The morphological change of a headland bay beach—Tenby, West Wales, UK—was analysed over a 73-yea... more The morphological change of a headland bay beach—Tenby, West Wales, UK—was analysed over a 73-year period (1941–2014). Geo-referenced aerial photographs were used to extract shoreline positions which were subsequently compared with wave models based on storm event data. From the 1941 baseline, results showed shoreline change rates reduced over time with regression models enabling a prediction of shoreline equilibrium circa 2061. Further temporal analyses showed southern and central sector erosion and northern accretion, while models identified long-term plan-form rotation, i.e., a negative phase relationship between beach extremities and a change from negative to positive correlation within the more stable central sector. Models were then used in conjunction with an empirical 2nd order polynomial equation to predict the 2061 longshore equilibrium shoreline position under current environmental conditions. Results agreed with previous regional research which showed that dominant south and southwesterly wave regimes influence south to north longshore drift with counter drift generated by less dominant easterly regimes. The equilibrium shoreline was also used to underpin flood and inundation assessments, identifying areas at risk and strategies to increase resilience. UK shoreline management plans evaluate coastal vulnerability based upon temporal epochs of 20, 50 and 100 years. Therefore, this research evaluating datasets spanning 73 years has demonstrated the effectiveness of linear regression in integrating temporal and spatial consequences of sea level rise and storms. The developed models can be used to predict future shoreline positions aligned with shoreline management plan epochs and inform embayed beach shoreline assessments at local, regional and international scales, by identifying locations of vulnerability and enabling the development of management strategies to improve resilience under scenarios of sea level rise and climate change.
This paper investigates potential climate-change impacts on the Outer Bristol Channel (Wales, U.K... more This paper investigates potential climate-change impacts on the Outer Bristol Channel (Wales, U.K.) by analysing a 15-year wave-buoy dataset (1998–2013) to characterise wave climate and storms. The research showed that the increasing storminess experienced during the latter half of the 20th century did not, as expected, continue into the first decades of the 21st century; however, the wave climate showed clear cyclic variation in average monthly significant wave height (Hs), with low values occurring between May and August (Hs , 1.4 m, Hsmax , 6 m) and a minimum in August (Hs ¼1.3 m, Hsmax¼5.2 m). Monthly mean wave power was 27.4 kwm1, with a maximum of 951 kwm1 during December. The 267 storm events were recorded during the assessment period. Storm-severity distribution presented a log-normal trend, with weak and moderate events making up 73% of the record (125 and 69 events, respectively); significant (18%), severe (4%), and extreme (6%) storms resulting in 73 events that are more destructive made up the remainder of the record. Fifty-five percent of the monthly averaged wave variations, wave power, and storminess indices are linked to several teleconnection patterns, the most relevant being the Arctic Oscillation, with 23.45%, the North Atlantic Oscillation, with 20.65%, and the East Atlantic with 10.9%. This kind of characterization is essential for design considerations to any proposed developments within the Bristol Channel that affect the coastal zone, e.g., the proposed design of the Swansea Bay Tidal Lagoon, which is capable of generating over 542,000 MWhyr1 of renewable energy.
Cross-shore profiles and environmental forcing were used to analyse morphological change of a hea... more Cross-shore profiles and environmental forcing were used to analyse morphological change of a headland bay beach: Tenby, West Wales (51.66 N; −4.71 W) over a mesoscale timeframe (1996–2013). Beach profile variations were attuned with longer term shoreline change identified by previous research showing southern erosion and northern accretion within the subaerial zone and were statistically significant in both sectors although centrally there was little or no significance. Conversely a statistically significant volume loss was shown at all profile locations within the intertidal zone. There were negative phase relationships between volume changes at the beach extremities, indicative of beach rotation and results were statistically significant (p < 0.01) within both subaerial (R 2 = 0.59) and intertidal (R 2 = 0.70) zones. This was confirmed qualitatively by time-series analysis and OPEN ACCESS J. Mar. Sci. Eng. 2015, 3 1007 further cross correlation analysis showed trend reversal time-lagged associations between sediment exchanges at either end of the beach. Wave height and storm events displayed summer/winter trends which explained longer term one directional rotation at this location. In line with previous regional research, environmental forcing suggests that imposed changes are influenced by variations in southwesterly wind regimes. Winter storms are generated by Atlantic southwesterly winds and cause a south toward north sediment exchange, while southeasterly conditions that cause a trend reversal are generally limited to the summer period when waves are less energetic. Natural and man-made embayed beaches are a common coastal feature and many experience shoreline changes, jeopardising protective and recreational beach functions. In order to facilitate effective and sustainable coastal zone management strategies, an understanding of the morphological variability of these systems is needed. Therefore, this macrotidal research dealing with rotational processes across the entire intertidal has significance for other macrotidal coastlines, especially with predicted climate change and sea level rise scenarios, to inform local, regional and national shoreline risk management strategies.
