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The development of the marine renewable energy and offshore aquaculture sectors is susceptible to being affected by climate change. Consequently, for the long-term planning of these activities, a holistic view on the effects of climate change on energy resources and environmental conditions is required. Based on present climate and future climate scenario, favourable conditions for wind and wave energy exploitation and for farming six marine fish species are assessed using a suitability index over all European regional seas. Regarding available energy potential, the estimated changes in climate do not have direct impacts on the geographic distribution of potential regions for the energy industry (both wind and wave based), that is they pose no threat to this industry. Long-term changes in environmental conditions could however require adaptation of the aquaculture sector and especially of its exploitation areas. Opportunities for aquaculture expansion of the assessed species are identified. Possibilities for co-location of these activities are observed in the different climate scenarios. The evaluation of potential zones for the exploitation of marine renewable energy resources and offshore aquaculture represents a stepping-stone, useful for improving decision-making and assisting in the management of marine economies both in the short-term and in the long-term development of these sectors.

The ports sector is critical to global transport and trade. Climate change may compromise port operations, resulting in an increase in operational shutdowns and subsequent economic losses. Here, we present an analysis of historical global risk across the operations of 2,013 ports worldwide and the impacts under a high-end warming scenario, considering atmospheric and marine hazards, industry established operational thresholds, exposure and vulnerability. Increased coastal flooding and overtopping due to sea level rise, as well as the heat stress impacts of higher temperatures, are the main contributors to amplified risk. Ports located in the Pacific Islands, Caribbean Sea and Indian Ocean appear to be at extremely high risk by 2100, whereas those in the African Mediterranean and the Arabian Peninsula (Persian Gulf and Red Sea) are expected to experience very high risk. Estimating risks at the global scale cannot capture site-level details, but these results provide a benchmark for further research and decision-making. Global trade and transport depend on the resilience of the ports sector. Multi-hazard operational risks are estimated for 2,013 ports under historical climate and future warming; of the marine and atmospheric hazards considered, coastal flooding, wave overtopping and heat stress increase risk most.

The implementation of a quantum computer requires both to protect information from environmental noise and to implement quantum operations efficiently. Achieving this by a fully fault-tolerant platform, in which quantum gates are implemented within quantum-error corrected units, poses stringent requirements on the coherence and control of such hardware. A more feasible architecture could consist of connected memories, that support error-correction by enhancing coherence, and processing units, that ensure fast manipulations. We present here a supramolecular {Cr7Ni}–Cu system which could form the elementary unit of this platform, where the electronic spin 1/2 of {Cr7Ni} provides the processor and the naturally isolated nuclear spin 3/2 of the Cu ion is used to encode a logical unit with embedded quantum error-correction. We demonstrate by realistic simulations that microwave pulses allow us to rapidly implement gates on the processor and to swap information between the processor and the quantum memory. By combining the storage into the Cu nuclear spin with quantum error correction, information can be protected for times much longer than the processor coherence., The implementation of a quantum computer requires protecting of information from noise and the ability to perform quantum gates. We present a molecular architecture providing both these ingredients, via an electronic spin 1/2 processor and a nuclear spin 3/2 memory.

Future projections of coastal erosion, which are one of the most demanded climate services in coastal areas, are mainly developed using top-down approaches. These approaches consist of undertaking a sequence of steps that include selecting emission or concentration scenarios and climate models, correcting models bias, applying downscaling methods, and implementing coastal erosion models. The information involved in this modelling chain cascades across steps, and so does related uncertainty, which accumulates in the results. Here, we develop long-term multi-ensemble probabilistic coastal erosion projections following the steps of the top-down approach, factorise, decompose and visualise the uncertainty cascade using real data and analyse the contribution of the uncertainty sources (knowledge-based and intrinsic) to the total uncertainty. We find a multi-modal response in long-term erosion estimates and demonstrate that not sampling internal climate variability?s uncertainty sufficiently could lead to a truncated outcomes range, affecting decision-making. Additionally, the noise arising from internal variability (rare outcomes) appears to be an important part of the full range of results, as it turns out that the most extreme shoreline retreat events occur for the simulated chronologies of climate forcing conditions. We conclude that, to capture the full uncertainty, all sources need to be properly sampled considering the climate-related forcing variables involved, the degree of anthropogenic impact and time horizon targeted. AT acknowledges the financial support from the FENIX Project by the Government of Cantabria. This research was also funded by the Spanish Government via the grant RISKCOADAPT (BIA2017-89401-R).

This material is based upon work supported by the National Fish and Wildlife Foundation and the U.S. Department of the Interior under grant 43932.This material is also based upon work supported by the National Science Foundation under grant SES‐1331399.This research was also supported in part by the Thomas F. and Kate Miller Jeffress Memorial Trust, Bank of America, Trustee. M. Maza, J.L. Lara, and I.J. Losada are indebted to the Spanish Ministry of Economy and Competitiveness for the funding provided in the RETOS INVESTIGACION 2014 (grant BIA2014‐59718‐R) grant program.

