Morphodynamic variability of high-energy macrotidal beaches, Cornwall, UK

The full text is under embargo until 01.04.16

Modelling storm response on gravel beaches using XBeach-G

EPRSC New Understanding and Prediction of Storm Impacts on Gravel beaches (NUPSIG; EP/H040056/1) and Adaptation and Resilience of Coastal Energy Supply (ARCEoS; EP/IO35390/1). The full text is under embargo until 01.12.15. Published by ICE Publishin

The extreme 2013/2014 winter storms: Beach recovery along the southwest coast of England

publisher: Elsevier articletitle: The extreme 2013/2014 winter storms: Beach recovery along the southwest coast of England journaltitle: Marine Geology articlelink: http://dx.doi.org/10.1016/j.margeo.2016.10.011 content_type: article copyright: © 2016 The Authors. Published by Elsevier B.V

Coastal dune dynamics in embayed settings with sea-level rise – Examples from the exposed and macrotidal north coast of SW England

Coastal dune systems are natural forms of coastal defence, but are expected to exhibit increased erosion rates due to climate change impacts, notably sea-level rise and, potentially, increased storminess. This is especially the case in embayed coastal settings, i.e., where there are no significant sediment inputs into the beach/dune system from longshore sources. Dune development is closely linked to that of beaches that lie seaward, but their temporal dynamics tend to be asynchronous. So, whereas beaches are generally highly variable over a short- to medium-term (event–decadal) time scales, potentially obscuring a longer-term (decadal–centennial) sea-level signal, dunes display a low-pass filtered response which may contain a sea-level signal. In this study, we investigate the decadal-scale, inter-annual dynamics of 25 embayed coastal dune systems along the exposed and macrotidal north coast of SW England. We then compare the observed behaviour with that hindcasted from simple parametric models and forecast future dune retreat rates due to sea-level rise. We show that practically all exposed dune systems show retreat with a regionally-averaged retreat rate of the dune foot of 0.5 m yr−1. The majority of retreat occurred over a small number of especially energetic winters and it was found that dune retreat is not automatically linked to dune volumetric change. Many of the retreating dune systems display so called ‘dune roll-over’, characterised by removal of sediment from the dune face and deposition at the dune top. Observed dune retreat rates were 2–3 times larger than predicted using simple parametric retreat models forced by sea-level rise. This suggests that the retreat models are inappropriate and/or that sea-level rise in itself may be insufficient to explain the observed retreat and that increased winter storminess may be implicated. A key factor in driving dune retreat is considered to be the number of hours that waves reach the dune foot or the excess runup energy present at the dune foot elevation. Both sea-level rise and enhanced storminess will increase exposure of the dune foot to energetic wave action and this is expected to accelerate dune retreat rates in these settings. Application of parametric shoreline retreat models that account for the acceleration in rate of sea-level rise predicts c. 40 m of dune retreat by 2100 with a considerable range in retreat (20–75 m), resulting from uncertainty in model choice and parameterisation. Simply extrapolating the current dune retreat rate also results in c. 40 m of dune retreat by 2100, but this approach ignores the potential acceleration in dune retreat rate due to an increase in the rate of sea-level rise. The combination of analysis of multi-annual coastal dune morphological change along with application of dune retreat models can provide useful insights into future dune evolution for coastal planners and managers

A 15-year partnership between UK coastal scientists and the international beach lifeguard community

Drowning is a leading cause of unintentional fatalities around the world, yet on beaches is often preventable through public education campaigns and intervention activities from lifeguards. In 2006, the UK beach lifeguarding community approached the Coastal Processes Research Group (CPRG) at University of Plymouth, UK, with a need to better understand the key hazards on UK beaches and how to foresee and manage the associated risks. In some cases there simply was not sufficient scientifically-robust understanding of certain hazards (for example rip currents) available for lifeguard managers to make objective, data-driven decisions on how to manage them. This paper documents the resulting 15-year body of work, and reflects upon the education, outreach, and other research impacts that have been created, and lessons learned along the way. By furthering fundamental coastal processes understanding of such things as beach classification and rip current dynamics, as well as applying science to challenges such as predicting beach life-risk and times of peak bathing hazard, the ongoing collaboration between lifeguards and academics continues to inform beach safety management in a number of countries around the world. Initiating research with clear aims and objectives that are driven by, and developed in conjunction with, the end-user, as opposed to starting with outcomes prescribed to the end-user by academics, has been an important factor in the success (or failure) of these scientific ventures. CPRG's research activities in the field of beach safety has been scientifically rewarding and have achieved significant impacts. We attribute this to: (1) sustained level of high-quality research; (2) continued effort spent on building long-term relationships with end-users; (3) co-creation of dissemination material and tools; (4) acceptance that it takes time and effort to achieve research impact; and (5) critically evaluating and reflecting on the research impacts. Ultimately, the ongoing collaboration has contributed to a ‘continuing trend of decline in accidental fatalities around our coastlines’, and such collaborations in other parts of the world continue to play a vital role in reducing coastal drowning globally

The role of antiphase boundaries during ion sputtering and solid phase epitaxy of Si(001)

The Si(001) surface morphology during ion sputtering at elevated temperatures and solid phase epitaxy following ion sputtering at room temperature has been investigated using scanning tunneling microscopy. Two types of antiphase boundaries form on Si(001) surfaces during ion sputtering and solid phase epitaxy. One type of antiphase boundary, the AP2 antiphase boundary, contributes to the surface roughening. AP2 antiphase boundaries are stable up to 973K, and ion sputtering and solid phase epitaxy performed at 973K result in atomically flat Si(001) surfaces.Comment: 16 pages, 4 figures, to be published in Surface Scienc

In-situ Observations of Infragravity Response during Extreme Storms on Sand and Gravel Beaches

Billson, O.J.; Russell, P.; Davidson, M.; Poate, T.; Amoudry, L.O., and Williams, M.E., 2020. In-situ observations of infragravity response during extreme storms on sand and gravel beaches. Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 382-386. Coconut Creek (Florida), ISSN 0749-0208. Infragravity waves (frequency = 0.005 - 0.05 Hz) play a key role in coastal storm impacts such as flooding and beach/dune erosion. They are known to dominate the inner surf zone on low-sloping sandy beaches during storms. However, in large wave conditions, their importance on different beach types, of variable swell and wind-waves dominance, is largely unknown. Here, a new dataset is presented comprising in-situ observations during storm wave conditions (significant wave height of 3.3 m, peak periods of 18 s and return periods up to 1 in 60 years) from two contrasting sites: a low-sloping sandy beach and a steep gravel beach. Wave measurements were collected seaward of the breakpoint by wave buoys and bed-mounted acoustic Doppler current profilers, and through the surf zone using arrays of pressure transducers. Wave spectra showed contrasting evolution from the shoaling zone to the inner surf zone at the two sites. At the sandy beach, gravity band energy dissipated gradually as depth reduced, while infragravity band energy simultaneously increased, resulting in strongly infragravity-dominated wave spectra in the inner surf zone. At the steep gravel site, a rapid drop in short wave energy was observed, with limited growth of infragravity energy so that inner surf zone spectra showed a low energy peak in the infragravity band. The normalized bed slope parameter indicated whether infragravity waves were generated by bound long wave release or breakpoint forcing, showing that the former (latter) was dominant on the sandy (gravel) beach. In spite of these differences, the shoreline wave spectra under storm wave conditions were infragravity-dominated on both the sandy and gravel beaches