The interactive relationship between coastal erosion and flood risk

Coastal erosion and flooding are hazards that, when combined with facilitative pathways and vulnerable receptors, represent sources of coastal risk. Erosion and flooding risks are often analysed separately owing to complex relationships between driving processes, morphological response and risk receptors. We argue that these risks should be considered jointly and illustrate this through discussion of three ‘expressions’ of this interactive relationship: coastal morphology modifies flood hazard; future flood risk depends on changing shoreline position; and the simultaneous occurrence of erosion–flooding events. Some critical thoughts are offered on the general applicability of these expressions and the implications for coastal risk management policy. This research is funded by the NERC/ESRC Data, Risk and Environmental Analytical Methods (DREAM) Centre, Grant/Award Number: NE/M009009/

Reconstructing and understanding the impacts of storms and surges, southern North Sea

Coastal barriers are ubiquitous globally and provide a vital protective role to valuable landforms, habitats and communities located to landward. They are, however, vulnerable to extreme water levels and storm wave impacts. A detailed record of sub-annual to annual; decadal; and centennial rates of shoreline retreat in frontages characterized by both high (> 3 m) and low (< 1 m) dunes is established for a barrier island on the UK east coast. For four storms (2006–2013) we match still water levels and peak significant wave heights against shoreline change at high levels of spatial densification. The results suggest that, at least in the short-term, shoreline retreat, of typically 5–8 m, is primarily driven by individual events, separated by varying periods of barrier stasis. Over decadal timescales, significant inter-decadal changes can be seen in both barrier onshore retreat rates and in barrier extension rates alongshore. Whilst the alongshore variability in barrier migration seen in the short-term remains at the decadal scale, shoreline change at the centennial stage shows little alongshore variability between a region of barrier retreat (at 1.15 m a$^{−1}$) and one of barrier extension. A data-mining approach, synchronizing all the variables that drive shoreline change (still water level, timing of high spring tides and peak significant wave heights), is an essential requirement for validating models that predict future shoreline responses under changing sea level and storminess.This paper was completed while the first author (SB) was a recipient of a Leverhulme Research Fellowship (RF-2015-045) for a project entitled Development and Application of a shoreline response model. This paper is a contribution to NERC BESS Consortium grant A hierarchical approach to the examination of the relationship between biodiversity and ecosystem service flows across coastal margins (grant reference NE/J015423/1). Table 1 reports information gathered as part of an EU FP7 Collaborative Project (grant agreement no: 603458) Resilience-Increasing Strategies for Coasts – toolkit (http://www.risckit.eu).This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1002/esp.390

Southern North Sea storm surge event of 5 December 2013: Water levels, waves and coastal impacts

The storm surge event that affected the coastal margins of the southern North Sea on 5–6 December 2013 produced the highest still water levels on record at several tide gauges on the UK east coast. On east-facing coasts south of the Humber estuary and north-facing Norfolk, water levels were higher than in the twentieth century benchmark surge event of 31 January–1 February 1953. Maximum significant wave heights were highest off the North Norfolk coast (peak Hs = 3.8 m offshore, 2.9 m inshore) and lowest off the Suffolk coast (Hs = 1.5–1.8 m inshore); comparable offshore wave heights in 1953 were 7–8 m and ca. 3 m. The lower wave heights, and their short duration, in 2013 explain both localised breaching, overtopping, and back-barrier flooding associated with gravel ridges and relatively low earthen banks as well as the lack of failure in more highly-engineered coastal defences. On barrier coasts and within estuaries, the signal of maximum runup was highly variable, reflecting the modification of the tide–surge–wave signal by inshore bathymetry and the presence of a range of coastal ecosystems. The landscape impacts of the December 2013 surge included the notching of soft rock cliffs and cliffline retreat; erosion of coastal dunes; and the augmentation or re-activation of barrier island washover deposits. Whilst surge event-related cliff retreat on the rapidly eroding cliffs of the Suffolk coast lay within the natural variability in inter-annual rates of retreat, the impact of the surge on upper beach/sand dune margins produced a pulse of shoreline translation landwards equivalent to about 10 years of ‘normal’ shoreline retreat. The study of east coast surges over the last 60 years, and the identification of significant phases of landscape change — such as periods of rapid soft rock cliff retreat and the formation of new gravel washovers on barrier islands — points to the importance of high water levels being accompanied by high wave activity. Future developments in early warning systems and evacuation planning require information on the variable impacts of such extreme events.This paper is a contribution to NERC BESS Consortium grant A hierarchical approach to the examination of the relationship between biodiversity and ecosystem service flows across coastal margins (grant reference NE/J015423/1). Table 5 incorporates information gathered as part of an EU FP7 Collaborative Project Resilience-Increasing Strategies for Coasts — toolkit (RISC_KIT).This is the final published version. It first appeared at http://www.sciencedirect.com/science/article/pii/S0012825215000628#