Beach Profiles surveys and gale climate data were utilised to assess medium timescale beach rotat... more Beach Profiles surveys and gale climate data were utilised to assess medium timescale beach rotation at four beaches located along the shores of a crenulated embayment within Swansea Bay, SouthwestWales. The proposed Tidal Lagoon is located within this Bay. Results identified a 7 year (1998e2005) record of cyclic summer/winter rotation and a 14 year (1999e2013) record of annual rotation within the subaerial zone on all four assessed beaches. In the absence of headlands to trap sediment it is asserted that the driving force for beach rotation is the presence of Swansea Dockland/Tawe dredged channel complex, Port Talbot Harbour and the Neath dredged channel which form surrogate headlands essentially creating four separate beach systems through restricting sediment by-pass. Seasonal averaged wind and wave variables showed differing correlation with volume changes and cross-correlation results showed that volume variation lagged behind forcing variables by up to six months (i.e. the resolution of the data). This was confirmed by the annually averaged results which showed only subtle correlation. Here volume change in most cases lagged forcing variables by less than one year. Based on correlations, wind direction variability follows closely with volume changes but wind speed, wave period and height are generally opposite. Initial results suggest that the proposed Swansea Bay Tidal Lagoon, located between sediment cells and surrogate headlands, would have little negative effect on subaerial coastal processes. These datasets will be used as a benchmark for monitoring prior
This work presents the analysis of fifteen years (1993 to 2007 inclusive) MetOffice wind data for... more This work presents the analysis of fifteen years (1993 to 2007 inclusive) MetOffice wind data for the Bristol Channel/Severn Estuary. Data from the Turbot Bank Buoy, located within the open waters of the Bristol Channel, showed significant reducing trends in monthly mean and maximum extreme wind speeds. Coupled with significant falling extreme sea level trends over the same time period, and direct correlation between wind speed and sea level, the increased storminess experienced during the latter half of the twentieth century seems not to have continued into the first decade of the twenty-first century. Wind speeds and directions between 1993 and 2002 inclusive at Turbot Bank Buoy were found to be significantly higher than those measured at the relatively nearby Rhoose land based station (Paired t test: tcalc=87.74, df=9, pb0.01 and tcalc=46.6, df=9, pb0.01 respectively). This highlights problems in using land based wind records to represent sea conditions, as well as using one location as representative of conditions along a coastline. Analysis further showed a small range of annual mean wind angles (circa 180° to 210° true). There was a significant regression between wind speed and NAO Index, given by 0.33±0.06 knots/NAO unit (p=0.000). This was more important during positive NAO phases, as wind speeds reduced during negative phases. Regression also indicated a direct positive relationship between NAO Index and wind direction (15.7±7.5°/NAO unit; p=0.05), where higher wind angles are linked to a rising NAO. Therefore, results have major implications for morphological response to wind (speed and direction), sea level (mean and extreme) and NAO Index (positive and negative). Conditions are unlikely to be unique to this coastline and it is suggested that similar analyses are replicated elsewhere to improve understanding and characterisation of uncertainty.
Profiles were analysed in conjunction with wave climate to assess offshore island influences on a... more Profiles were analysed in conjunction with wave climate to assess offshore island influences on an embayed beach at Tenby, Wales. Time series analyses showed medium and short-term beach oscillation, with volume exchanges between zones lagging by up to six months. Dominant southerly and southwesterly waves caused sub and low tidal longshore drift from south towards north, while less frequent southeasterly waves generated counter drift. Modelled inshore breaking waves had less energy than offshore ones and the former behaved differently between the low and high tidal zones (spring tidal range of 7 5 m). Variations in wave direction from directly behind the islands resulted in reduced wave heights and statistical analyses agreed with wave model results. These were correlated to morphological change and it was concluded that offshore islands change wave dynamics and modify the morphology of embayed beaches in their lee. Consequently, this work provides significant new insights into offshore island influences, shoreline behaviour and especially tidal setting
Cross-shore profiles and environmental forcing were used to analyse morphological change of a hea... more Cross-shore profiles and environmental forcing were used to analyse morphological change of a headland bay beach: Tenby, West Wales (51.66 N; −4.71 W) over a mesoscale timeframe (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013). Beach profile variations were attuned with longer term shoreline change identified by previous research showing southern erosion and northern accretion within the subaerial zone and were statistically significant in both sectors although centrally there was little or no significance. Conversely a statistically significant volume loss was shown at all profile locations within the intertidal zone. There were negative phase relationships between volume changes at the beach extremities, indicative of beach rotation and results were statistically significant (p < 0.01) within both subaerial (R 2 = 0.59) and intertidal (R 2 = 0.70) zones. This was confirmed qualitatively by OPEN ACCESS J. Mar. Sci. Eng. 2015, 3 2 time-series analysis and further cross correlation analysis showed trend reversal timelagged associations between sediment exchanges at either end of the beach. Wave height and storm events displayed summer/winter trends which explained longer term one directional rotation at this location. In line with previous regional research, environmental forcing suggests that imposed changes are influenced by variations in southwesterly wind regimes. Winter storms are generated by Atlantic southwesterly winds and cause a south toward north sediment exchange, while southeasterly conditions that cause a trend reversal are generally limited to the summer period when waves are less energetic. Natural and man-made embayed beaches are a common coastal feature and many experience shoreline changes, jeopardising protective and recreational beach functions. In order to facilitate effective and sustainable coastal zone management strategies, an understanding of the morphological variability of these systems is needed. Therefore, this macrotidal research dealing with rotational processes across the entire intertidal has significance for other macrotidal coastlines, especially with predicted climate change and sea level rise scenarios, to inform local, regional and national shoreline risk management strategies.