This paper presents the stability analysis of a non-conventional breakwater cross-section integrating an overtopping wave energy converter, named OBREC. The device consists of a traditional rubble-mound breakwater in which the upper part of the armour layer is replaced by a smooth ramp and a reservoir. The analysis of the structure is carried out by combining model scale experiments and numerical simulations based on the Volume-Averaged Reynolds Averaged Navier-Stokes (VARANS) equations. The numerical analysis is used to complete and extend the results of the physical model test campaign, providing a deeper understanding of the pressure distribution and resultant force behaviour in locations where laboratory measurements were difficult to obtain or not available. Results show that the maximum vertical and horizontal total forces on the device are not simultaneous. At the time instant of the maximum total horizontal force, the vertical force is zero or directed downward, due to the significant positive contribution of the force acting on the sloping ramp. Additional numerical simulations show the influence of the submerged ramp length on the forces acting on the structure using the global and local stability analysis. The presence of the shaft contributes positively to the global stability against the sliding failure mode by reducing the uplift force exerted on the horizontal base. Moreover, the stability analysis shows that the critical conditions for the global failure modes occur at different time instants.

Understanding the hydrodynamic performance of floating energy converters is a complex challenge. Hence, physical modelling is necessary to evaluate the performance of innovative designs and validate them. The present paper shows the experimental work performed to validate a new floating semisubmersible structure which combines wave energy converters (3 Oscillating Water Columns, OWC) and wind harvesting (5 MW wind turbine). To characterize the global response of the platform, as well as the OWCs’ performance, an innovative wave tank testing campaign was carried out at the Cantabria Coastal and Ocean Basin (CCOB). The multi-use platform was characterized under the incidence of regular wave tests (with and without wind), operational sea states and survival sea states (combining waves, currents and wind). During the tests wind was reproduced with a portable wind generator and the wind turbine was simulated as a drag disk. The OWC air turbines were experimentally conceptualized by different diameter openings on the upper part of each OWC. This paper describes the experimental testing campaign carried out at the CCOB and presents the most significant experimental results obtained, such as natural periods, movements, loads on the mooring system or accelerations, which are representative of the performance of the multi-use platform presented.

In this work we pilot a methodology to value the annual coastal protection benefits provided by mangroves in the Philippines and identify where these natural coastal defenses deliver the greatest protection. This is the first rigorous, engineering-based, nationwide evaluation of the effectiveness of mangrove habitats as natural defenses. By comparing flood damages for scenarios with and without mangroves, the study estimates the socioeconomic benefits for protecting people and property, to inform conservation and disaster risk reduction policies. Without mangroves, flooding and damages to people, property and infrastructure in the Philippines would increase annually around 25%. These habitats reduce flooding to 613,500 people/year, 23% of whom live below the poverty line. They also avert damages to 1 billion US$/year in residential and industrial property. If mangroves were restored to their 1950 distribution, there would be additional benefits to 267,000 people annually, including 61,500 people below poverty and an additional 453 mill. US$ in avoided damages. Currently, mangroves prevent more than 1.7 billion US$ in damages for extreme events (1-in-50-year). Ultimately, rigorous economic estimates of critical ecosystem services like this will help the national government to integrate the value of mangroves to people, into their national accounting systems.

Based on a novel approach, present-day and future spectral wind-wave conditions in a high-emission scenario from a seven-member wave climate projection ensemble are compared. The spectral analysis at the selected locations aids in understanding the propagation of swell projected changes from the generation areas across the ocean basins. For example, a projected increase in the energy from Southern Ocean swells can be observed in all ocean basins and both hemispheres, which is especially relevant in the west coast of North America due to the penetration of these swells beyond 30°N. Similarly, a consistent decrease in the energy of large northern Atlantic swells is noted close to the equator. This work provides evidence that assessments based on only integrated wave parameters (e.g., significant wave height and mean wave period) can mask information about the sign, magnitude, and robustness of the actual wave climate changes due to the offset of positive and negative variations within the spectrum, leading to a significant underestimation of the change associated with certain wave systems. HL and MM acknowledge the support by the Spanish Ministry of Science and Innovation (MICINN, grants FPU17/06203 and RYC-2014-16469, respectively). This work is funded by EXCEED (grant RTI2018-096449-B-I00) from the Spanish State Research Agency.

