine and sub-aerial processes. Beach Morphology, tidal elevation and significant wave heights, especially under extreme storm conditions, can lead to variability in wave energy flux to the cliff-toe. Wave and water level measurements in the nearshore under energetic conditions are difficult to obtain and in situ observations are rare. Here we use monthly cliff-face volume changes detected using terrestrial laser scanning alongside Beach morphological changes and modelled nearshore hydrodynamics to examine how exposed cliffs respond to changes in extreme wave conditions and Beach Morphology. The measurements cover the North Atlantic storms of 2013 to 2014 and consider two exposed stretches of coastline (Porthleven and Godrevy, UK) with contrasting Beach Morphology fronting the cliffs; a flat dissipative sandy Beach at Godrevy and a steep reflective gravel Beach at Porthleven. Beach slope and the elevation of the Beach-cliff junction were found to influence the frequency of cliff inundation and the power of wave-cliff impacts. Numerical modelling (XBeach-G) showed that under highly energetic wave conditions, i.e. those that occurred in the North Atlantic during winter 2013-2014, with H-s = 5.5 m (dissipative site) and 8 m (reflective site), the combination of greater wave height and steeper Beach at the reflective site led to amplified wave run-up, subjecting these cliffs to waves over four times as powerful as those impacting the cliffs at the dissipative site (39 kWm(-1) compared with 9 kWm(-1)). This study highlighted the sensitivity of cliff erosion to extreme wave conditions, where the majority (over 90% of the annual value) of cliff-face erosion ensued during the winter. The significance of these short-term erosion rates in the context of long-term retreat illustrates the importance of incorporating short-term Beach and wave dynamics into geomorphological studies of coastal cliff change. (C) 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley and Sons Ltd.
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Large-scale laboratory investigation into the effect of varying back-barrier lagoon water levels on gravel Beach Morphology and swash zone sediment transport
Coastal Engineering, 2012Co-Authors: Gerhard Masselink, Ian L. TurnerAbstract:Abstract It is generally accepted that the effect on Beach Morphology of the interactions between swash motion and the Beach groundwater table depends on the elevation of the latter relative to that of the sea. Specifically, a low Beach groundwater table is considered to enhance onshore sediment transport and Beach accretion, while the reverse is thought to hold for a high Beach groundwater table. Here, we use the results of a carefully designed series of tests conducted in the Delta Flume, the Netherlands, as part of the Barrier Dynamics Experiment ( BARDEX ), to unequivocally demonstrate the validity of this assertion. During the experiment, a 4-m high and 50-m long gravel barrier ( D 50 = 11 mm) was constructed within the central region of the 250-m long and 7-m deep wave flume, enabling a back-barrier ‘lagoon’ to be located at its landward side. The groundwater table in the Beach was manipulated by lowering and raising the lagoon level, and the gravel Beach was subjected to variable wave conditions and sea/lagoon levels. Using as the initial Beach profile the Morphology resulting from 90 min of wave forcing with the sea and lagoon at the same level, the identical wave forcing with a low lagoon level consistently resulted in onshore sediment transport in the swash zone and Beach accretion, whereas the identical wave forcing with a high lagoon level consistently caused offshore sediment transport in the swash zone and Beach erosion. The divergent Beach morphological responses for the low and high lagoon levels could not be attributed to changes in the ‘bulk’ swash hydrodynamics (i.e., based on single-point velocity measurements) arising from a difference in the amount of swash infiltration into the unsaturated Beach. Instead, application of a sediment transport model that accounts for the effects of in/exfiltration suggested that the onshore sediment transport and Beach accretion for the low lagoon tests mainly resulted from enhanced bed shear stresses during the wave uprush due to infiltration into the saturated part of the Beachface. Due to the large hydraulic conductivity of gravel ( K = O (0.1 m s − 1 )), the effect of altered shear stresses due to in/exfiltration may be an important factor in sediment transport in the swash zone of gravel Beaches.