Attainable standards of accuracy in the determination of Holocene sea levels in the Central Pacific: Introductory note

The research underpinning Stoddart and Murphy’s paper ‘Attainable standards of accuracy in the determination of Holocene sea-levels in the Central Pacific’ was undertaken in 1990–1993. This was a time when topographic survey was on the cusp of moving from traditional ground-based levelling surveys, from fixed, sea level-related benchmarks, to methods based on satellite altimetry. The former approach required surveys to be related to a well-defined tidal record (as detailed by Stoddart, 1978), while the latter effectively removed the need for a local datum by providing a common, global reference point, essentially the centre of the earth. As Stoddart and Murphy themselves perceptively noted ‘New mobile global positioning systems (GPS) and satellite altimetry surveys hold out the prospect of relatively high accuracy surveying even on remote islands’

Storm impacts and shoreline recovery: Mechanisms and controls in the southern North Sea

Storm impacts play a significant role in shoreline dynamics on barrier coastlines. Furthermore, inter-storm recovery is a key parameter determining long-term coastal resilience to climate change, storminess variability and sea level rise. Over the last decade, four extreme storms, with strong energetic waves and high still water levels resulting from high spring tides and large skew surge residuals, have impacted the shoreline of the southern North Sea. The 5th December 2013 storm, with the highest run-up levels recorded in the last 60 years, resulted in large sections of the frontline of the North Norfolk coast being translated inland by over 10 m. Storms in March and November 2007 also generated barrier scarping and shoreline retreat, although not on the scale of 2013. Between 2008 and 2013, a calm period, recovery dominated barrier position and elevation but was spatially differentiated alongshore. For one study area, Scolt Head Island, no recovery was seen; this section of the coast is being reset episodically landwards during storms. By contrast, the study area at Holkham Bay showed considerable recovery between 2008 and 2013, with barrier sections developing seaward through foredune recovery. The third study area, Brancaster Bay, showed partial recovery in barrier location and elevation. Results suggest that recovery is promoted by high sediment supply and onshore intertidal bar migration, at rates of 40 m a$^{−1}$. These processes bring sand to elevations where substrate drying enables aeolian processes to entrain and transport sand from upper foreshores to foredunes. We identify three potential sediment transport pathways that create a region of positive diffusivity at Holkham Bay. During calm periods, a general westward movement of sediment from the drift divide at Sheringham sources the intertidal bar and foredune development at Holkham Bay. However, during and following storms the drift switches to eastward, not only on the beach itself but also below the – 7 m isobath. Sediment from the eroding barrier at Brancaster Bay, and especially Scolt Head Island, also sources the sediment sink of Holkham Bay. Knowledge of foredune growth and barrier recovery in natural systems are vital aspects of future coastal management planning with accelerated sea-level rise and storminess variability.This research was undertaken while SMB held a Research Fellowship awarded by The Leverhulme Trust. Information on alongshore variations in water level was collected under EU FP7 Collaborative Project (grant agreement no: 603458) ‘Resilience-increasing Strategies for Coasts – toolkit’ (http://www.risckit.eu). The research is also a contribution to UK NERC BLUECoast Project (NE/N015924/1)