The UK Government was recently criticised for failing to fulfil its obligations under the Habitat... more The UK Government was recently criticised for failing to fulfil its obligations under the Habitats Directive in respect of designating protected areas for Harbour Porpoise Phocoena phocoena. At the centre of the discussion lay the stringent nature of the qualifying criteria for site selection. Concurrently, there is a growing support for marine renewable energy technologies; however the planning process is often hampered by inadequate marine data to enable appropriate siting or mitigation against potential ecological impacts. The Bristol Channel region's physical environment is a suitable source for the generation of marine renewable energy, and the world's first tidal lagoon will be sited in Swansea Bay. A 10 year dataset was collected, analysed and compared against the qualifying criteria for a Special Area of Conservation (SAC). Results revealed that a resident population of porpoise existed and density values of 0.58 hp km2 were comparable with other UK regions. While an insignificant calf adult ratio of 1:13 was recorded, breeding and nursery areas were identified. Analysis highlighted a number of hotspots of porpoise activity, suggesting that these areas are critical habitats, particularly for feeding and foraging. Such information will enable future marine renewable energy developers to select the most appropriate sites. It is argued that existing SAC qualifying criteria prevents recognition of critical habitats for the harbour porpoise and a case is made for an eastward extension of a proposed harbour SAC to include Swansea Bay and the south Gower coast. This paper demonstrates that cetacean data is sparse and even though this study has filled important knowledge gaps, there is still a need for further research. This research would enable both developers and planners to adequately and appropriately consider future marine renewable energy projects.
This paper investigates how the presence of offshore Islands influence the morphological behaviou... more This paper investigates how the presence of offshore Islands influence the morphological behaviour in a headland embayment Tenby, West Wales [GR 212200, 198599]. Beach profile surveys and offshore wave climate have been utilised for this assessment. The majority of gales (75%) emanate from the southeast to westerly direction. Here, analyses of gale wave direction showed that the offshore Islands give shelter. These effects decrease with wave rotation, the highest waves emanate from directly behind the Islands, and decrease in height with rotation irrespective of direction. Southeast shifts generate waves within the shorter (fetch limited) Bristol Channel, and during southwest shifts, there is an interaction with the updrift Pembrokeshire coastline. Wave diffraction has a considerable influence on South Beach behavioural patterns, as wave direction rotates. Moreover, southeast shifts give rise to dominate wave diffraction around the easternmost point of Caldey Island, under these offshore wave conditions a trend of rising volume within each beach region was observed. In contrast, westerly shifts gave rise to dominant diffraction around the Giltar headland itself, and a loss of protection given by the offshore Islands. Under these offshore wave conditions, lowering volumes in all beach regions was observed. It is accepted that more detailed studies of wave diffraction and refraction are required to fully understand their consequences on South Beach morphology. However, sheltering effects of natural protection that prevents direct arrival of wave energy, has implications for coastal zone management, and careful examination of these phenomena are required both over short and longer timescales.
Medium term (decadal) beach profile response to external forcing was assessed on two adjacent
emb... more Medium term (decadal) beach profile response to external forcing was assessed on two adjacent embayed beaches (North and South Sands) in Pembrokeshire, West Wales. Both have contrasting physical and geological characteristics: a headland bay backed by dunes and a constrained embayment backed by geological promontories, promenades, walls and rock revetments. Paired t-tests showed significant changes at all cross-shore profile locations (95% confidence), with south and north shores respectively exhibiting falling and rising beach levels. South to north sediment transport was revealed by volumetric variation (r ¼ 0.83), and longshore sediment distribution (r ¼ 0.91). North Beach level variations lagged behind South Beach by one-year (r ¼ 0.85). A reduction in high wind speed frequency, coincidental to spring tides, was correlated with falling South Beach levels (r ¼ 0.87) and rising North Beach levels (r ¼ 0.92). Heavily refracted Atlantic swells also have contrasting effects on these systems. Multiple regression models applied to beach level change for both systems showed high correlation (R2 ¼ 0.93 and 0.85 respectively), suggesting that swell wave period and strong north-westerly winds that occur during high spring tides had cumulative effects. Furthermore, variations in the North Atlantic Oscillation (NAO) index were correlated to cumulative changes in mean sea level, wind wave height and south-westerly winds (R2 ¼ 0.75). While NAO variations were linked to variations in South Beach morphology, it was insignificant on North Beach (r ¼ 0.72 and 0.14 respectively). Cross-correlation analyses showed that North Beach morphological changes lagged behind NAO Index variation by oneyear with much improved correlation (r ¼ 0.77). A similar scenario existed when comparing Mean Sea level and beach level differences (r ¼ 0.54 and 0.32 respectively). Similar behaviour should be exhibited at other worldwide embayments, and it is suggested that this work is repeated to establish specific responses, to will underpin intervention or no active intervention strategie
Aerial photographs, topographic field data and environmental forcing agents were used to assess h... more Aerial photographs, topographic field data and environmental forcing agents were used to assess historic and annual sand spit changes at Ginst Spit, Pendine Sands, West Wales. Aerial photographs highlighted that the spit shoreline facing the dominant wave direction had accreted steadily throughout the assessment timeframe (1947e2010). Stabilisation works in the form of rubble mounds aided recovery of the dune system thought to have been damaged due to training exercises carried out during the SecondWorld War. Annual topographic surveys (1995e2010) showed a terminal end eastward migration extending into the channel of the 3 estuary complex. Dominant waves emanate from south southwest, and wave models suggest that longshore sediment drift is from west toward east. Sub-dominant southeast waves create a counter drift back toward the west forming the customary northward hook. Model results showed significant wave transformation from offshore model boundaries to the nearshore zone for both wave height and direction, which found agreement with qualitative assessment. Annually averaged wave components showed varying correlations with sand spit rates of shoreline change. Precipitation and spit growth were associated with flood events, which suggested that a combination of fluvial and coastal processes contribute to lowland inundation. By showing the major role the spit plays in protecting the town in its lee, this work provides a new understanding of sand spit evolution to inform coastal management.