Extreme waves will undergo changes in the future when exposed to different climate change scenarios. These changes are evaluated through the analysis of significant wave height (Hs) return values and are also compared with annual mean Hs projections. Hourly time series are analyzed through a seven-member ensemble of wave climate simulations and changes are estimated in Hs for return periods from 5 to 100 years by the end of the century under RCP4.5 and RCP8.5 scenarios. Despite the underlying uncertainty that characterizes extremes, we obtain robust changes in extreme Hs over more than approximately 25% of the ocean surface. The results obtained conclude that increases cover wider areas and are larger in magnitude than decreases for higher return periods. The Southern Ocean is the region where the most robust increase in extreme Hs is projected, showing local increases of over 2 m regardless the analyzed return period under RCP8.5 scenario. On the contrary, the tropical north Pacific shows the most robust decrease in extreme Hs, with local decreases of over 1.5 m. Relevant divergences are found in several ocean regions between the projected behavior of mean and extreme wave conditions. For example, an increase in Hs return values and a decrease in annual mean Hs is found in the SE Indian, NW Atlantic and NE Pacific. Therefore, an extrapolation of the expected change in mean wave conditions to extremes in regions presenting such divergences should be adopted with caution, since it may lead to misinterpretation when used for the design of marine structures or in the evaluation of coastal flooding and erosion.

This paper and its companion (Di Paolo et al., 2020b) present near-far field coupling schemes of Navier-Stokes (NS) equations for high-fidelity numerical modelling of wave generation, transformation and interaction with structures. The computational domain is subdivided into near and far field zones (2D and 3D subdomains, respectively) in which the NS equations are solved adopting the Finite Volume Method. The couplings can be made through the one-way or two-way exchange of flow information, thus providing a complete tool for studying one or bi-directional processes in which the three-dimensional flow is expected to be confined in the near field. The global coupled system, which is built on the OpenFOAM® platform, is based on a multi-domain approach in which the sub-domains (i.e., 2D and 3D meshes) are built independently. In Part I, the coupling methodologies have been validated against full 3D models taking into account wave propagation under different conditions with excellent results and high efficiency. Part 2 (Di Paolo et al., 2020b) involves the validation and application of the proposed methodologies to complex wave-structure interaction studies.

Global mean sea level rise and its acceleration are projected to aggravate coastal erosion over the 21st century, which constitutes a major challenge for coastal adaptation. Projections of shoreline retreat are highly uncertain, however, namely due to deeply uncertain mean sea level projections and the absence of consensus on a coastal impact model. An improved understanding and a better quantification of these sources of deep uncertainty are hence required to improve coastal risk management and inform adaptation decisions. In this work we present and apply a new extraprobabilistic framework to develop shoreline change projections of sandy coasts that allows consideration of intrinsic (or aleatory) and knowledge-based (or epistemic) uncertainties exhaustively and transparently. This framework builds upon an empirical shoreline change model to which we ascribe possibility functions to represent deeply uncertain variables. The model is applied to two local sites in Aquitaine (France) and Castellón (Spain). First, we validate the framework against historical shoreline observations and then develop shoreline change projections that account for possible (although unlikely) low-end and high-end mean sea level scenarios. Our high-end projections show for instance that shoreline retreats of up to 200m in Aquitaine and 130m in Castellón are plausible by 2100, while low-end projections revealed that 58 and 37m modest shoreline retreats, respectively, are also plausible. Such extended intervals of possible future shoreline changes reflect an ambiguity in the probabilistic description of shoreline change projections, which could be substantially reduced by better constraining sea level rise (SLR) projections and improving coastal impact models. We found for instance that if mean sea level by 2100 does not exceed 1m, the ambiguity can be reduced by more than 50%. This could be achieved through an ambitious climate mitigation policy and improved knowledge on ice sheets. This research has been supported by the BRGM, IHCantabria and the ERA4CS-ECLISEA project (grant no. 690462).

Sea-level rise (SLR) is a major concern for coastal hazards such as flooding and erosion in the decades to come. Lately, the value of high-end sea-level scenarios (HESs) to inform stakeholders with low-uncertainty tolerance has been increasingly recognized. Here, we provide high-end projections of SLR-induced sandy shoreline retreats for Europe by the end of the 21st century based on the conservative Bruun rule. Our HESs rely on the upper bound of the RCP8.5 scenario &ldquo, likely-range&rdquo, and on high-end estimates of the different components of sea-level projections provided in recent literature. For both HESs, SLR is projected to be higher than 1 m by 2100 for most European coasts. For the strongest HES, the maximum coastal sea-level change of 1.9 m is projected in the North Sea and Mediterranean areas. This translates into a median pan-European coastline retreat of 140 m for the moderate HES and into more than 200 m for the strongest HES. The magnitude and regional distribution of SLR-induced shoreline change projections, however, utterly depend on the local nearshore slope characteristics and the regional distribution of sea-level changes. For some countries, especially in Northern Europe, the impacts of high-end sea-level scenarios are disproportionally high compared to those of likely scenarios.

