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Abstract: State-of-the-art morphodynamic field data were collected from Slapton Sands (UK), a fine-gravel beach (D 50 =2–10mm), over a 10-day period under a range of wave–tide conditions, comprising a mixture of southerly swell and easterly wind waves (H s =0.5–1m; T s =4–8s; tide range=3–4m). Over the field period, the upper beach experienced accretion and berm formation during tides with low steepness, swell-dominated wave conditions (H/L <0.01), and underwent erosion during tides dominated by high steepness wind waves (H/L >0.01). Surprisingly, the intertidal beach showed an opposite trend with sediment losses under swell conditions and an increase in sediment volume due to wind waves, and suggests that upper beach morphological change can be decoupled from the overall sediment budget. A submerged accretionary feature (the beach step) grew and migrated onshore on the rising tide, typically reaching a maximum relief of around 0.5m, then gradually decreased in prominence while migrating offshore as the tide fell, resulting in little net morphological change. The step was better developed during the falling tide than the rising tide and, through its control on the swash hydro- and sediment dynamics, the step had a significant effect on the development of the berm. Swash flow velocities under the conditions measured were often in excess of 2ms−1 for both the uprush and the backwash. Onshore mean flows occurred in the upper swash region (<40% inundation), while the lower swash region (>40% inundation) was characterised by offshore mean flows. Swash infiltration losses in the swash zone increased from 40% in the lower swash region to 100% in the upper swash region. The most energetic swash flows and the strongest offshore mean flows occurred at the transition between swash zone and surf zone (90–100% inundation). [Copyright &y& Elsevier]

Beach water users such as bathers and surfers are of economic importance to tourism in Cornwall, UK. Wave energy converters soon to be trialed at the 'Wave Hub' marine renewables test site in Cornwall, may reduce inshore wave heights and have an unknown effect on wave period, therefore potentially affecting water recreation and tourism on the beaches in its lee. There is little existing research to indicate what surf conditions are 'preferred' by various beach water user groups, and how they perceive different wave conditions has never been investigated. Without an understanding of how waves are observed and described by water users, little can be said about how likely they are to be affected by, or if they will correctly perceive, any changes to inshore waves caused by Wave Hub or future renewables projects. To investigate how waves are perceived, nearshore wave buoy measurements collected in 10 m water depth and transformed to breaking height, were compared to concurrent visual observations of mean breaker height and period made by 354 participants. Ratios of observed over measured height and period were used to quantify the perceptions. The vast majority of water users underestimated significant wave height and period at breaking, and their average perceptions can be approximated by Hvis ≈ 0.70Hb and Tvis ≈ 0.83T1/3 (for waves 0.5 ≤ Hb ≤ 3.5 m and 3 ≤ T1/3 ≤ 15 s). Although perceptions were highly varied, average perceptions did not change significantly under different wave conditions. Perception of wave period did not change significantly between the different water user groups considered. Expert water users and surfers generally under predicted wave height the most, especially for small and/or short period waves, while novices and non-surfing water users made height observations closer to measurements. [ABSTRACT FROM AUTHOR]

Abstract: Spatial data collected over three years are presented to assess the extent of morphological variability under seasonal and storm waves on two high-energy macrotidal beaches on the north Cornish coast. Of particular interest was the degree to which the beaches displayed bar/rip morphology and a novel approach to quantify the three-dimensionality of the beach based on the curvature of the bottom contours is adopted to identify and classify the three-dimensional beach response to changes in the dominant forcing conditions. Morphologically, the beaches range from dissipative to intermediate and are characterised by low tide bar/rip morphology which plays a key role in the nearshore dynamics and beach safety. Real-time kinematic (RTK) GPS surveys were undertaken using an all-terrain vehicle to measure the three dimensional (3D) morphology. In addition, nearshore wave data, in-situ hydrodynamic measurements, local tide gauges and Argus video data allowed detailed analysis of process–response mechanisms for long term (yearly); seasonal (monthly); storm (weekly/daily); and tidal (hourly) morphological behaviour. Both sites exhibited net long term accretion derived from the intertidal beach volume. Throughout the survey period, inter-site similarity in beach response was observed in response to storm waves, yet coupling between the seasonal wave climate and the beach morphology was not evident at either of the sites. Increased wave conditions (exceeding Hs =4m) during sustained storm events (>50h) led to offshore transport from the beachface to the subtidal bar region. Post-storm recovery was characterised by onshore transport and the development of substantial 3D low tide morphology. Under normal wave conditions (Hs =1.6m), the dominant 3D features smoothed out as channels in-filled and bar prominence reduced over a period of 2–3months. Overall, the beaches exhibited a significant storm-dominated morphological response cycle, unlike the more familiar winter/summer seasonal response. [Copyright &y& Elsevier]