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test of edge wave forcing during formation of rhythmic Beach Morphology
Journal of Geophysical Research, 2004Co-Authors: Gerhard Masselink, Paul Russell, Giovanni Coco, D A HuntleyAbstract:[1] This paper reports on concurrent measurements of evolving rhythmic Beach Morphology and the associated water motion on a macrotidal, coarse sandy Beach. Beach cusps with a spacing of 19 m developed over a 3-day period of low-energy swell after which they were destroyed by energetic wind waves. The Beach cusps were clearly accretionary features and developed mainly during the rising tide. Detailed hydrodynamic measurements were conducted at three locations in the swash and inner surf zone in the vicinity of a developing cusp horn and revealed that energetic standing, mode-zero, subharmonic edge waves were not present during the initiation of the Beach cusps. Specifically, analysis of the hydrodynamic data indicated that: (1) the amount of subharmonic energy was limited (<10% of the total energy); (2) none of the computed energy spectra exhibited a significant peak at the subharmonic frequency; (3) the cross-shore velocity amplitude at the subharmonic frequency was 2–3 times larger than the longshore velocity amplitude; (4) the longshore current motion at the subharmonic frequency was barely coherent between adjacent locations in the surf zone; and (5) the time series of pressure and cross-shore current were in phase at either side of the developing cusp horn. It is concluded that, at least during this event of Beach cusp formation, energetic standing edge waves are not a prerequisite to initiate the development of rhythmic Beach Morphology.
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Test of edge wave forcing during formation of rhythmic Beach Morphology
Journal of Geophysical Research, 2004Co-Authors: Gerhard Masselink, Paul Russell, Giovanni Coco, D A HuntleyAbstract:[1] This paper reports on concurrent measurements of evolving rhythmic Beach Morphology and the associated water motion on a macrotidal, coarse sandy Beach. Beach cusps with a spacing of 19 m developed over a 3-day period of low-energy swell after which they were destroyed by energetic wind waves. The Beach cusps were clearly accretionary features and developed mainly during the rising tide. Detailed hydrodynamic measurements were conducted at three locations in the swash and inner surf zone in the vicinity of a developing cusp horn and revealed that energetic standing, mode-zero, subharmonic edge waves were not present during the initiation of the Beach cusps. Specifically, analysis of the hydrodynamic data indicated that: (1) the amount of subharmonic energy was limited (
N. Chandrasekar - One of the best experts on this subject based on the ideXlab platform.
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ONWET: A Simple Integrated Tool for Beach Morphology and Wave Dynamics Analysis
Marine Georesources & Geotechnology, 2015Co-Authors: V. Joevivek, N. ChandrasekarAbstract:The analysis of Beach profile combined with wave data provides a clear understanding of Beach topography and physical behavior of the coast. Numerous commercial and noncommercial computer programs and add-on tools are available to analyze Beach profile and wave data. But, most of them are specifically designed for particular coastal application. Moreover, searching of open source software for diverse coastal application is a tedious process. To make it easily accessible, we have developed an integrated Matlab GUI for Beach Morphology and wave analysis. The tool “ONWET (OceaN WavE Tool)” mainly includes wave processes, Beach Morphology, spatiotemporal variation in Beach profile, wave refraction, and sediment transport rate. The tool has automated inbuilt functions and is designed to accommodate importing/exporting of data (results both in data and graphical format). It includes user friendly options and can be freely download from our institutional website. The tool is very useful for researchers, scientis...
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Seasonal impact on Beach Morphology and the status of heavy mineral deposition – central Tamil Nadu coast, India
Journal of Earth System Science, 2014Co-Authors: V. Joevivek, N. ChandrasekarAbstract:The aim of the present research was to investigate the seasonal impact on nearshore Beach dynamics and the status of heavy mineral distribution along central Tamil Nadu coast, India. Beach profile measurements were made in 10 profiling sites between Thirukadaiyur and Velankanni on monthly and seasonal basis from January 2011 to July 2012. Using Beach profile data, variation in Beach width, slope and volumetric changes have been calculated. Beach slope and nearshore wave parameters were used to quantify the longshore sediment transport rate. Beaches between Thirukadaiyur and Karaikkal attained predominant transport rate in northern direction whereas, the rest of the Beaches are in southern direction. The seasonal action of wind and wave currents create nearshore bar during northeast (NE) monsoon and frequent berms at tidal zone during southwest (SW) monsoon. Surface sediment samples were collected in each location for quantifying the heavy mineral weight percentage during the period of pre- and post-Thane cyclone. Sediments were also studied by X-ray diffraction (XRD) to evaluate the changes and occurrence of heavy minerals in Beach sands. The XRD results show that sediments in the study area have enriched heavy mineral distribution even after strong cyclonic event. It confirms the redistribution of heavy mineral deposits present in the coast. The results suggested that monsoonal action has influenced the seasonal changes in Beach Morphology and it does not affect the heavy mineral distribution.
