When collecting coastal monitoring data, it is common practice to survey down to spring low tide to capture the maximum extent of the exposed subaerial beach. However, collecting topographic beach data is possible for only a few days per month. By reducing the seaward extent of the survey, the incurred costs and risks to the survey schedule could be greatly reduced. However, this would result in information loss at the lowest extremes of the subaerial beach. This study assesses the feasibility of predicting this part of the beach using deep learning neural networks based on partial beach profile data. A range of network architectures were tested alongside linear extrapolation, which was used as a baseline model. Each model was tested on three beaches with varying morphology, ranging from steep (reflective) to mildly sloping (dissipative). The presence of morphological features was found to play a dominant role in the accuracy of the predicted profiles; profiles with more pronounced cross-shore morphological features, such as sandbars, produced the highest error. While local connectivity of each network architecture was found to be the key factor in producing realistic profiles, the 1D Convolutional Neural Network was found to be the most effective with an average RMSE of between 0.026-0.119 m. This RMSE is not substantially larger than the vertical accuracy of current survey techniques (0.03 m), and the study found that errors of this magnitude have negligible effects when the survey data is used to calculate beach volumes and conduct numerical wave runup analysis to assess coastal flood risk.

There has been limited exploration of the nearshore zone of mixed sediment beaches despite being widespread globally. Our work aims to build a more complete picture of coastal change by looking at seabed evolution from the very upper reaches of the swash zone, down to the edge of the nearshore zone, at a variety of timescales. Bathymetry surveys, completed using both traditional and automated surface vessels collected single and multibeam sonar data over a 19-year period, were complimented by a shorter period of weekly radar sea surface roughness images which are indicative of nearshore bed morphology. Additionally, grab samples were collected from across the nearshore to show the bed sediments composition variation over a year, providing valuable insight on bed response to varying hydrodynamic conditions. Process based analysis gave long and cross shore drift rates to help understand the observed changes. We found that the nearshore zone experiences significantly larger volumetric bed changes in comparison to the upper beach but were limited to approximately +/-0.3 m, which is equivalent to the upper error limits of the surveyed data. The depth of closure, a term used to mark the offshore point of no change over a defined time scale, varied across the mixed sediment bay at both seasonal (ranging between –4.7 and –8.4 metres Ordnance Datum(mOD)) and decadal (ranging between –7.3 and –8.2 mOD) timescales, yet was consistently shallower than all predictive equations of this depth. Moreover, our results indicate a loss of volume in the nearshore zone over time which is coupled with a simultaneous steepening of the upper beach for two thirds of the frontage. The observed steepening poses questions for the current ‘hold the line’ management strategy, which is achieved through active beach management works, and accommodation space. Overall, our observations highlight the substantial sediment transport occurring within the predominantly sandy nearshore zone and demonstrate evidence of impacts to the upper shingle beach. Consequently, to ensure the sustainability of management practices in the upper beach, a comprehensive understanding of the nearshore dynamics becomes imperative. The presented findings emphasize the necessity of integrating nearshore considerations into coastal management strategies, providing a more holistic and effective approach to making sustainable management decisions.

Transverse finger bars have largely been associated with sandy coasts. Here we show that these features persist within a wider mixed sediment environment, adjacent to a shingle cuspate foreland, which has not been previously reported. Details of the bars' characteristics were gleaned from analysis of bathymetry data, whilst weekly migration rates were inferred from remote sensing of the sea surface roughness as a proxy of undulating bedforms, using X-band radar reflectance data. The bars were on average 380 m long, had wavelengths of similar to 160 m, amplitudes of approximately 0.2 to 0.6 m and were orientated 30 degrees to shore normal. They were found in water depths between -3.3 and -5.8 m Ordnance Datum. The bars migrated by approximately 150 m over the first 'winter' observation period (15/11/2020-02/04/2021) and 70 m in the following winter period (Sept 2021-Feb 2022) but showed virtually no signs of movement during the intervening summer months. Analysis of hydrodynamic conditions suggested the bar mobility was related to the dominant longshore currents resulting from high angle, south westerly waves. Low amplitude rhythmic bedforms were also found in the upper beach, migrating at a similar rate to the nearshore bars, which are thought to be driven by high-angle wave instability.