In this paper, an extended numerical analysis of the “confined-crest impact” (hereinafter referred as “C–CI”), induced by non-breaking waves on recurved parapet walls, is presented to better understand the physics and characteristics of this impulsive wave phenomenon, which significantly depends on the geometry of the parapet (here made by a sector of circumference) as well as on non-breaking wave steepness. A dimensional analysis of the forces has been carried out and used to analyse the results obtained by numerical CFD computations. The numerical simulations, performed for different radii of curvature, opening angles and incoming wave characteristics (changing both the wave height H and wave period T), have shown that the maximum impulsive pressure: (i) takes place on the top of the recurved parapet and decreases moving towards the S W L , where it tends to vanish; (ii) tends to decrease as the radii of curvature and the incoming wave characteristics (wave height H and period T) increase. However, this reduction in the maximum pressure, is always accompanied by an increase of the forces acting on the recurved parapet and a decrease of the wave overtopping volumes. Moreover, the maximum wave induced pressures have been examined by means of regular and irregular wave conditions in order to analyse the possibility of schematising the effects (i.e. forces) of an irregular sea state with those of a regular one, providing an equivalent force and therefore saving computational time. Based on the new results, a schematization of the pressure diagram induced by the C–CI impact has been proposed, used to extend the Goda-Takahashi pressure diagrams, valid for vertical walls in non-breaking wave conditions, including recurved walls.

Coastal flood risks are rising rapidly. We provide high resolution estimates of the economic value of mangroves forests for flood risk reduction every 20 km worldwide. We develop a probabilistic, process-based valuation of the effects of mangroves on averting damages to people and property. We couple spatially-explicit 2-D hydrodynamic analyses with economic models, and find that mangroves provide flood protection benefits exceeding $US 65 billion per year. If mangroves were lost, 15 million more people would be flooded annually across the world. Some of the nations that receive the greatest economic benefits include the USA, China, India and Mexico. Vietnam, India and Bangladesh receive the greatest benefits in terms of people protected. Many (>45) 20-km coastal stretches particularly those near cities receive more than $US 250 million annually in flood protection benefits from mangroves. These results demonstrate the value of mangroves as natural coastal defenses at global, national and local scales, which can inform incentives for mangrove conservation and restoration in development, climate adaptation, disaster risk reduction and insurance We thank the supporting provided by the World Bank and the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) on the basis of a decision adopted by the German Bundestag. We also acknowledge financial support from the Spanish Ministry of Economy and Innovation (BIA2014-59718-R). Authors are grateful to the useful contributions provided by Borja González Reguero (University of Santa Cruz California), Antonio Espejo, Sheila Abad and Pedro Díaz Simal (IH Cantabria). Pelayo Menéndez acknowledge to the FPI grant from the Spanish Ministry of Economy and Innovation (BES-2015-074343). The authors acknowledge to the National Plan “RISKOADAPT” from the Spanish Ministry of Sciences, Innovation and Universities (BIA2017-89401-R).

Shoreline recession due to the combined effect of waves, tides and sea level rise is increasingly becoming a major threat to beaches, one of the main assets of seaside tourist destinations. Given such an uncertain future climate and the climate-sensitive nature of many decisions that affect the long term, there is a growing need to shift current approaches towards probabilistic frameworks able to take uncertainty into account. This study contributes to climate change research by exploring the effects of erosion on the recreation value of beaches as a key indicator in the tourism sector. The new paradigm relates eroded sand to geographic and socioeconomic aspects and other physical settings, including beach type, quality and accesses, yielding monetary estimates of risk in probabilistic terms. Additionally, we look into policy implications regarding tourism management, adaptation and risk reduction. The methodology was implemented in 57 beaches in Asturias (north of Spain).

One approach to identifying and mapping the state of marine biophysical conditions is the identification of large-scale ecological units for which conditions are similar and the strategies of management may also be similar. Because biological processes are difficult to directly record over large areas, abiotic characteristics are used as surrogate parameters. In this work, the Mediterranean Sea was classified into homogeneous spatial areas based on abiotic variables. Eight parameters were selected based on salinity, sea surface temperature, photosynthetically active radiation, sea-wave heights and depth variables. The parameters were gathered in grid points of 0.5° spatial resolution in the open sea and 0.125° in coastal areas. The typologies were obtained by data mining the eight parameters throughout the Mediterranean and combining two clustering techniques: self-organizing maps and the k-means algorithm. The result is a division of the Mediterranean Sea into seven typologies. For these typologies, the classification recognizes differences in temperature, salinity and radiation. In addition, it separates coastal from deep areas. The influence of river discharges and the entrance of water from other seas are also reflected. These results are consistent with the ecological requirements of the five studied seagrasses ( Posidonia oceanica , Zostera marina , Zostera noltei , Cymodocea nodosa , Halophila stipulacea ), supporting the suitability of the resulting classification and the proposed methodology. The approach thus provides a tool for the sustainable management of large marine areas and the ability to address not only present threats but also future conditions, such as climate change.