Traditional hard engineering structures and recently emerging soft engineering alternatives have ... more Traditional hard engineering structures and recently emerging soft engineering alternatives have been employed to protect vulnerable coastlines. Despite negative publicity, they have ensured community survival where socioeconomic benefits outweigh adverse impacts. This is especially true for Small Islands (SI) where increasing sea levels and storm intensities threaten already limited land availability. This paper presents coastal vulnerability in SãoMiguel Island (the Azores SI archipelago) and considers SI issueswith regard to coastal land loss. Regional wave statistics using 1998 to 2011wind record showed: periods ranging from7 to 13 s (circa 83%);wave heights between 1 and 3 m (circa 60%); and increasing trends in westerly (p= 0.473), easterly (p= 0.632) and southeasterly (p= 0.932) waves. Sea level analyses between 1978 and 2007 indicated a statistically significant rising trend (2.5 ± 0.4 mm yr−1; p = 0.000), while between 1996 and 2007 it was 3.3 ± 1.5 mm yr−1 (p = 0.025), agreeing with other global sea level studies. Based on 2001 and 2008 population data and using zonal statistics, circa 60% of the Island's population was found to reside within 1 km of the sea and the percentage of total population was linearly correlated with distance from the shoreline (r2 = 99%). Three case studies show hard coastal engineering solutions preserved Azorean coastal lifestyle and had little or no observed negative impacts on their environs. Although hard engineering is likely to remain a valuable and feasible coastal protection option, an inventory of São Miguel's population distribution, surf breaks, bathymetry and coastal erosion rates showed the potential of using multifunctional artificial reefs as a soft engineering solution. These offshore submerged breakwaters offer coastal protection while providing additional benefits such as surfing amenity and beach widening. Consequently, findings of this work can inform other SI communities.
Beach profiles, gale climate, atmospheric variations and wave models (RCPWave) were used to asses... more Beach profiles, gale climate, atmospheric variations and wave models (RCPWave) were used to assess beach rotation at two adjacent macrotidal open coast beaches, Pendine and Cefn Sidan Sands, West Wales. Results identified an 11 year record of rotation on both beaches where negative phase relationships were established between volume change at beach extremities within both subaerial and intertidal zones. In the absence of headlands to trap sediment, it is asserted that the driving force for beach rotation is the presence of two estuary complexes that act as surrogate headlands.Wave models found agreement with statistical analyses and showed that under dominant south-westerly waves, sediment movement is towards the estuary complexes, while subdominant south-easterly waves generate counter drift. This was supported by illustrations of sediment pathways for varying wave directions. NAO Index values change from positive to negative trends through time and were correlated to morphological change in both littoral settings. Beach volume change lagged NAO variation by six months at Pendine Sands and by up to two years at Cefn Sidan Sands, with opposing correlations observed at beach extremities. This suggests that rotation is caused by a reversal in NAO trends. These new findings are likely to be exhibited at other open coast locations and this work should be repeated elsewhere to inform coastal management strategies.
Using geographic information system (GIS) and field measurements the nearshore morphological vari... more Using geographic information system (GIS) and field measurements the nearshore morphological variability of a headland bay beach at Tenby, West Wales (51·66 N; –4·71 W) was assessed over historical timeframes (1748–2007). Three areas chosen for detailed analysis were the area between mean low water (MLW) and lowest astronomical tide (LAT) contours; LAT and one fathom contours; and one and two fathom contours. Estuary closure c. 1855 has been suggested as the genesis for long‐term beach evolution and did have an initial effect, with northward dune migration and reduced flushing effects. However, this research suggests nearshore bank migration and retrogradation associated with spit collapse took place prior to closure and continued throughout the assessed timeframe. Historical data revealed patterns of shoreward migration demonstrated by changes in orientation, Giltar headland acting as a pivot. Variations in sandbank position correlated with areal reduction of both Giltar spit and White Bank. Temporal offshore areal loss was contrasted against variable gains inshore as offshore banks welded to the beachface. Annual volumetric change analyses represented by profiles that extend 1 km offshore, confirmed Giltar spit and White Bank erosion rates of 91 m3 yr–1 and 458 m3 yr–1 respectively, and 220 m3 yr–1 beachface accretion. Diminution of sediment supply observed over historical timescales was supported by decadal evidence. Here, profile analysis revealed a trend of decreasing volumes both updrift and within the study area, and increasing downdrift volumes. This explained why proximal detachment and sediment redistribution had occurred. Distinct reversal’s in shoreline trend (rotation) corresponded to nearshore change; therefore, variations in seabed configuration triggered shoreface dynamic change over century timescales. Five‐year cumulative average changes in North Atlantic Oscillation were further correlated to this reversal. As comparable scenarios are likely to exist at other worldwide coastal locations, similar analyses should be incorporated into shoreline monitoring programmes. Consequently, these assessments would inform shoreline trends and support coastal management decisions.