Cross-front transport is a vital process in the offshore transport of terrestrial materials. The factors influencing cross-front transport are multifaceted and exhibit regional variability. As important factors regulating material transport patterns in the shelf seas of eastern China, the East Asian Winter Monsoon (EAWM) and Kuroshio current (including its branches) vary on multiple time scales, yet their role in controlling offshore transport is not fully understood. In this paper, cross-front offshore transport in the North Yellow Sea is chosen to investigate the aforementioned issue using numerical simulation. By excluding other potential processes for offshore transport, frontal instability is identified as the primary mechanism for offshore transport, which is triggered by winter storms (bursts of the EAWM); hence, the intensity of offshore transport is highly associated with the strength of winter storms on synoptic scales. However, on the inter-annual scale, the intensity of offshore transport is more likely regulated by the strength of the Kuroshio current, and a warming Kuroshio facilitates offshore transport. Although the role of each factor in controlling the intensity of offshore transport is delineated, the interactive effects of the EAWM and Kuroshio current on offshore transport are quite intricate, and how to quantitatively estimate their roles on multiple time scales remains a challenge using modelling. The results obtained from this study can be applied to analyse cross-front transport throughout the eastern China seas and bear significant implications for future studies on pollutant diffusion, nutrient distribution, and sediment transport in the coastal area.

Bottom current activity has been responsible for the formation of a multitude of erosional and depositional features recorded in chalk. Advanced knowledge on the mobility and transport of unlithified calcareous nannofossil ooze by bottom currents is increasingly important not only for understanding the deposition of ancient chalk, but also for modelling the behaviour of modern pelagic carbonate sediments. Whereas the erosional behaviour of very pure calcareous nannofossil ooze has recently been investigated, the effect of organic matter and clay minerals on the erosional behaviour of calcareous nannofossil ooze is as yet unquantified. The results of the present study are based on laboratory flume studies utilizing chalk ooze with varying concentrations of smectite clay (1 to 30 wt.%), two types of organic matter and bed porosity. Phytoplankton (Pavlova lutheri) was used as a proxy for particulate marine organic matter, and xanthan gum as a proxy for extracellular polymeric substances. The results show a significant decrease in nannofossil ooze mobility with increasing content of clay or marine organic matter. Organic matter is found to reduce erodibility at much lower concentrations than clay minerals at porosities equivalent to those of the seafloor. At lower porosities, corresponding to some depth below the seafloor, organic matter and clay minerals are less effective in bed stabilization. This suggests that clay minerals and especially organic matter will affect the likelihood of initiation of severe erosion on the seafloor, whereas their inhibiting effect will decrease as erosion scours progressively deeper into the sediment column. The effect of extracellular polymeric substances is more complex than marine organic matter, probably due to detachment of large aggregates from the bed and resulting increase in bed roughness. The choice of organic matter in sedimentological experiments may lead to significant differences in sediment behaviour and should therefore involve careful consideration.

Mixed sediment beaches are globally commonplace, yet little is understood of the extent and behaviour of their nearshore zones, potentially underestimating total cross-shore change. This paper is the first study to investigate the lateral and vertical extent of the active zone of the gravel-rich mixed beach in Pevensey Bay, a study site on the South East UK coastline. Morphodynamic change in the nearshore zone was studied at a range of timescales (days, months, years) suggesting that the width of the active nearshore zone correlated with the magnitude of the peak morphological change, whilst the depth of closure was influenced by bed slope, grain size and local variation in wave conditions. A conceptual model detailing the physical parameters responsible for local variations in the depth of closure was used to help understand differences between the observed and predicted depths of closure. Finally, ongoing chronic loss of sediment from below Mean Sea Level (MSL) was examined, which was shown to be independent of the depth of closure, but closely linked to the wider geomorphic setting of the bay.

