Wales, United Kingdom
Wales, United Kingdom

Time filter

Source Type

Thomas T.,Carmarthenshire County Council | Phillips M.R.,University of Swansea | Williams A.T.,University of Swansea | Jenkins R.E.,University of Swansea
Applied Geography | Year: 2012

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 = 0.83), and longshore sediment distribution (r = 0.91). North Beach level variations lagged behind South Beach by one-year (r = 0.85). A reduction in high wind speed frequency, coincidental to spring tides, was correlated with falling South Beach levels (r = 0.87) and rising North Beach levels (r = -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 = 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 = 0.75). While NAO variations were linked to variations in South Beach morphology, it was insignificant on North Beach (r = -0.72 and -0.14 respectively). Cross-correlation analyses showed that North Beach morphological changes lagged behind NAO Index variation by one-year with much improved correlation (r = 0.77). A similar scenario existed when comparing Mean Sea level and beach level differences (r = -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 strategies. © 2011 Elsevier Ltd.


Thomas T.,Carmarthenshire County Council | Phillips M.R.,University of Swansea | Williams A.T.,University of Swansea | Jenkins R.E.,University of Swansea
Applied Geography | Year: 2012

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. © 2012 Elsevier Ltd.


Thomas T.,Carmarthenshire County Council | Phillips M.R.,University of Swansea | Williams A.T.,University of Swansea | Jenkins R.E.,University of Swansea
Progress in Physical Geography | Year: 2011

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 = -0.67), while cross-correlation at a one-month timelag increased statistical significance (r = 0.84). Due to beach aspect, gale wave heights decreased as wave direction rotated to the south (R2 = 0.4) and west (R2 = 0.65), while offshore wave direction influenced change at the southern and northern extremities (R2 = 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 (R2 = 0.69 and R2 = 0.72, 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 = 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. © The Author(s) 2011.


Thomas T.,Carmarthenshire County Council | Phillips M.R.,University of Swansea | Williams A.T.,University of Swansea | Jenkins R.E.,University of Swansea
Geomorphology | Year: 2011

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. © 2011 Elsevier B.V.


Thomas T.,Carmarthenshire County Council | Phillips M.R.,University of Swansea | Williams A.T.,University of Swansea
Journal of Coastal Research | Year: 2011

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.


Phillips M.R.,University of Swansea | Rees E.F.,University of Swansea | Thomas T.,Carmarthenshire County Council
Global and Planetary Change | Year: 2013

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, p<0.01 and tcalc=46.6, df=9, p<0.01 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±0.06knots/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. © 2012.


Thomas T.,Carmarthenshire County Council | Phillips M.R.,University of Swansea | Williams A.T.,University of Swansea | Jenkins R.E.,University of Swansea
Earth Surface Processes and Landforms | Year: 2014

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 7·5m). 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 © 2013 John Wiley & Sons, Ltd.


Thomas T.,Carmarthenshire County Council | Phillips M.R.,University of Swansea | Williams A.T.,University of Swansea
Journal of Coastal Research | Year: 2013

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. © Coastal Education & Research Foundation 2013.


Thomas T.,Carmarthenshire County Council | Phillips M.R.,University of Swansea | Williams A.T.,University of Swansea
Geomorphology | Year: 2010

The morphology change of a headland bay beach: Tenby, West Wales (GR 212200, 198599) has been analysed over a mesoscale timeframe (1830-2009). GIS, cross-shore profiles, off-shore wave climate, have been utilised to assess the role of atmospheric variability on long-term shoreline change. Previous studies have suggested that plan-form change seen in recent times has been caused by closure of Ritec valley estuary circa 1855, and whilst admittedly closure did have an initial effect with northerly dune field migration and reductions in inter-tidal and nearshore estuary flushing, this study suggests that climatic variations also contribute to evolution of this bay. Mesoscale analysis qualitatively highlights two distinct time periods of plan-form evolution characterised by total reversals in trend that take place around 1919. More recent bay rotation about a stable central sector, is shown quantitatively: the southern sector shows progressive retreat (R2=0.93), whilst the northern sector is shown to advance (R2=0.56). Points of rotation show steady migration northwards as retreat is encountered within the south sector (R2=0.79), which confirms that the bay is still evolving. On a decadal level, correlation can be found between positive NAO index values and beach level, and volume reductions based on a visually active beach profile (R2=0.44 and 0.53 respectively), whilst normalised wave height variability is also closely linked with index change (t=0.952, df=82, p>0.05) over a similar timeframe. Positive index values result in stormier south-westerly winds (180°-270°), where it is found that 54% of high winds emanate from this quadrant. Further correlation is found between these winds and NAO Index (R2=0.47). Winds from this direction produce waves that diffract and refract around Giltar headland and off-shore Caldey island, that induce a south to north movement of sediment increasing southerly shoreline retreat and, conversely, northerly advance. Qualitative observations of hind-casts produced using decadal analysis regression equations and mesoscale NAO data suggest that the atmospheric variation is a contributory factor in bay evolution. Similar scenarios are likely to exist at other locations; therefore, assessments should be repeated more widely, to develop appropriate management strategies. © 2010 Elsevier B.V.


Ng K.,University of The Azores | Phillips M.R.,University of Wales Trinity Saint David | Borges P.,University of The Azores | Thomas T.,Carmarthenshire County Council | And 3 more authors.
Science of the Total Environment | Year: 2014

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 socio-economic 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 São Miguel Island (the Azores SI archipelago) and considers SI issues with regard to coastal land loss. Regional wave statistics using 1998 to 2011 wind record showed: periods ranging from 7 to 13s (circa 83%); wave heights between 1 and 3m (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±0.4mmyr-1; p=0.000), while between 1996 and 2007 it was 3.3±1.5mmyr-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 1km 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. © 2014 Elsevier B.V.

Loading Carmarthenshire County Council collaborators
Loading Carmarthenshire County Council collaborators