Beach rotations are reliant on a bi-directional wave climate and headlands to impede alongshore s... more Beach rotations are reliant on a bi-directional wave climate and headlands to impede alongshore sediment transport. This manifests itself in localised shoreline retreat or advance but does not lead to long term sediment loss or gain, as beaches often return to initial conditions in response to wave direction shifts and these changes are often seasonal. This paper assesses morphological changes of a headland embayed beach (Tenby, West Wales) over a 180 year period using GIS, cross shore profiles, and wave modelling. Within GIS maps, aerial photographs and direct field measurements identified two significant changes in beach orientation between the periods 1830-1919 and 1919-2009. Analysis of more recent data (1941-2009) showed that a statistically significant (R2 = 64%) negative phase relationship existed between the beach extremities and correlation changes revealed central region rotation. Results were consistent with wave modeling (RCPWave) that showed dominant waves emanate from southwest and cause long term longshore drift from south toward north. Subdominant waves emanating from the southeast cause counter-drift. In the decadal and seasonal term, negative phase relationships indicative of beach rotation were also established. Cross-correlation analysis between beach extremities showed that decadal term rotation occurred at timescales of less than one year. This was verified by seasonal term results, which showed with increased statistical significance that sediment exchange between headlands takes up to two months. Results have implications for coastal zone management and careful examination of these phenomena is required over both seasonal and longer timescales and should be considered in the development of new beach management strategies.
Beach profile surveys, gale climate and atmospheric variations were utilized to assess medium tim... more Beach profile surveys, gale climate and atmospheric variations were utilized to assess medium timescale morphological change at South Sands, Tenby, West Wales. Due to beach aspect in relation to offshore islands, gale wave height decreased as wave direction rotated eastwards (r=0.83) and westwards (r=0.88). Similarly, wave heights were in attuned to variations in positive (r=0.68) and negative (r=−0.72) NAO Index, showing a wave height reduction occurred during weakly negative/positive or transitory phases; morphological change was attuned to atmospheric variation at a 2-year timelag. Shelter from offshore islands is given to waves from the predominant southwesterly direction and was confirmed by negligible correlation with South Sands morphology. However, outside the shelter of these offshore islands, correlation was found between south-eastward rotating wave directions (135°–180°) and morphological change, which resulted in southern and central beach erosion and accretion to the north. With a southwesterly rotation (243°–256°) the opposite was true. Beach rotation expressed by volume change within the sub-aerial zone had a negative phased relationship between beach extremities (r=−0.94) and a timelagged association within the intertidal zone (r=0.55). Analyses resulted in the development of two medium timescale rotation models based on incident wave direction and climatic variability. Results have global implications for headland bays in the lee of offshore islands, as well as macro-tidal beach areas; and consequently similar models could inform local, regional and national beach management strategies.
Beach profile surveys, offshore wave climate and variations in atmospheric conditions have been u... more Beach profile surveys, offshore wave climate and variations in atmospheric conditions have been utilized to assess a short-term beach rotation phenomenon in a headland embayment Tenby, West Wales. Beach rotation, expressed by subaerial volumetric change, was shown by a negative phase relationship between beach extremities (r ¼ –0.67), while cross-correlation at a one-month timelag increased statistical significance (r ¼ 0.84). Due to beach aspect, gale wave heights decreased as wave direction rotated to the south (R2 ¼ 0.4) and west (R2 ¼ 0.65), while offshore wave direction influenced change at the southern and northern extremities (R2 ¼ 0.52 and 0.34, respectively). Shelter from offshore islands and Giltar Headland contributes via wave diffraction to accretive, erosive and rotational patterns, and these are sensitive to variations around the predominant wave direction (229). A southerly shift induces north/south sediment movement, as waves diffract around the offshore islands, while a westerly change results in south/north sediment movement (i.e. beach rotation), as diffracted wave domination transfers to the headland. A general gale wave height reduction occurred when the North Atlantic Oscillation (NAO) was weak or in a transitional phase between positive or negative phases (R2¼0.69 and R2¼0.72, respectively). Morphological change was also attuned to atmospheric variation where a reversal in beach rotation was influenced by variations in positive and negative NAO/volume correlations and longshore profile location (R2 ¼ 0.54 and 0.69, respectively). The results of this study have wider implications for coastal management; it is suggested that models developed in similar systems elsewhere will form the basis of human intervention or no active intervention strategies.
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Papers by Tony Thomas
four beaches located along the shores of a crenulated embayment within Swansea Bay, SouthwestWales.