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seasonal impact on Beach Morphology and the status of heavy mineral deposition central tamil nadu coast india
Journal of Earth System Science, 2014Co-Authors: V. Joevivek, N. ChandrasekarAbstract:The aim of the present research was to investigate the seasonal impact on nearshore Beach dynamics and the status of heavy mineral distribution along central Tamil Nadu coast, India. Beach profile measurements were made in 10 profiling sites between Thirukadaiyur and Velankanni on monthly and seasonal basis from January 2011 to July 2012. Using Beach profile data, variation in Beach width, slope and volumetric changes have been calculated. Beach slope and nearshore wave parameters were used to quantify the longshore sediment transport rate. Beaches between Thirukadaiyur and Karaikkal attained predominant transport rate in northern direction whereas, the rest of the Beaches are in southern direction. The seasonal action of wind and wave currents create nearshore bar during northeast (NE) monsoon and frequent berms at tidal zone during southwest (SW) monsoon. Surface sediment samples were collected in each location for quantifying the heavy mineral weight percentage during the period of pre- and post-Thane cyclone. Sediments were also studied by X-ray diffraction (XRD) to evaluate the changes and occurrence of heavy minerals in Beach sands. The XRD results show that sediments in the study area have enriched heavy mineral distribution even after strong cyclonic event. It confirms the redistribution of heavy mineral deposits present in the coast. The results suggested that monsoonal action has influenced the seasonal changes in Beach Morphology and it does not affect the heavy mineral distribution.
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A Simple Computer Program for the Analysis of Beach Morphology and Morphodynamics
International journal of geoinformatics, 2009Co-Authors: N. ChandrasekarAbstract:each-profile surveying is a relatively long-established and widely utilised shoreline monitoring technique. Several computer programs are available to visualize the Beach profile data. But in all programs, the raw field data can’t be used to calculate the Beach Morphology, sediment volume, Beach erosion and accretion. In this manuscript, we describe the development of a simple program ‘THE Beach’ developed by using Visual Basic 6.0, that can store and analyze the profile data obtained from Emery pole or surveyor’s level surveys. This program calculates the elevation of different points along the profile transect and the data can be stored in a Microsoft access database file which is linked with the program It estimates the Beach morphological parameters such as Beach width, slope and sediment volume above any user specified datum. It also calculates the Beach sediment erosion and accretion made in a Beach by comparing another Beach profile data which is already stored in the database. This program is very useful to geologists, coastal mangers and environmentalists for coastal zone management and environmental impact assessment studies.
Ian L. Turner - One of the best experts on this subject based on the ideXlab platform.
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Large-scale laboratory investigation into the effect of varying back-barrier lagoon water levels on gravel Beach Morphology and swash zone sediment transport
Coastal Engineering, 2012Co-Authors: Gerhard Masselink, Ian L. TurnerAbstract:Abstract It is generally accepted that the effect on Beach Morphology of the interactions between swash motion and the Beach groundwater table depends on the elevation of the latter relative to that of the sea. Specifically, a low Beach groundwater table is considered to enhance onshore sediment transport and Beach accretion, while the reverse is thought to hold for a high Beach groundwater table. Here, we use the results of a carefully designed series of tests conducted in the Delta Flume, the Netherlands, as part of the Barrier Dynamics Experiment ( BARDEX ), to unequivocally demonstrate the validity of this assertion. During the experiment, a 4-m high and 50-m long gravel barrier ( D 50 = 11 mm) was constructed within the central region of the 250-m long and 7-m deep wave flume, enabling a back-barrier ‘lagoon’ to be located at its landward side. The groundwater table in the Beach was manipulated by lowering and raising the lagoon level, and the gravel Beach was subjected to variable wave conditions and sea/lagoon levels. Using as the initial Beach profile the Morphology resulting from 90 min of wave forcing with the sea and lagoon at the same level, the identical wave forcing with a low lagoon level consistently resulted in onshore sediment transport in the swash zone and Beach accretion, whereas the identical wave forcing with a high lagoon level consistently caused offshore sediment transport in the swash zone and Beach erosion. The divergent Beach morphological responses for the low and high lagoon levels could not be attributed to changes in the ‘bulk’ swash hydrodynamics (i.e., based on single-point velocity measurements) arising from a difference in the amount of swash infiltration into the unsaturated Beach. Instead, application of a sediment transport model that accounts for the effects of in/exfiltration suggested that the onshore sediment transport and Beach accretion for the low lagoon tests mainly resulted from enhanced bed shear stresses during the wave uprush due to infiltration into the saturated part of the Beachface. Due to the large hydraulic conductivity of gravel ( K = O (0.1 m s − 1 )), the effect of altered shear stresses due to in/exfiltration may be an important factor in sediment transport in the swash zone of gravel Beaches.