Saltmarsh restoration such as managed realignment (MR) projects often include excavation of simplified tidal creek networks to improve drainage and marsh functioning, but their design is based on limited evidence. This paper compares the morphological evolution of creek networks in current MR projects in the UK with creek networks in natural saltmarshes, in order to provide improved guidance. The evolution of creek networks was monitored for 2-20 years post-breach at 10 MR sites across the UK by semi-automatically extracting 12 morphological creek parameters from lidar. The rates of creek evolution in MR sites are linked to the initial tidal, morphological and sedimentological conditions using principal component analysis, then compared with power law relationships of morphological equilibrium defined from 13 mature natural saltmarshes. MR creeks evolved into larger, more complex, better distributed systems, with a total creek length and volume statistically similar to their natural counterparts. However, the creek volume remains poorly distributed, with a mean distance between creeks ranging from 33 to 101 m versus 5-15 m for natural mature saltmarshes. MR creeks are also clustered around the breach area, leaving the marsh interior poorly drained. MR creek network morphologies remain strongly influenced by the initial creek template, as evidenced by unnaturally straight creeks inherited from former drainage ditches. A combination of external conditions (i.e., tidal range, sediment concentration in the wider estuary) and local conditions (i.e., site elevation, topographical heterogeneity, soil compaction) controls how easily creeks can form within MR sites. This in turn determines the amount of engineering effort required to help achieve reference site conditions. The end goal of creek design is to create MR sites that closely resemble reference site conditions, however the final design is also likely to be affected by a range of practical factors (e.g. engineering/cost) unique to each site and project.

There is an urgent need to address coastal dynamics as a fundamental interaction between physical and biological processes, particularly when trying to predict future biological-physical linkages under anticipated changes in environmental forcing. More integrated modelling, support for observational networks and the use of management interventions as controlled experimental exercises should now be vigorously pursued.

Energetic swell waves, particularly when they coincide with high water levels, can present significant coastal hazards. To better understand and predict these risks, analysis of the sea levels and waves that generate these events and the resulting coastal impacts is essential. Two energetic swell events, neither of which were predicted by modelled flood forecasts, occurred in quick succession in the English Channel. The first event, on 30 January 2021, produced moderate significant wave heights at or just below the 0.25 year return period along the southwest English coast, but combined with significant swell caused overtopping at East Beach in West Bay and at Chesil Beach. The second event, on 1 February 2021, generated the highest wave energy periods measured at many locations along the southern English coastline and, at high water, caused waves to run up over the promenades at Poole Bay and Christchurch Bay and caused overtopping at Hayling Island. Both events are described in detail, and their spatial footprints are mapped through a joint return period analysis using a copula function. It is found that typical joint return period analysis of water level and significant wave height underestimates potential impacts, while a joint consideration of water level and wave power ( P ) describes the 31 January event better and a joint consideration of water level and energy period ( T e ) best describes the 1 February event. Therefore, it is recommended that T e and P are adopted for coastal monitoring purposes, and that future studies further explore the use of both parameters for swell monitoring.

In the UK, coastal flooding and erosion are two of the primary climate-related hazards to communities, businesses, and infrastructure. To better address the ramifications of those hazards, now and into the future, the UK needs to transform its scattered, frag-mented coastal data resources into a systematic, integrated portal for quality-assured, pub-licly accessible open data. Such a portal would support analyses of coastal risk and resilience by hosting, in addition to data layers for coastal flooding and erosion, a diverse array of spatial datasets for building footprints, infrastructure networks, land use, popula-tion, and various socio-economic measures and indicators derived from survey and census data. The portal would facilitate novel combinations of spatial data layers to yield scientifi-cally, societally, and economically beneficial insights into UK coastal systems.