Although mangroves reduce the daily risk of flood for millions of people, it is still difficult to estimate the protection they provide for variable wave conditions and forest characteristics. This aspect is crucial for the promotion of conservation and restoration of mangrove forests and for the estimation of how the coastal protection service they provide will evolve over time. This paper presents evidence and a new method for the estimation of the relationship between mangrove forest age and wave attenuation. The forest under analysis is characterised by the age of the Rhizophora mangrove trees, where consideration is given to the differences in the maturity of its individual trees and the density of the forest. Environmental conditions are defined by water levels and incoming wave height and period. A set of empirical and analytical relations expressing wave attenuation as a function of the submerged solid volume fraction (SVF) are presented. Changes is tree morphology and forest characteristics with forest age, as well as the contribution of the tree canopy, are taken into account. Results indicate that, after restoration, it may take only 5 years to obtain a forest's maximum coastal protection capacity. Additionally, such capacity appears to be maintained throughout the forest's lifetime with minor variations, provided the forest is not affected by any conditions altering its health, such as extreme wave events or anthropogenic action that may modify its habitat. Our findings present a new approach to quantifying the protection provided by mangroves without requiring any calibration. These findings can also assist in planning mangrove restoration and assessing associated benefits by providing the incorporation of nature-based solutions or ecosystem-based adaptation into coastal management.

In the context of growing concern about the threat of flooding posed by climate change in coastal areas, the Spanish plan for coastal adaptation to climate change gave rise to stringent requirements on risk consequence estimates at the regional scale O (100 km). Within this framework, we propose a methodology that combines high space-time resolution climate information (reanalysis databases and projections), local data on exposure that accounts for the most relevant sectors, site-specific vulnerability functions, and flood risk consequence valuation, gridded at 5 m. This approach involves efficient multiple-forcing flood modeling, in which the connection between climate change and potential inundation is primarily established through the definition of a total water level index. This research tackles challenging issues, including the importance of incorporating the effects of existing coastal defenses and local wave effects in port areas, dealing with data at different spatial scales and sectors in an integrated way, and the impact of discounting. The results provide insights into the possible consequences of inaction for a range of future scenarios based on changes in climate and socio-economics over the most relevant sectors. With the goal of prioritizing adaptive action and the efficient assignment of funds, we propose a weight-based integration of the sectoral value-at-risk through the application of Bayesian techniques and expert judgment. The methodology described here was applied to a pilot case study on the coast of Asturias in northern Spain.

A family of heterometallic [Cat][TixMO(x+1)(O2CtBu)2x+2] rings is reported where Cat=a secondary or tertiary alkyl ammonium ion, x=7, 8 or 9, and M=FeIII, GaIII, CrIII, InIII and AlIII. The structures are regular polygons with eight, nine or ten vertices with each edge bridged by an oxide and two pivalates. The size of the ring formed is controlled by the alkylammonium cation present. In each case a homometallic by-product is found [Cat][TixO(x+1)(O2CtBu)2x−1].

This study presents the design, development, scheme and field validation of an early-alert ocean wave system. It is designed to automate, improve, analyse, design and manage the daily construction activities of any harbour at construction stage. The objective is threefold: a) maximise construction safety, with regards to well-known hazards which occur during construction, especially breakwaters that interact with high-energy sea states, b) optimise the transport, by means of specialised vessels, of the refill material, and c) to minimise the construction delay and disruption on a daily basis, thanks to short-term construction forecasting (96 h). The system, known as PATO, offers short-term sea states characteristics, at any point near harbour structures, and relevant wave-structure interaction parameters at any harbour construction stage. The system is able to assist harbour project managers by providing accurate ocean wave data through a user-friendly interface.

Global wave hindcasts provide wave climate information for long time periods which helps to improve our understanding of climate variability, long term trends and extremes. This information is extremely useful for coastal studies and can be used both directly or as boundary conditions for regional and local downscalings. This work presents the GOW2 database, a long-term wave hindcast covering the world coastline with improved resolution in coastal areas and along ocean islands. For developing the GOW2 hindcast, WAVEWATCH III wave model is used in a multigrid two-way nesting configuration from 1979 onwards. The multigrid includes a global grid of half degree spatial resolution, specific grids configured for the Arctic and the Antarctic polar areas, and a grid of higher resolution (about 25 km) for all the coastal locations at a depth shallower than 200 m. Available outputs include hourly sea state parameters (e.g. significant wave height, peak period, mean wave direction) and series of 3-h spectra at more than 40000 locations in coastal areas. Comparisons with instrumental data show a clear improvement with respect to existing global hindcasts, especially in semi-enclosed basins and areas with a complex bathymetry. The effect of tropical cyclones is also well-captured thanks to the high resolution of the forcings and the wave model setup. The new database shows a high potential for a variety of applications in coastal engineering.

The effect of vegetation patchiness on solitary wave propagation, attenuation and wave-induced forces is studied both experimentally and numerically. Vegetation patchiness is simulated with rigid cylinder configurations built by one, eight and four patches tested under emergent, near emergent and submerged conditions. These configurations are parameterized by means of a new parameter (equivalent length, Le), which is used to relate cylinders distribution with wave attenuation capacity. This new parameter allows comparing results for the three patches configurations. Larger attenuation rates are found for higher wave heights and shorter wave periods. The influence of water depth is also considered by means of the submergence ratio (SR) in order to account for the percentage of water column affected by vegetation. Higher attenuation rates are obtained for emergent conditions. High correlations are found between wave attenuation and a new set of parameters, the depth wave number (kLe × SR), that accounts for submergence conditions and field characteristics and a new Reynolds number ( R e s L e ), that is calculated considering the field vegetation dimensions affecting the flow. Experimental results are extended using IHFOAM, a three dimensional Navier-Stokes equations solver, to analyze wave forces on individual cylinders and wave propagation patterns showing the variability of forces magnitude and direction associated to vegetation patchiness.