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the practical application of four commercially available numerical Beach Morphology models on a high energy coastline
Coasts & Ports 1999: Challenges and Directions for the New Century; Proceedings of the 14th Australasian Coastal and Ocean Engineering Conference and , 1999Co-Authors: James T Carley, Ian L. Turner, Edward D Couriel, Langus Jackson, John McgrathAbstract:As part of the detailed design and impact assessment for the Northern Gold Coast Beach Protection Strategy Master Plan, the commercially available models SBeach and UNIBEST-TC were used to assess cross-shore Beach profile response, while GENESIS and UNIBEST-LT were used in the assessment of longshore sediment transport and coastline realignment. The scope for model verification is excellent since the Gold Coast has abundant wave and Beach profile data collected over more than 20 years. SBeach and UNIBEST-TC were verified against data from six storm events between 1988 and 1997, with both models able to predict measured erosion volumes with some degree of success. The cross-shore models were then used to assess the impact of a range of design storms. Neither cross-shore model was able to reliably reproduce measured Beach recovery during low wave conditions. Both GENESIS and UNIBEST-LT were used to simulate the widely accepted longshore transport rate of 500,000 m{3}/yr northward. GENESIS was used to model the impact of the proposed submerged reef on the shoreline alignment either side of it. UNIBEST-LT (with the Bijker sediment transport formula) was used to determine the crossshore distribution of longshore transport. All models used in this study are being continually refined and improved by their developers.
D A Huntley - One of the best experts on this subject based on the ideXlab platform.
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test of edge wave forcing during formation of rhythmic Beach Morphology
Journal of Geophysical Research, 2004Co-Authors: Gerhard Masselink, Paul Russell, Giovanni Coco, D A HuntleyAbstract:[1] This paper reports on concurrent measurements of evolving rhythmic Beach Morphology and the associated water motion on a macrotidal, coarse sandy Beach. Beach cusps with a spacing of 19 m developed over a 3-day period of low-energy swell after which they were destroyed by energetic wind waves. The Beach cusps were clearly accretionary features and developed mainly during the rising tide. Detailed hydrodynamic measurements were conducted at three locations in the swash and inner surf zone in the vicinity of a developing cusp horn and revealed that energetic standing, mode-zero, subharmonic edge waves were not present during the initiation of the Beach cusps. Specifically, analysis of the hydrodynamic data indicated that: (1) the amount of subharmonic energy was limited (<10% of the total energy); (2) none of the computed energy spectra exhibited a significant peak at the subharmonic frequency; (3) the cross-shore velocity amplitude at the subharmonic frequency was 2–3 times larger than the longshore velocity amplitude; (4) the longshore current motion at the subharmonic frequency was barely coherent between adjacent locations in the surf zone; and (5) the time series of pressure and cross-shore current were in phase at either side of the developing cusp horn. It is concluded that, at least during this event of Beach cusp formation, energetic standing edge waves are not a prerequisite to initiate the development of rhythmic Beach Morphology.