Impact of management regime and regime change on gravel barrier response to a major storm surge

Gravel barriers represent physiographic, hydrographic, sedimentary, and ecological boundaries between inshore and open marine offshore environments, where they provide numerous important functions. The morphosedimentary features of gravel barriers (e.g., steep, energy reflective form) have led to their characterization as effective coastal defense features during extreme hydrodynamic conditions. Consequently, gravel barriers have often been intensively managed to enhance coastal defense functions. The Blakeney Point Barrier System (BPBS), U.K., is one such example, which offers the opportunity to investigate the impact of alternative management regimes under extreme hydrodynamic conditions. The BPBS was actively re-profiled along its eastern section from the 1950s to the winter of 2005, whilst undergoing no active intervention along its western section. Combining an analysis of remotely sensed elevation datasets with numerical storm surge modeling, this paper finds that interventionist management introduces systemic differences in barrier morphological characteristics. Overly steepened barrier sections experience greater wave run-up extents during storm surge conditions, leading to more extreme morphological changes and landward barrier retreat. Furthermore, while high, steep barriers can be highly effective at preventing landward flooding, in cases where overwashing does occur, the resultant landward overtopping volume is typically higher than would be the case for a relatively lower crested barrier with a lower angled seaward slope. There is a growing preference within coastal risk management for less interventionist management regimes, incorporating natural processes. However, restoring natural processes does not immediately or inevitably result in a reduction in coastal risk. This paper contributes practical insights regarding the time taken for a previously managed barrier to relax to a more natural state, intermediary morphological states, and associated landward water flows during extreme events, all of which should be considered if gravel barriers are to be usefully integrated into broader risk management strategies.</jats:p

Consumption of cocoa flavanols results in acute improvements in mood and cognitive performance during sustained mental effort

Cocoa flavanols (CF) positively influence physiological processes in ways that suggest their consumption may improve aspects of cognitive function. This study investigated the acute cognitive and subjective effects of CF consumption during sustained mental demand. In this randomized, controlled, double-blinded, balanced, three period crossover trial 30 healthy adults consumed drinks containing 520 mg, 994 mg CF and a matched control, with a three-day washout between drinks. Assessments included the state anxiety inventory and repeated 10-min cycles of a Cognitive Demand Battery comprising of two serial subtraction tasks (Serial Threes and Serial Sevens), a Rapid Visual Information Processing (RVIP) task and a mental fatigue scale, over the course of 1 h. Consumption of both 520 mg and 994 mg CF significantly improved Serial Threes performance. The 994 mg CF beverage significantly speeded RVIP responses but also resulted in more errors during Serial Sevens. Increases in self-reported mental fatigue were significantly attenuated by the consumption of the 520 mg CF beverage only. This is the first report of acute cognitive improvements following CF consumption in healthy adults. While the mechanisms underlying the effects are unknown they may be related to known effects of CF on endothelial function and blood flow

Safety and efficacy of fluticasone propionate in the topical treatment of skin diseases

Fluticasone propionate - the first carbothioate corticosteroid - has been classified as a potent anti-inflammatory drug for dermatological use. It is available as 0.05% cream and 0.005% ointment formulations for the acute and maintenance treatment of patients with dermatological disorders such as atopic dermatitis, psoriasis and vitiligo. This glucocorticoid is characterized by high lipophilicity, high glucocorticoid receptor binding and activation, and a rapid metabolic turnover in skin. Although skin blanching following fluticasone propionate exceeds that of corticosteroids of medium strength, several clinical trials demonstrate a low potential for cutaneous and systemic side-effects, even in difficult-to-treat areas like the face, the eyelids and intertriginous areas. Even among paediatric patients with atopic dermatitis, fluticasone propionate proved to be safe and effective. These pharmacological and clinical properties are reflected by the high therapeutic index of this glucocorticoid