The proposed Tidal Lagoon is located within this Bay. Results identified a 7 year (1998e2005) record of
cyclic summer/winter rotation and a 14 year (1999e2013) record of annual rotation within the subaerial
zone on all four assessed beaches. In the absence of headlands to trap sediment it is asserted that the
driving force for beach rotation is the presence of Swansea Dockland/Tawe dredged channel complex,
Port Talbot Harbour and the Neath dredged channel which form surrogate headlands essentially creating
four separate beach systems through restricting sediment by-pass. Seasonal averaged wind and wave
variables showed differing correlation with volume changes and cross-correlation results showed that
volume variation lagged behind forcing variables by up to six months (i.e. the resolution of the data). This
was confirmed by the annually averaged results which showed only subtle correlation. Here volume
change in most cases lagged forcing variables by less than one year. Based on correlations, wind direction
variability follows closely with volume changes but wind speed, wave period and height are generally
opposite. Initial results suggest that the proposed Swansea Bay Tidal Lagoon, located between sediment
cells and surrogate headlands, would have little negative effect on subaerial coastal processes. These
datasets will be used as a benchmark for monitoring prior
Channel/Severn Estuary. Data from the Turbot Bank Buoy, located within the open waters of the Bristol Channel,
showed significant reducing trends in monthly mean and maximum extreme wind speeds. Coupled with
significant falling extreme sea level trends over the same time period, and direct correlation between wind
speed and sea level, the increased storminess experienced during the latter half of the twentieth century
seems not to have continued into the first decade of the twenty-first century. Wind speeds and directions between
1993 and 2002 inclusive at Turbot Bank Buoy were found to be significantly higher than those measured
at the relatively nearby Rhoose land based station (Paired t test: tcalc=87.74, df=9, pb0.01 and
tcalc=46.6, df=9, pb0.01 respectively). This highlights problems in using land based wind records to represent
sea conditions, as well as using one location as representative of conditions along a coastline. Analysis
further showed a small range of annual mean wind angles (circa 180° to 210° true). There was a significant
regression between wind speed and NAO Index, given by 0.33±0.06 knots/NAO unit (p=0.000). This was
more important during positive NAO phases, as wind speeds reduced during negative phases. Regression
also indicated a direct positive relationship between NAO Index and wind direction (15.7±7.5°/NAO unit;
p=0.05), where higher wind angles are linked to a rising NAO. Therefore, results have major implications
for morphological response to wind (speed and direction), sea level (mean and extreme) and NAO Index
(positive and negative). Conditions are unlikely to be unique to this coastline and it is suggested that similar
analyses are replicated elsewhere to improve understanding and characterisation of uncertainty.
Tenby, Wales. Time series analyses showed medium and short-term beach oscillation, with volume exchanges between zones
lagging by up to six months. Dominant southerly and southwesterly waves caused sub and low tidal longshore drift from south
towards north, while less frequent southeasterly waves generated counter drift. Modelled inshore breaking waves had less energy
than offshore ones and the former behaved differently between the low and high tidal zones (spring tidal range of 7 5 m). Variations
in wave direction from directly behind the islands resulted in reduced wave heights and statistical analyses agreed with wave model
results. These were correlated to morphological change and it was concluded that offshore islands change wave dynamics and
modify the morphology of embayed beaches in their lee. Consequently, this work provides significant new insights into offshore
island influences, shoreline behaviour and especially tidal setting
in respect of designating protected areas for Harbour Porpoise Phocoena phocoena. At the centre of the
discussion lay the stringent nature of the qualifying criteria for site selection. Concurrently, there is a
growing support for marine renewable energy technologies; however the planning process is often
hampered by inadequate marine data to enable appropriate siting or mitigation against potential
ecological impacts. The Bristol Channel region's physical environment is a suitable source for the generation
of marine renewable energy, and the world's first tidal lagoon will be sited in Swansea Bay. A 10
year dataset was collected, analysed and compared against the qualifying criteria for a Special Area of
Conservation (SAC). Results revealed that a resident population of porpoise existed and density values of
0.58 hp km2 were comparable with other UK regions. While an insignificant calf adult ratio of 1:13 was
recorded, breeding and nursery areas were identified. Analysis highlighted a number of hotspots of
porpoise activity, suggesting that these areas are critical habitats, particularly for feeding and foraging.
Such information will enable future marine renewable energy developers to select the most appropriate
sites. It is argued that existing SAC qualifying criteria prevents recognition of critical habitats for the
harbour porpoise and a case is made for an eastward extension of a proposed harbour SAC to include
Swansea Bay and the south Gower coast. This paper demonstrates that cetacean data is sparse and even
though this study has filled important knowledge gaps, there is still a need for further research. This
research would enable both developers and planners to adequately and appropriately consider future
marine renewable energy projects.
headland embayment Tenby, West Wales [GR 212200, 198599]. Beach profile surveys and offshore wave
climate have been utilised for this assessment. The majority of gales (75%) emanate from the southeast to
westerly direction. Here, analyses of gale wave direction showed that the offshore Islands give shelter. These
effects decrease with wave rotation, the highest waves emanate from directly behind the Islands, and decrease in
height with rotation irrespective of direction. Southeast shifts generate waves within the shorter (fetch limited)
Bristol Channel, and during southwest shifts, there is an interaction with the updrift Pembrokeshire coastline.
Wave diffraction has a considerable influence on South Beach behavioural patterns, as wave direction rotates.