Few studies focus on the changing morphology of the nearshore zone of mixed sediment beaches, despite the fact that these beaches are found across the world. In the UK, these beaches make up ~25% of the coastline, and are often utilised as a first line of defence against coastal flooding. In Pevensey Bay, East Sussex, active beach management (sediment recycling and recharge) maintains the mixed gravel barrier beach to protect around 10,000 properties, culturally significant landmarks and internationally important wildlife sites. During the past 25 years, this management approach has successfully maintained the volume of the upper shingle part of the beach. However, the sandy foreshore area is experiencing a continuing loss of 8000 m3 of sediment per annum.This study seeks to understand the drivers behind the sustained loss of volume. Examination of multibeam bathymetry data revealed the presence of transverse finger bars with a wavelength of approximately 80 – 120 m, orientated at 45 degrees from the shoreline in the subtidal zone extending between the -3.0 to -6.0 mOD contours. Sediment grab samples taken perpendicular to the crests and troughs, revealed the surface sediments to be comprised of very well sorted fine sand, with D50 ranging between 150 – 169mm. Strong tidal currents flowing over these bed features modulate the sea surface roughness which can be detected in the X-band radar reflectance imagery. Using weekly averages of X-band radar reflectance imagery we show that the bars were a permanent feature over the 18-month period of observation and provide an indicative migration rate of approximately one wavelength a year to the east, which was validated against monthly bathymetric data. This novel approach of studying mobile sea bed features revealed a steady migration rate during the winter months, and virtually no movement during the summer period, suggests that the movement of the bars is driven by relatively higher energy south westerly waves. It is thought that the movement of these bars may be linked to erosive and accretive pulses which move easterly across the bay on the upper beach face. Understanding the process dynamics and broader role within the bay-wide sediment budget of these features is essential in comprehending the loss of sediment from the bay and will contribute to the future sustainable management of the site, where the management strategy for the next 100 years is currently under review.

In coastal areas, biofilms are often subject to disturbance by hydrodynamic forcing, bioturbation and human activities. These factors affect the influences biofilms have on the sediment. To reveal these effects, we studied laboratory-incubated and field-collected biotic sediments reworked by disturbances, and examined their stabilities and three-dimensional microstructures using laboratory annular flume tests and a wet-staining X-ray microcomputed tomography method. We find that, when subject to disturbance, biofilms do not always establish mat-like matrices that firmly armor the seabed and bio-stabilize sediments, but instead, have a range of effects on sediment stability, including both bio-stabilization and destabilization. Disturbance considerably alters microbial influences on sediment stability, but is not the only control. Given equal disturbance, whether or not sediments are bio-stabilized largely depends on the state of bio-sediment formation. At a relatively well-developed state, an organic-rich, adhesive polymer network tightly interconnects large amounts of sediment particles into aggregates, forms complex internal structures, and enhances sediment stability. By contrast, some bio-sediment formations only ever reach a less well-developed state, where scattered organic patches bind relatively few particles into aggregates and reduce sediment stability. Microbial growth likely has two opposing effects on sediment stability, by enhancing either weight/friction or lift/drag on aggregated particles. The former has the positive effect of enhancing sediment stability, whereas the latter can result in greater flow resistance and so have the opposite effect. A conceptual framework is put forward to characterize the different states of bio-sediment formation and their distinct effects on sediment stability.

Coastal defences have long provided protection from erosion and flooding to cities, towns and villages. In many parts of the world, continued defence is being questioned due to both environmental, sustainability and economic considerations. This is exemplified in England and Wales, where strategic Shoreline Management Plans envisage realignment of many protected coasts, often with low population densities, over the coming decades. The policy transition from protection to realignment is often resisted by affected communities and can have high political costs. Whilst some preparations for such transitions have been made, the communities affected are often not fully aware of the implications of policy change, and this brings the potential for blight. In this paper, we investigate the challenges of implementing transitions in coastal policy within England and Wales. The analysis is based on data obtained from three workshops held in 2019 that were attended by council members, engineers, planners, scientists and other relevant professionals. Five conditions are found to promote contention: (i) policy actors with competing priorities and different decision making time frames (immediate to decadal to a century); (ii) divergence between regulations and ad hoc political decisions (e.g. in relation to the demand for new housing); (iii) limited or non-existent funding to support policy transition; (iv) community expectation that protection is forever; and (v) a disconnection between people and ongoing coastal change. Our research indicates that transitions can be better supported through: (1) integrated multi-scalar preparedness for coastal change; (2) an accessible evidence base and future vision to nurture political confidence in adaptation; and (3) defined, time-bound and accessible diverse funding streams to achieve transitions. Critically, these generic actions need to be embedded within the local political and planning system to facilitate transition to more sustainable coasts and their communities.

