Surf zones of sandy beaches are among the most heavily impacted aquatic ecosystems, yet are of critical ecological importance for inshore fish and fisheries. Knowledge of the drivers of fish habitat use in surf zones is needed across broad scales to advise conservation and fisheries management, but sampling capabilities can be limited in spatio-temporal extent and resolution. The lesser weever Echiichthys vipera a is a small, benthic, venomous fish that dominates surf zone fish assemblages in Northwest Europe and inflicts painful stings on beachgoers. This study capitalises on an extensive record of E. vipera sting incidents to characterise variations in surf zone habitat use in relation to key physical environmental factors. Sting incidents, standardised by water user numbers, are used as a proxy for E. vipera abundance across 77 beaches throughout Southwest England, with 2 h resolution, from April-November 2018. General Additive Models indicated a clear peak in E. vipera abundance at spring low tides, in the afternoons of summer months, under calmer wave conditions and at higher levels of solar irradiance. Although the order of significance differed, human water users were also driven by the same variables, compounding sting interactions over time. Key physical variables did not explain spatial variation in E. vipera abundance, although there was a weak relationship with sea surface temperature, and some evidence that reflective beaches are unsuitable. Physical factors explained more spatial variation in human water users, who gathered at more dissipative beaches with greater wave heights. This detailed study of an important surf zone fish reveals clear drivers of temporal variation in habitat use, yet infers wide suitability of beaches varying in the key physical drivers of sandy shore ecology.

Sediments play a key role in determining beach slope, transport rates and morphodynamic behaviour. Beach sediment characteristics, such as grain size and sorting, are known to vary spatially, both across the profile and alongshore and temporally in response to erosion and accretion events. Are these spatial and temporal changes systematic and predictable, or more random? To answer this question, this contribution uses an unprecedented 8-year record of surface sediment samples with interand sub-tidal topographic surveys, supplemented by spatially dense digital grain size surveys, sand cores (up to 1 m), subtidal grab samples, remote video observations and inshore hydrodynamic measurements. The data is from 53 beaches round the south-west peninsula of the UK covering a wide range of sediments sizes and wave exposures, with more detailed analysis from a typical oceanic high-energy sandy beach (Perranporth). Three consistent trends were found, i) sediments became coarser and better sorted with increasing distance across the intertidal zone, ii) sediments became coarser and better sorted with increasing depth below the bed and iii) sediments became finer and poorer sorted with increasing offshore distance from mean low water springs. A conceptual model is proposed that systematically relates changes in sediment size and sorting to cycles of beach erosion and accretion. During persistent periods of high steepness waves the intertidal beach erodes and finer sediments are carried offshore resulting in the intertidal surface sediments 308 becoming coarser and better sorted and the subtidal sediments becoming finer and more poorly sorted. During persistent periods of low steepness waves, the reverse occurs, with the finer sediment fractions being transported onshore to the intertidal beach so that intertidal surface sediments become finer and more poorly sorted.

Grain size and sorting represent two key parameters when characterizing sediments or modelling beach morphology and sediment transport. Traditionally, an average value for grain size or sorting is often assumed for the entire area, determined from only a few sediment samples, ignoring any spatial (or temporal) variability in sediment characteristics. This contribution uses a data set of physical surface sediment samples from 53 beach locations around the south‐west peninsula of the United Kingdom, in addition to bi‐monthly, high spatial resolution (mean 240 samples) digital grain‐size surveys from a high‐energy, oceanic, sandy beach (Perranporth, North Cornwall). Systematic spatial variations in grain size and sorting were consistently observed in the seaward direction across the intertidal zone of sandy beaches, with grain‐sizes coarsening and sorting improving by up to 51·7% and 64·3%, respectively. This variability was deterministically related to the time‐averaged, antecedent‐adjusted energy dissipated by breaking waves, with the observed maximum grain‐size and sorting values correlating with the location of peak wave energy dissipation ( r 2 = 0·998, P < 0·01).

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 Masselink and Short (1993), where time varying wave height and wave period are usually used to drive changes in beach state. Beach state was found to be highly seasonal, with an evolution from more dissipative states in the winter to lower intermediate states in the summer. Beach state predictions were made using both a constant and time-varying sediment fall velocity and then compared to visual observations of morphological state. Predictions using a constant fall velocity correlated poorly (r2 = 0.32) with observations, whereas predictions made using a time-varying fall velocity, correlated better (r2 = 0.79). A feedback loop was also evident in the system, with energetic waves promoting a migration towards a dissipative state, and a coarsening shoreface grain size.

Despite representing a key parameter when modelling morphology or sediment transport, surface sediments are often assumed homogenous, with grain size temporally constant. This contribution uses a 6-year data set of monthly sediment samples to quantify the observed variability in intertidal beach sands at four energetic, macrotidal locations (North Cornwall, UK). Changes in grain size and sorting were related to periods of high-steepness storm waves promoting a relatively rapid coarsening and an improvement in sorting and low-steepness swell waves, a fining and a reduction in sorting. These temporal changes in intertidal grain size were coherently linked to the disequilibrium in wave steepness, with peak coarsening occurring when the instantaneous wave steepness conditions vastly exceeded a temporally evolving antecedent time series. Using this concept, a simple model is proposed that provides skilful predictions of the unseen variability in sediment grain size (average r2=0.86, p<0.01) and sorting (average r2=0.75, p<0.05), at all four sites.

Coastal Sediments 2015 (2015) No AccessGRAIN SIZE VARIABILITY ON HIGH-ENERGY MACROTIDAL BEACHESSAM PRODGER, PAUL RUSSELL, MARK DAVIDSON, and JON MILESSAM PRODGERSchool of Marine Science & Engineering, Plymouth University, Plymouth, PL4 8AA, UK, PAUL RUSSELLSchool of Marine Science & Engineering, Plymouth University, Plymouth, PL4 8AA, UK, MARK DAVIDSONSchool of Marine Science & Engineering, Plymouth University, Plymouth, PL4 8AA, UK, and JON MILESSchool of Marine Science & Engineering, Plymouth University, Plymouth, PL4 8AA, UKhttps://doi.org/10.1142/9789814689977_0059Cited by:0 (Source: Crossref) PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: Temporal and spatial variability of beach sediment grain size was studied using 48 beach sites around the southwest peninsula of England. Highenergy beaches on the north coast exposed to the prevailing waves were found to be composed of medium quartz sand, whilst more sheltered south coast beaches were predominantly coarse sand to medium gravel. At all beach sites, sediment cores showed a general coarsening with depth over the top metre of the sediment column. For two adjacent north coast beaches sediment grain size has been sampled monthly since 2008. By using a combination of direct sampling, sediment cores and synoptic sampling via a digital camera, these data show (i) D50 consistently coarsens in the seaward direction across the intertidal zone, by up to 45%, (ii) grain size consistently increases with depth over the top metre, by up to 36% and (iii) significant seasonal variations were present, with summer grain sizes up to 40% finer than winter values. The results demonstrate that beach grain size is highly variable in time and space and therefore choosing a single representative grain size, as is often done for coastal modeling purposes, can be misleading. FiguresReferencesRelatedDetails Recommended Coastal Sediments 2015Metrics History PDF download