Moreover, southeast shifts give rise to dominate wave diffraction around the easternmost point of Caldey Island,
under these offshore wave conditions a trend of rising volume within each beach region was observed. In
contrast, westerly shifts gave rise to dominant diffraction around the Giltar headland itself, and a loss of
protection given by the offshore Islands. Under these offshore wave conditions, lowering volumes in all beach
regions was observed. It is accepted that more detailed studies of wave diffraction and refraction are required to
fully understand their consequences on South Beach morphology. However, sheltering effects of natural
protection that prevents direct arrival of wave energy, has implications for coastal zone management, and careful
examination of these phenomena are required both over short and longer timescales.
embayed beaches (North and South Sands) in Pembrokeshire, West Wales. Both have contrasting
physical and geological characteristics: a headland bay backed by dunes and a constrained embayment
backed by geological promontories, promenades, walls and rock revetments. Paired t-tests showed
significant changes at all cross-shore profile locations (95% confidence), with south and north shores
respectively exhibiting falling and rising beach levels. South to north sediment transport was revealed by
volumetric variation (r ¼ 0.83), and longshore sediment distribution (r ¼ 0.91). North Beach level
variations lagged behind South Beach by one-year (r ¼ 0.85). A reduction in high wind speed frequency,
coincidental to spring tides, was correlated with falling South Beach levels (r ¼ 0.87) and rising North
Beach levels (r ¼ 0.92). Heavily refracted Atlantic swells also have contrasting effects on these systems.
Multiple regression models applied to beach level change for both systems showed high correlation
(R2 ¼ 0.93 and 0.85 respectively), suggesting that swell wave period and strong north-westerly winds
that occur during high spring tides had cumulative effects. Furthermore, variations in the North Atlantic
Oscillation (NAO) index were correlated to cumulative changes in mean sea level, wind wave height and
south-westerly winds (R2 ¼ 0.75). While NAO variations were linked to variations in South Beach
morphology, it was insignificant on North Beach (r ¼ 0.72 and 0.14 respectively). Cross-correlation
analyses showed that North Beach morphological changes lagged behind NAO Index variation by oneyear
with much improved correlation (r ¼ 0.77). A similar scenario existed when comparing Mean Sea
level and beach level differences (r ¼ 0.54 and 0.32 respectively). Similar behaviour should be
exhibited at other worldwide embayments, and it is suggested that this work is repeated to establish
specific responses, to will underpin intervention or no active intervention strategie
and annual sand spit changes at Ginst Spit, Pendine Sands, West Wales. Aerial photographs highlighted
that the spit shoreline facing the dominant wave direction had accreted steadily throughout the assessment
timeframe (1947e2010). Stabilisation works in the form of rubble mounds aided recovery of the
dune system thought to have been damaged due to training exercises carried out during the SecondWorld
War. Annual topographic surveys (1995e2010) showed a terminal end eastward migration extending into
the channel of the 3 estuary complex. Dominant waves emanate from south southwest, and wave models
suggest that longshore sediment drift is from west toward east. Sub-dominant southeast waves create a
counter drift back toward the west forming the customary northward hook. Model results showed significant
wave transformation from offshore model boundaries to the nearshore zone for both wave height
and direction, which found agreement with qualitative assessment. Annually averaged wave components
showed varying correlations with sand spit rates of shoreline change. Precipitation and spit growth were
associated with flood events, which suggested that a combination of fluvial and coastal processes
contribute to lowland inundation. By showing the major role the spit plays in protecting the town in its
lee, this work provides a new understanding of sand spit evolution to inform coastal management.
to protect vulnerable coastlines. Despite negative publicity, they have ensured community survival where socioeconomic
benefits outweigh adverse impacts. This is especially true for Small Islands (SI) where increasing sea
levels and storm intensities threaten already limited land availability. This paper presents coastal vulnerability
in SãoMiguel Island (the Azores SI archipelago) and considers SI issueswith regard to coastal land loss. Regional
wave statistics using 1998 to 2011wind record showed: periods ranging from7 to 13 s (circa 83%);wave heights
between 1 and 3 m (circa 60%); and increasing trends in westerly (p= 0.473), easterly (p= 0.632) and southeasterly
(p= 0.932) waves. Sea level analyses between 1978 and 2007 indicated a statistically significant rising
trend (2.5 ± 0.4 mm yr−1; p = 0.000), while between 1996 and 2007 it was 3.3 ± 1.5 mm yr−1 (p = 0.025),
agreeing with other global sea level studies. Based on 2001 and 2008 population data and using zonal statistics,
circa 60% of the Island's population was found to reside within 1 km of the sea and the percentage of total
population was linearly correlated with distance from the shoreline (r2 = 99%). Three case studies show hard
coastal engineering solutions preserved Azorean coastal lifestyle and had little or no observed negative impacts
on their environs. Although hard engineering is likely to remain a valuable and feasible coastal protection option,
an inventory of São Miguel's population distribution, surf breaks, bathymetry and coastal erosion rates showed
the potential of using multifunctional artificial reefs as a soft engineering solution. These offshore submerged
breakwaters offer coastal protection while providing additional benefits such as surfing amenity and beach
widening. Consequently, findings of this work can inform other SI communities.