Abstract: The use of beach classification models has become widespread in literature in recent years. Beach classification models that recognise distinct modal beach states in response to environmental conditions are most widely used. These models were developed largely in high-energy, micro- to meso-tidal sandy environments and subsequent attention has focussed on extending their use into other beach environments. Here, the applicability of these traditional beach classification models to the highly diverse coastline of England and Wales was assessed through collection of detailed morphodynamic characteristics of 92 beaches, yielding a comprehensive multi-variate data set containing morphological, sedimentological and hydrodynamic information. The complex and diverse study region incorporates beach morphology covering the full spectrum from reflective to dissipative, and non-barred to multi-barred. Cluster analysis supplemented by MDS ordination resulted in the identification of 9 distinct beach types. Traditional morphodynamic indices Ω and RTR were found to be effective in discriminating between beach groups providing some support for the beach state models derived using information from Australian beaches. It was found that absolute wave energy (wave power) is important as well in controlling beach type. For intermediate beaches a wave energy flux P (∝ H 2 T) value of 3kWm−1 was found to differentiate between beaches with (P >3kWm−1) and without (P <3kWm−1) three-dimensional bar/rip morphology, a key component controlling recreational beach hazard levels. Observations presented here inform a beach classification model to be used as the basis for a national beach risk assessment programme. Beach classification models based on environmental parameters are, by necessity, simplifications and should be used as tools for understanding morphodynamic systems, rather than beach type prediction. [Copyright &y& Elsevier]

Sand and gravel beaches naturally act as a coastal buffer, absorbing wave energy and dynamically adapting to the seasonal and long-term wave climate. Significant shifts in nearshore morphology can occur during extreme wave events, which can have a significant impact on coastal vulnerability. During the winter of 2013/14, the Atlantic coast of Europe received an unprecedented sequence of very energetic wave conditions (8-week mean offshore H s = 4.4 m). These events caused extensive physical (beach and dune erosion) and socio-economic (flooding, damage to infrastructure) impacts throughout the west coast of Europe. Many monitored sites in the UK and France were in their most eroded state since morphological records began (5–10 years). We consider the geomorphological significance of the storm response at 38 natural beaches in the southwest of England, ranging from semi-sheltered reflective gravel barriers to ultra-dissipative exposed sand beaches with dunes. The extent and patterns of post-storm recovery are examined in detail at three beaches with characteristic storm response behaviours. Exposed sandy beaches were dominated by cross-shore transport processes leading to significant loss of sediment offshore from the intertidal zone (> 200 m 3 /m); exposed gravel beaches were dominated by overwash with significant loss landward; and semi-sheltered sites exposed to more oblique wave forcing were dominated by a rotational response due to alongshore sediment redistribution. Due to these contrasting responses, mechanisms and timescales for beach recovery displayed strong inter-site and intra-site variations. In offshore and rotational cases, the recovery processes were multi-annual, comprising seasonal to decadal signals and were intrinsically linked to the storm response mechanisms, while permanent losses occurred when overwash dominated. We show that post-storm recovery does not necessarily occur during calm periods and that in many cases high-energy wave events appear to be essential for recovery of sediment (offshore and counter-rotation). Our results highlight the significance of dominant climatic oscillations, multi-annual storm sequencing, storm tracks and resultant variations in wave angle, in controlling the impact that extreme wave events have on contrasting sand/gravel beaches in exposed/sheltered locations. [ABSTRACT FROM AUTHOR]