Sea surface temperature (SST) trends along the south coast of England (northern English Channel) were examined based on data from systematic buoy measurements deployed by the National Network of Regional Coastal Monitoring Programmes of England (NNRCMP) since 2003. These data were supplemented with: (1) long-term, coastal SST measurements by the Centre for Environment, Fisheries and Aquaculture Science (CEFAS); (2) global data sets compiled by the Hadley Centre since 1900, and (3) satellite-derived observations from Moderate Resolution Imaging Spectroradiometer (MODIS) (Aqua) since 2002. These data sets were used to evaluate de-seasoned nearshore trends in SST along the south coast of England and examine links to regional ocean-atmosphere teleconnections. The analyses of long-term, CEFAS data support the proposal that prior to the mid-1980s there were no de-seasoned trends in SST and conditions from year to year were relatively stable. Subsequently, interannual fluctuations appear to have increased, associated with a period of warming between 1985 and 2003 (0.28 degrees C/decade). Post 2003, interannual fluctuations in SST monitored by the NNRCMP buoys continued, and the warming trend appears to be greater (0.42 degrees C/decade). This trend in SST is greatest in the nearshore and decreases with distance offshore. The warming in SST also varied greatly from month to month. The greatest warming took place from December to March, whilst the least heating (and sometimes cooling) occurred between September and November. Analysis of Hadley (HadSST1.1) and MODIS data sets substantiated these trends. The greatest warming (post 2003) was found west of Portland Bill (up to 0.76 degrees C/decade) and decreased towards the Strait of Dover. Despite this west-to-east trend, all 12 NNRCMP stations between Penzance and Folkestone showed remarkably similar results, suggesting regional and global sources of heat rather than local sources. This is corroborated through wavelet coherence analysis linking SST anomalies to regional/global ocean-atmosphere teleconnection indices at seasonal scales.

Coastal wetlands provide crucial ecosystem services including flood protection and carbon storage, but are being lost rapidly worldwide to the combined effects of sea-level rise, erosion and coastal urbanisation. Managed Realignment (MR) aims to mitigate for these losses by restoring reclaimed land to tidal influence. Data of creek evolution is critical to assess the performance of design strategies and improve design and implementation practices. This data descriptor provides a dataset of the horizontal morphological evolution of creek systems from various initial conditions in 10 MR schemes across the UK. Using a semi-automated workflow, morphological creek parameters were extracted from 52 lidar datasets at 1 m horizontal resolution spanning 2 to 20 years post-breach. This constitutes the most comprehensive systematic monitoring of MR creek morphology to date. The dataset will assist future MR design and provide baseline morphological information for ecological and biogeochemical surveying.

In marine environments, the exchange of particles and solutes between the seafloor and overlying water column, known as benthic-pelagic (B/P) coupling is an important component in many biological and biogeochemical cycles. Key processes and drivers involved in this exchange display strongly seasonal variability, especially in temperate coastal environments. The magnitude and timings of these seasonal patterns however are not identical year-on-year, and the influence of this inter-annual variability on the rate and direction of B/P exchange, as well as the influence of longer term, multi-year trends, are less well understood. In this current study, multi-year temporal patterns of benthic-pelagic solute and particle exchange were investigated on the examples of particulate organic carbon and dissolved inorganic nitrogen time series data, to assess connections between inter- and multi-annual processes and characterize their nature and what drives them. To this end, a decadal (2009–2018) time-series dataset that combines biological, physical, meteorological and chemical measurements from the Western Channel Observatory, Plymouth, UK was analysed in combination with supplementary data from several environmental monitoring agencies. Time-series decomposition using seasonal decomposition with locally estimated scatterplot smoothing revealed that the main causes of inter-annual variability were extreme outlier events, some of which were influential enough to cause multi-annual trends. Stochastic meteorological and biological extremes, such as exceptional storms and phytoplankton blooms explained a large proportion of outlier events in the time series. Global-scale climatic fluctuations, such as North Atlantic Oscillation (NAO) and Southern Oscillation Index were reflected in benthic-pelagic exchange trends when they co-occurred in an additive manner (e.g. positive NAO and El Niño). The importance of multi-parameter long-term observatories, such as the Western Channel Observatory, is highlighted, and the use of transdisciplinary time-series datasets to identify individual events which have large ecosystem-level impacts is demonstrated. In order to identify and monitor long-term effects, such as climate trends or decadal global ocean cycles, multi-decadal sustained observations are of vital importance.