Understanding spatio-temporal barrier dynamics through the use of multiple shoreline proxies

At the coast, risk arises where, and when, static human developments are situated within dynamic surroundings. Barrier islands are often sites of heightened coastal risk since they frequently support substantial human populations and undergo extensive morphological change owing to their low-lying form and persistence in energetic hydrodynamic and meteorological conditions. Using the mixed sand-gravel barrier of Blakeney Point, this study argues that to avoid an only partial understanding of coastal zone processes, it is necessary to make use of multiple shoreline proxies, capturing processes operating both at different timescales and different cross-shore positions. Here, five shoreline proxies were extracted from three data sources. Shoreline error was quantified and compared to observed shoreline change rates to establish proxy-specific, appropriate timescales for shoreline change analysis. The map derived Mean High Water Line at Blakeney Point revealed landward retreat of −0.61 m a−1 over the past 130 years with a shift from drift- towards swash-alignment of the barrier since 1981. Over the past 24 years, the High Water Line, Ridge Line and Vegetation Line reveal proxy-specific response to management regime change. The termination of barrier reprofiling of the eastern section of the barrier has resulted in increased sediment release to the downdrift barrier terminus, buffering retreat there at the expense of the updrift section. The Vegetation Line represents an effective proxy for storm-driven overwash with maximum shoreline retreat during surge events of 172 m, illustrating a strong event-driven component to barrier morphodynamics. By comparison to the other proxies, the LiDAR (Light Detection and Ranging) derived Mean High Water Line offers relatively limited insights into barrier dynamics, emphasising the importance of multi-proxy approaches. In the face of technological advance, we demonstrate the continued importance of critical attention towards the dependencies that exist between shoreline proxy selection and the processes that can be observed as a result.This work was funded by the NERC/ESRC Data, Risk and Environmental Analytical Methods (DREAM) CDT, Grant/Award Number: NE/M009009/1. It is also a contribution to the NERC-funded project “Physical and Biological dynamic coastal processes and their role in coastal recovery” (BLUE-coast), Grant Award Number: NE/N015924/1

Assessment of sub-Nyquist deterministic and random data sampling techniques for operational modal analysis

This paper assesses numerically the potential of two different spectral estimation approaches supporting non-uniform in time data sampling at sub-Nyquist average rates (i.e., below the Nyquist frequency) to reduce data transmission payloads in wireless sensor networks (WSNs) for operational modal analysis (OMA) of civil engineering structures. This consideration relaxes transmission bandwidth constraints in WSNs and prolongs sensor battery life since wireless transmission is the most energy-hungry on-sensor operation. Both the approaches assume acquisition of sub-Nyquist structural response acceleration measurements and transmission to a base station without on-sensor processing. The response acceleration power spectral density matrix is estimated directly from the sub-Nyquist measurements and structural mode shapes are extracted using the frequency domain decomposition algorithm. The first approach relies on the compressive sensing (CS) theory to treat sub-Nyquist randomly sampled data assuming that the acceleration signals are sparse/compressible in the frequency domain (i.e., have a small number of Fourier coefficients with significant magnitude). The second approach is based on a power spectrum blind sampling (PSBS) technique considering periodic deterministic sub-Nyquist “multi-coset” sampling and treating the acceleration signals as wide-sense stationary stochastic processes without posing any sparsity conditions. The modal assurance criterion (MAC) is adopted to quantify the quality of mode shapes derived by the two approaches at different sub-Nyquist compression rates (CRs) using computer-generated signals of different sparsity and field-recorded stationary data pertaining to an overpass in Zurich, Switzerland. It is shown that for a given CR, the performance of the CS-based approach is detrimentally affected by signal sparsity, while the PSBS-based approach achieves MAC>0.96 independently of signal sparsity for CRs as low as 11% the Nyquist rate. It is concluded that the PSBS-based approach reduces effectively data transmission requirements in WSNs for OMA, without being limited by signal sparsity and without requiring a priori assumptions or knowledge of signal sparsity