beach rotation at two adjacent macrotidal open coast beaches, Pendine and Cefn Sidan Sands, West
Wales. Results identified an 11 year record of rotation on both beaches where negative phase relationships
were established between volume change at beach extremities within both subaerial and intertidal
zones. In the absence of headlands to trap sediment, it is asserted that the driving force for beach rotation
is the presence of two estuary complexes that act as surrogate headlands.Wave models found agreement
with statistical analyses and showed that under dominant south-westerly waves, sediment movement is
towards the estuary complexes, while subdominant south-easterly waves generate counter drift. This
was supported by illustrations of sediment pathways for varying wave directions. NAO Index values
change from positive to negative trends through time and were correlated to morphological change in
both littoral settings. Beach volume change lagged NAO variation by six months at Pendine Sands and by
up to two years at Cefn Sidan Sands, with opposing correlations observed at beach extremities. This
suggests that rotation is caused by a reversal in NAO trends. These new findings are likely to be exhibited
at other open coast locations and this work should be repeated elsewhere to inform coastal management
strategies.
headland bay beach at Tenby, West Wales (51·66 N; –4·71 W) was assessed over historical timeframes (1748–2007). Three areas
chosen for detailed analysis were the area between mean low water (MLW) and lowest astronomical tide (LAT) contours; LAT and
one fathom contours; and one and two fathom contours. Estuary closure c. 1855 has been suggested as the genesis for long‐term
beach evolution and did have an initial effect, with northward dune migration and reduced flushing effects. However, this research
suggests nearshore bank migration and retrogradation associated with spit collapse took place prior to closure and continued
throughout the assessed timeframe. Historical data revealed patterns of shoreward migration demonstrated by changes in
orientation, Giltar headland acting as a pivot. Variations in sandbank position correlated with areal reduction of both Giltar spit and
White Bank. Temporal offshore areal loss was contrasted against variable gains inshore as offshore banks welded to the beachface.
Annual volumetric change analyses represented by profiles that extend 1 km offshore, confirmed Giltar spit and White Bank erosion
rates of 91 m3 yr–1 and 458 m3 yr–1 respectively, and 220 m3 yr–1 beachface accretion. Diminution of sediment supply observed over
historical timescales was supported by decadal evidence. Here, profile analysis revealed a trend of decreasing volumes both updrift
and within the study area, and increasing downdrift volumes. This explained why proximal detachment and sediment redistribution
had occurred. Distinct reversal’s in shoreline trend (rotation) corresponded to nearshore change; therefore, variations in seabed
configuration triggered shoreface dynamic change over century timescales. Five‐year cumulative average changes in North Atlantic
Oscillation were further correlated to this reversal. As comparable scenarios are likely to exist at other worldwide coastal locations,
similar analyses should be incorporated into shoreline monitoring programmes. Consequently, these assessments would inform
shoreline trends and support coastal management decisions.
morphological change at South Sands, Tenby, West Wales. Due to beach aspect in relation to offshore islands,
gale wave height decreased as wave direction rotated eastwards (r=0.83) and westwards (r=0.88). Similarly,
wave heights were in attuned to variations in positive (r=0.68) and negative (r=−0.72) NAO
Index, showing a wave height reduction occurred during weakly negative/positive or transitory phases; morphological
change was attuned to atmospheric variation at a 2-year timelag. Shelter from offshore islands is
given to waves from the predominant southwesterly direction and was confirmed by negligible correlation
with South Sands morphology. However, outside the shelter of these offshore islands, correlation was
found between south-eastward rotating wave directions (135°–180°) and morphological change, which
resulted in southern and central beach erosion and accretion to the north. With a southwesterly rotation
(243°–256°) the opposite was true. Beach rotation expressed by volume change within the sub-aerial zone
had a negative phased relationship between beach extremities (r=−0.94) and a timelagged association
within the intertidal zone (r=0.55). Analyses resulted in the development of two medium timescale rotation
models based on incident wave direction and climatic variability. Results have global implications for headland
bays in the lee of offshore islands, as well as macro-tidal beach areas; and consequently similar models
could inform local, regional and national beach management strategies.
assess a short-term beach rotation phenomenon in a headland embayment Tenby, West Wales. Beach rotation,
expressed by subaerial volumetric change, was shown by a negative phase relationship between beach
extremities (r ¼ –0.67), while cross-correlation at a one-month timelag increased statistical significance
(r ¼ 0.84). Due to beach aspect, gale wave heights decreased as wave direction rotated to the south
(R2 ¼ 0.4) and west (R2 ¼ 0.65), while offshore wave direction influenced change at the southern and northern
extremities (R2 ¼ 0.52 and 0.34, respectively). Shelter from offshore islands and Giltar Headland contributes
via wave diffraction to accretive, erosive and rotational patterns, and these are sensitive to variations
around the predominant wave direction (229). A southerly shift induces north/south sediment movement,
as waves diffract around the offshore islands, while a westerly change results in south/north sediment movement
(i.e. beach rotation), as diffracted wave domination transfers to the headland. A general gale wave height
reduction occurred when the North Atlantic Oscillation (NAO) was weak or in a transitional phase between
positive or negative phases (R2¼0.69 and R2¼0.72, respectively). Morphological change was also attuned to
atmospheric variation where a reversal in beach rotation was influenced by variations in positive and negative
NAO/volume correlations and longshore profile location (R2 ¼ 0.54 and 0.69, respectively). The results of
this study have wider implications for coastal management; it is suggested that models developed in similar
systems elsewhere will form the basis of human intervention or no active intervention strategies.