Resilience is widely seen as an important attribute of coastal systems and, as a concept, is increasingly prominent in policy documents. However, there are conflicting ideas on what constitutes resilience and its operationalisation as an overarching principle of coastal management remains limited. In this paper, we show how resilience to coastal flood and erosion hazard could be measured and applied within policy processes, using England as a case study. We define resilience pragmatically, integrating what is presently a disparate set of policy objectives for coastal areas. Our definition uses the concepts of resistance, recovery and adaptation, to consider how the economic, social and environmental dimensions of coastal systems respond to change. We develop a set of composite indicators for each dimension, grounded empirically with reference to national geospatial datasets. A prototype Coastal Resilience Model (CRM) has been developed, which combines the dimensions and generates a quantitative resilience index. We apply it to England's coastal hazard zone, capturing a range of different stakeholder perspectives using relative indicator weightings. The illustrative results demonstrate the practicality of formalising and quantifying resilience. To re-focus national policy around the stated desire of enhancing resilience to coastal flooding and erosion would require firm commitment from government to monitor progress towards resilience, requiring extension of the present risk-based approach, and a consensus methodology in which multiple (and sometimes conflicting) stakeholder values are explicitly considered. Such a transition may also challenge existing governance arrangements at national and local levels, requiring incentives for coastal managers to engage with and apply this new approach, more departmental integration and inter-agency cooperation. The proposed Coastal Resilience Model, with the tools to support planning and measure progress, has the potential to help enable this transition.

In coastal temperate environments, many processes known to affect the exchange of particulate and dissolved matter between the seafloor and the water column follow cyclical patterns of intra-annual variation. This study assesses the extent to which these individual short term temporal variations affect specific direct drivers of seafloor-water exchanges, how they interact with one another throughout the year, and what the resulting seasonal variation in the direction and magnitude of benthic-pelagic exchange is. Existing data from a multidisciplinary long-term time-series from the Western Channel Observatory, United Kingdom, were combined with new experimental and in situ data collected throughout a full seasonal cycle. These data, in combination with and contextualized by time-series data, were used to define an average year, split into five 'periods' (winter, pre-bloom, bloom, post-bloom, and autumn) based around the known importance of pelagic primary production and hydrodynamically active phases of the year. Multivariate analyses were used to identify specific sub-sets of parameters that described the various direct drivers of seafloor-water exchanges. Both dissolved and particulate exchange showed three distinct periods of significant flux during the year, although the specific timings of these periods and the cause-effect relationships to the direct and indirect drivers differed between the two types of flux. Dissolved matter exchange was dominated by an upward flux in the pre-bloom period driven by diffusion, then a biologically induced upward flux during the bloom and an autumn downward flux. The latter was attributable to the interactions of hydrodynamic and biological activity on the seafloor. Particulate matter exchanges exhibited a strongly hydrologically influenced upward flux during the winter, followed by a biologically induced downward flux during the bloom and a second period of downward flux throughout post-bloom and autumn periods. This was driven primarily through interactions between biological activity, and physical and meteorological drivers. The integrated, holistic and quantitative data-based analysis of intra-annual variability in benthic/pelagic fluxes presented in this study in a representative temperate coastal environment, demonstrates not only the various process' inter-connectivity, but also their relative importance to each other. Future investigations or modeling efforts of similar systems will benefit greatly from the relationships and baseline rules established in this study.

Exchanges of solutes and solids between the sea floor and water column are a vital component of ecosystem functioning in marine habitats around the globe. This review explores particle and solute exchange processes, the different mechanisms through which they interact at the ecosystem level, as well as their interdependencies. Solute and particle exchange processes are highly dependent on the characteristics of the environment within which they takes place. Exchange is driven directly by a number of factors, such as currents, granulometry, nutrient, and matter inputs, as well as living organisms. In turn, the occurrence of exchanges can influence adjacent environments and organisms. Major gaps in the present knowledge include the temporal and spatial variation in many of the processes driving benthic/pelagic exchange processes and the variability in the relative importance of individual processes caused by this variation. Furthermore, the accurate assessment of some anthropogenic impacts is deemed questionable due to a lack of baseline data and long-term effects of anthropogenic actions are often unknown. It is suggested that future research should be transdisciplinary and at ecosystem level wherever possible and that baseline surveys should be implemented and long-term observatories established to fill the current knowledge gaps.