We use a numerical model, already validated for this purpose, to simulate the effect of wave frequency spread on wave transformation and swash amplitudes. Simulations are performed for planar beach slope cases and for offshore wave spectra whose frequency spread changes over realistic values. Results indicate that frequency spread, under normally approaching waves, affects swash amplitudes. For moderately dissipative conditions, the significant infragravity swash increases for increasing values of the offshore frequency spread. The opposite occurs under extremely dissipative conditions. The numerical analysis suggests that this inverted pattern is driven by the effect that different distributions of incoming long?wave energy have on low?frequency wave propagation and dissipation. In fact, with large frequency spreads, wave groups force relatively short subharmonic waves that are strongly enhanced in the shoaling zone. This process leads to an infragravity swash increase for increasing frequency spread under moderately dissipative conditions in which low?frequency energy dissipation in shallow water is negligible or small. However, under extremely dissipative conditions, the significant low?frequency energy dissipation associated with large frequency spreads overturns the strong energy growth in the shoaling zone eventually yielding an infragravity swash decrease for increasing frequency spread. This work has been funded under (1) the RETOS INVESTIGACION 2014 (Grant BIA2014-59718-R) program of the Spanish Ministry of Economy and Competitiveness and (2) the NEPTUNE 2 project, L. R. 7/2007 by Regione Autonoma della Sardegna.

Historic coastal structures have played a key role in small- to medium-size ports, being the driving force for the local development of coastal communities. Because coastal managers require reliable risk-based analysis of the whole life cycle of these coastal structures, previous lifetimes should be studied. This is a differentiating factor with respect to the newly built breakwaters. For this reason, in this work, a methodology for assessing how the hydraulic performance of an expired lifetime has evolved over the years is presented. It is performed following a probabilistic approach due to the uncertainty related to both the involved variables (wave climate, geometrical and structural breakwater variables) and the hydraulic response of the structure. The first ones are characterized by reliable probability distribution functions. The second ones are characterized by reliable formulae for the analysis of the hydraulic response. However, their non-conventional designs located in shallow-water locations require site-dependent formulae. To overcome this problem, a novel methodology to apply CFD numerical models is presented. Finally, it is integrated in a high-resolution time-dependent probabilistic methodology which takes into account the stochastic behaviour of all the involved variables, coastal and structural processes with a good uncertainty level. This article is part of the theme issue ‘Environmental loading of heritage structures’.

Coastal development and climate change are dramatically increasing the risks of flooding, erosion, and extreme weather events. Coral reefs and other coastal ecosystems act as natural defenses against coastal hazards, but their degradation increases risk to people and property. Environmental degradation, however, has rarely been quantified as a driver of coastal risk. In Quintana Roo, Mexico, a region on the Mexican Caribbean coast with an annual tourism economy of 10 billion USD, coral reefs constitute a natural barrier against flooding from hurricanes. This study spatially quantifies the risk reduction benefits of the Mesoamerican Reef in Quintana Roo for people, buildings, and hotel infrastructure. The risk reduction benefits are substantial. For example, the reefs prevented 43% additional damage during Hurricane Dean (2007) and provide nowadays hazard risk reduction for 4.3% of the people, 1.9% of the built capital, and 2.4% of the hotel infrastructure, per year. The annual benefits are estimated in 4,600 people, 42 million USD damage prevention for buildings, and 20.8 million USD for hotel infrastructure. The study also compares the risk reduction of coral reefs with (i) the protection offered by dunes and (ii) the increase in coastal risk from sea-level rise. The risk reduction of dunes is more critical where there are no coral reefs offshore and for small return-periods storms. Sea-level rise, however, will make the more frequent storms more impactful and will drive significant increases in annual expected damages across the region. However, we demonstrate that, in coral reef environments, the contribution of reef degradation to coastal risk is larger than the expected increase in risk from sea level rise. However, the spatial distribution of the risk reduction benefits from reefs differs for people and infrastructure, and in particular for hotels, which receive the most protection from reefs. Furthermore, many sections present larger benefits than the typical costs of restoration. This valuation makes a compelling case for protecting and maintaining this natural infrastructure for its risk reduction service, but also allows the development of piloting innovative strategies, such as risk finance and insurance strategies, that can align environmental and risk management goals.