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Test of edge wave forcing during formation of rhythmic Beach Morphology
Journal of Geophysical Research, 2004Co-Authors: Gerhard Masselink, Paul Russell, Giovanni Coco, D A HuntleyAbstract:[1] This paper reports on concurrent measurements of evolving rhythmic Beach Morphology and the associated water motion on a macrotidal, coarse sandy Beach. Beach cusps with a spacing of 19 m developed over a 3-day period of low-energy swell after which they were destroyed by energetic wind waves. The Beach cusps were clearly accretionary features and developed mainly during the rising tide. Detailed hydrodynamic measurements were conducted at three locations in the swash and inner surf zone in the vicinity of a developing cusp horn and revealed that energetic standing, mode-zero, subharmonic edge waves were not present during the initiation of the Beach cusps. Specifically, analysis of the hydrodynamic data indicated that: (1) the amount of subharmonic energy was limited (
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The Influence of Long Waves on Macrotidal Beach Morphology
Coastal Engineering, 1997Co-Authors: David Simmonds, T. J. O'hare, D A HuntleyAbstract:The aim of the following paper is to demonstrate that standing long waves can generate intertidal morphological features in a dissipative macrotidal setting. In this environment the tidal excursion can exceed the length scales associated with long waves. This extends the work of Simmonds et al (1995) in which it was shown that monochromatic long waves could generate sediment convergence patterns that bore a good similarity to observed topographic features, namely ridges and runnels from a field site on the Belgian coast. The simulation is modified to include a band of long waves and it is found that a good correspondence with real topography can still be achieved on a tidally averaged basis by allowing for a degree of uncertainty in the breaking criterion. It is also argued why the observed scales are more likely to correspond with the shorter end of the long wave spectrum. The simulation helps to shed light on the conditions in which such features are known to form.
Paul Russell - One of the best experts on this subject based on the ideXlab platform.
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the role of Beach Morphology on coastal cliff erosion under extreme waves
Earth Surface Processes and Landforms, 2018Co-Authors: Claire Earlie, Gerhard Masselink, Paul RussellAbstract:Erosion of hard-rock coastal cliffs is understood to be caused by a combination of both marine and sub-aerial processes. Beach Morphology, tidal elevation and significant wave heights, especially under extreme storm conditions, can lead to variability in wave energy flux to the cliff-toe. Wave and water level measurements in the nearshore under energetic conditions are difficult to obtain and in-situ observations are rare. Here we use monthly cliff-face volume changes detected using terrestrial laser scanning alongside Beach morphological changes and modelled nearshore hydrodynamics to examine how exposed cliffs respond to changes in extreme wave conditions and Beach Morphology. The measurements cover the North Atlantic storms of 2013-2014 and consider two exposed stretches of coastline (Porthleven and Godrevy, UK) with contrasting Beach Morphology fronting the cliffs; a flat dissipative sandy Beach at Godrevy and a steep reflective gravel Beach at Porthleven. Beach slope and the elevation of the Beach-cliff junction were found to influence the frequency of cliff inundation and the power of wave-cliff impacts. Numerical modelling (XBeach-G) showed that under highly energetic wave conditions, i.e. those that occurred in the North Atlantic during winter 2013–2014, with Hs = 5.5 m (dissipative site) and 8 m (reflective site), the combination of greater wave height and steeper Beach at the reflective site led to amplified wave run-up, subjecting these cliffs to waves over 4 times as powerful as those impacting the cliffs at the dissipative site (39 kWm-1 compared with 9 kWm-1). This study highlighted the sensitivity of cliff erosion to extreme wave conditions, where the majority (over 90% of the annual value) of cliff-face erosion ensued during the winter. The significance of these short-term erosion rates in the context of long-term retreat illustrates the importance of incorporating short-term Beach and wave dynamics into geomorphological studies of coastal cliff change.
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The role of Beach Morphology on coastal cliff erosion under extreme waves
Earth Surface Processes and Landforms, 2018Co-Authors: Claire Earlie, Gerhard Masselink, Paul RussellAbstract:Erosion of hard-rock coastal cliffs is understood to be caused by a combination of both marine and sub-aerial processes. Beach Morphology, tidal elevation and significant wave heights, especially under extreme storm conditions, can lead to variability in wave energy flux to the cliff-toe. Wave and water level measurements in the nearshore under energetic conditions are difficult to obtain and in situ observations are rare. Here we use monthly cliff-face volume changes detected using terrestrial laser scanning alongside Beach morphological changes and modelled nearshore hydrodynamics to examine how exposed cliffs respond to changes in extreme wave conditions and Beach Morphology. The measurements cover the North Atlantic storms of 2013 to 2014 and consider two exposed stretches of coastline (Porthleven and Godrevy, UK) with contrasting Beach Morphology fronting the cliffs; a flat dissipative sandy Beach at Godrevy and a steep reflective gravel Beach at Porthleven. Beach slope and the elevation of the Beach-cliff junction were found to influence the frequency of cliff inundation and the power of wave-cliff impacts. Numerical modelling (XBeach-G) showed that under highly energetic wave conditions, i.e. those that occurred in the North Atlantic during winter 2013-2014, with H-s = 5.5 m (dissipative site) and 8 m (reflective site), the combination of greater wave height and steeper Beach at the reflective site led to amplified wave run-up, subjecting these cliffs to waves over four times as powerful as those impacting the cliffs at the dissipative site (39 kWm(-1) compared with 9 kWm(-1)). This study highlighted the sensitivity of cliff erosion to extreme wave conditions, where the majority (over 90% of the annual value) of cliff-face erosion ensued during the winter. The significance of these short-term erosion rates in the context of long-term retreat illustrates the importance of incorporating short-term Beach and wave dynamics into geomorphological studies of coastal cliff change. (C) 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley and Sons Ltd.