In this work, we present several applications of the 2D-3D multi-domain couplings for Navier-Stokes models developed and validated in its companion (Di Paolo et al., submitted). The methodology is used to carry out some relevant simulations which include long regular and irregular waves, solitary wave propagation on a shallow foreshore, focused wave group transformation on a planar beach, wave impact on a cylinder and finally, the numerical twin of a complex laboratory experiment to analyse the performance of a perforated breakwater under wave action. Results agree well with the full 3D simulations and laboratory experiments and demonstrate the feasibility of using the 2D-3D coupled methodologies presented in Part I to successfully replace full 3D modelling. For all the cases considered, the application of coupled methodologies have resulted in a drastic reducing of the computational time without decreasing the accuracy of the full solution.

A regression-guided classification is implemented in statistical downscaling models based on weather types for downscaling multivariate wave climate and modelling extreme events. The semi-supervised method classifies the atmospheric circulation conditions (predictor) and the estimations from a regression model linking the circulation with local marine climate (filtered predictand). A weighted factor controls the influence of the predictor and predictand in the weather patterns to improve the performance of the classification to reflect local marine climate characteristics. In addition to the analysis of the variance explained by the predictor and the predictand, the selection of the optimal value of the weighted factor is based on the predictand response in order to avoid subjectivity in the solution. The statistical models using the guided classification are applied in the North Atlantic. The new technique reduces the dispersion of the multivariate predictand within weather types and improves the model skill to downscale waves and to reproduce extremes.

Focused on offshore wind energy operation and maintenance applications, this work presents a detailed accessibility analysis of the North Sea. After a review of existing normative dedicated to inspection and access of offshore wind turbines, a rigorous mathematical formulation of relevant accessibility parameters is given by means of the set theory. Long-term and high-resolution metocean data are extracted from reanalysis databases and used to evaluate spatial and temporal variability of such parameters. Respectively restricted by significant wave height and mean wind speed, access by workboat and helicopter is evaluated. Being affected by both wave height and wind speed. Access by offshore crane is also analyzed. It resulted that the UK coast and the southern region of the North Sea are highly accessible, while the coast of Denmark and Norway undergoes more severe metocean conditions. This is, however, balanced by a higher wind resource. Moreover, a strong seasonality is ascertained, together with a drastic reduction of accessibility during daytime in a vast part of the basin. Accessibility during daytime in winter and autumn is very difficult for the whole North Sea. Among the studied farms, Dogger Bank is by far the one with the highest resource and lowest accessibility, while Thorntonbank III the one with the lowest resource and highest accessibility. In addition, accessibility is non-linearly related to wind speed and wave height limits chosen for the access strategies covered. Copyright © 2016 John Wiley & Sons, Ltd.

Offshore wind energy is moving towards a future where the main challenge is to cope with the increasing water depth needed to access more and better wind resources. One of the first steps to be undertaken is the development of floating structures to support either wind turbines or measurement devices for the proper characterization of wind energy resources. The use of floating devices for measuring wind speed involves a number of uncertainties not presented by seabed fixed systems. These sources of uncertainty or error are present both in instantaneous wind measurements and averaged (10 min or hourly) values because of (i) variability in the measurement height, (ii) the tilt of the anemometer and (iii) the relative velocity between the anemometer and the wind, among others. In this paper, a methodology for assessing the error in the wind measurement characterization because of the movement of a floating meteorological mast is presented. By the numerical simulation of a floating mast, the short- and long-term error in the characterization of the wind at different heights has been evaluated. In general, the error because of the tilt can reach up to 80% of the total error; the error because of the variation of the vertical position of the anemometer reaches values of up to 15% in some cases; moreover, the error associated with the relative velocity between the anemometer and the wind, for averaged values, is significantly less. Finally, it can be concluded that the total error is lower than 0.5% for 10 min averaged wind speed of up to 24 m/s. Copyright © 2016 John Wiley & Sons, Ltd.

Based on energy conservation a new analytical formulation for the evaluation of wave damping under the combined effect of waves and both following and opposing currents is presented. The formulation obtained for regular and random waves allows the derivation of analytical expressions for the vegetation drag coefficient as a function of wave damping parameters. These parameters are calibrated using a unique experimental set obtained in a large-scale wave basin considering the interaction of waves and currents with real vegetation representative of salt marshes, namely Spartina anglica and Puccinellia maritime. Comparisons show the quality of the analytical formulation under different hydrodynamic conditions, vegetation species and various Reynolds numbers formulated in terms of plant characteristics such as the deflected plant length accounting for the flow-induced bending of the vegetation. The new formulation can be useful to be implemented in phase averaged and phase resolving numerical models of wave propagation.