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Beach Morphological Predictions: The Impact of a Temporally Varying Sediment Fall Velocity
Journal of Coastal Research, 2016Co-Authors: Sam Prodger, Paul Russell, Mark Davidson, Jon MilesAbstract:ABSTRACT Prodger, S.; Russell, P.; Davidson, M., and Miles, J., 2016. Beach Morphological Predictions: The Impact of a Temporally Varying Sediment Fall Velocity In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 447–451. Coconut Creek (Florida), ISSN 0749-0208. This paper introduces new field measurements that allow quantification of the relative importance of temporal variations in grain size to Beach Morphology classification. A dataset of 7 years of daily remotely sensed Beach morphological measurements and monthly intertidal topographic surveys with surface sediment sampling were used to assess how observed temporal variations in sediment size (or fall velocity) influence morphological predictions at two energetic, sandy macro-tidal Beach sites. Beach morphological predictions were obtained via the widely used sequential classification scheme of ...
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test of edge wave forcing during formation of rhythmic Beach Morphology
Journal of Geophysical Research, 2004Co-Authors: Gerhard Masselink, Paul Russell, Giovanni Coco, D A HuntleyAbstract:[1] This paper reports on concurrent measurements of evolving rhythmic Beach Morphology and the associated water motion on a macrotidal, coarse sandy Beach. Beach cusps with a spacing of 19 m developed over a 3-day period of low-energy swell after which they were destroyed by energetic wind waves. The Beach cusps were clearly accretionary features and developed mainly during the rising tide. Detailed hydrodynamic measurements were conducted at three locations in the swash and inner surf zone in the vicinity of a developing cusp horn and revealed that energetic standing, mode-zero, subharmonic edge waves were not present during the initiation of the Beach cusps. Specifically, analysis of the hydrodynamic data indicated that: (1) the amount of subharmonic energy was limited (<10% of the total energy); (2) none of the computed energy spectra exhibited a significant peak at the subharmonic frequency; (3) the cross-shore velocity amplitude at the subharmonic frequency was 2–3 times larger than the longshore velocity amplitude; (4) the longshore current motion at the subharmonic frequency was barely coherent between adjacent locations in the surf zone; and (5) the time series of pressure and cross-shore current were in phase at either side of the developing cusp horn. It is concluded that, at least during this event of Beach cusp formation, energetic standing edge waves are not a prerequisite to initiate the development of rhythmic Beach Morphology.
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Test of edge wave forcing during formation of rhythmic Beach Morphology
Journal of Geophysical Research, 2004Co-Authors: Gerhard Masselink, Paul Russell, Giovanni Coco, D A HuntleyAbstract:[1] This paper reports on concurrent measurements of evolving rhythmic Beach Morphology and the associated water motion on a macrotidal, coarse sandy Beach. Beach cusps with a spacing of 19 m developed over a 3-day period of low-energy swell after which they were destroyed by energetic wind waves. The Beach cusps were clearly accretionary features and developed mainly during the rising tide. Detailed hydrodynamic measurements were conducted at three locations in the swash and inner surf zone in the vicinity of a developing cusp horn and revealed that energetic standing, mode-zero, subharmonic edge waves were not present during the initiation of the Beach cusps. Specifically, analysis of the hydrodynamic data indicated that: (1) the amount of subharmonic energy was limited (