This paper presents an innovative vertical breakwater cross-section integrating an overtopping wave energy converter, named OBREC-V, and the analysis of its hydraulic performance and stability response to hydraulic loading. The structure is composed of a vertically-faced caisson with a sloping ramp on the top, a reservoir and a set-back crown-wall. The analysis of the structure is carried out by performing numerical simulations based on the Volume-Averaged Reynolds Averaged Navier-Stokes (VARANS) equations. The numerical simulations are performed to compare the performance of a traditional and innovative vertical caissons under the action of irregular waves, in terms of wave reflection, overtopping and wave acting forces. Results show that the reflection coefficients are lower than those computed in front of the traditional breakwater, with a reduction of up to the 40%. New formulations are proposed to better estimate the reflection coefficient and the wave overtopping at the rear side of the structure taking into account the non-conventional geometry of the device. The analysis of the forces indicate that the non-conventional geometry of the innovative OBREC-caisson increases the overall stability of the structure. The values of the safety factor against sliding, Cs, on innovative caissons are similar or greater than those calculated on the traditional vertical structure for almost all the tests. The downward force on the ramp and reservoir and the time lag between the vertical and horizontal forces, lead to a significant reduction of the maximum destabilizing forces Fs in the innovative breakwater, whose values range between 60 and 80% of the ones computed on the traditional structure. The obtained results show the co-benefits, in terms of functionality and hydraulic stability, that an OBREC-V entails with respect to a traditional vertical breakwater.

Climate change is and will continue altering the world's coasts, which are the most densely populated and economically active areas on earth and home for highly valuable ecosystems. While there is considerable relevant research, in the authors' experience this problem remains challenging for coastal engineering. This paper reviews important challenges in this respect and identifies three key actions to address them: (a) refocusing traditional practice towards more climate-aware approaches; (b) developing more comprehensive risk frameworks that include the multi-dimensionality and non-stationarity of their components and consideration of uncertainty; and (c) building bridges between risk assessment and adaptation theory and practice. We conclude that the way forward includes numerous activities including increased observations; the attribution of coastal impacts to their drivers; enhanced climate projections and their integration into impact models; more impact assessments at the local scale; dynamic projections of spatially-distributed exposure and vulnerability; and the exploration of inherently adaptive options. Given the complexity of the possible solutions, more practical guidance is required.

In a context of growing concern about climate change and its potential consequences for coastal systems, adaptation is becoming more important than ever before. This paper presents a national planning framework for adaptation to climate change, which is pioneer in the field as it is multi-sectoral and focuses specifically on coastal areas, pursuing the safety of their communities in an uncertain future. The strategy is statutory as it emanates from the new Spanish Coastal Law, which in addition to many other implications includes the compulsory development of a Spanish Strategy for Coastal Adaptation to Climate Change (SSCACC) and its submission to Strategic Environmental Assessment. This paper covers the fundamental aspects of both the SSCACC and the accompanying Strategic Environmental Study, providing recommendations on the assessment of coastal risks triggered by climate change and extreme events, adaptation and risk reduction planning and implementation, and monitoring. Additionally, this work gives insight into the wide-ranging consultation process carried out prior to the SSCACC's approval and the stakeholders involved, and how the SSCACC handles climate change uncertainty and struggles for overcoming barriers.

This work represents the first attempt to study the behavior of sea level extreme events nearshore using satellite altimetry data. A novel approach based on the application of a nonstationary extreme model to nontidal residual monthly maxima from remote data is presented. With the aim of countering the lack of accuracy, an extreme scale factor to correct satellite data is defined. The extreme scale factor depends on local morphology and its definition makes use of the information provided by 14 tide gauges along the North American East Coast. The methodology is validated using eight additional tide gauge records along the study region. Low differences on values associated to high return periods using satellite and tide gauge data input are found for all the validated locations. Besides, a regional study of the climate variability of extreme sea levels from satellite is also presented. The found climate patterns strongly agree with the historical climate variations from in situ data. Results show a great potential of this approach, especially at those locations where in situ information is not available. The work reported here was partially supported by the Spanish Government through the grant PORTIO (BIA2015-70644-R); project ECLISEA, part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by UC-IHC, HZG, BRGM, NCSRD, and CNRS and cofunding by the European Union (Grant 690462), and the US DOD Strategic Environmental Research and Development Program (SERDP Project RC-2644).

Coral reefs can provide significant coastal protection benefits to people and property. Here we show that the annual expected damages from flooding would double, and costs from frequent storms would triple without reefs. For 100-year storm events, flood damages would increase by 91% to $US 272 billion without reefs. The countries with the most to gain from reef management are Indonesia, Philippines, Malaysia, Mexico, and Cuba; annual expected flood savings exceed $400 M for each of these nations. Sea-level rise will increase flood risk, but substantial impacts could happen from reef loss alone without better near-term management. We provide a global, process-based valuation of an ecosystem service across an entire marine biome at (sub)national levels. These spatially explicit benefits inform critical risk and environmental management decisions, and the expected benefits can be directly considered by governments (e.g., national accounts, recovery plans) and businesses (e.g., insurance)., Coral reefs provide significant coastal protection from storms but they have experienced significant losses. Here the authors show that the annual damages from flooding would double globally without reefs and they quantify where reefs provide the most protection to people and property.

To estimate coastal risk it is necessary to integrate the joint probability density function, including extremes, of the sea condition variables over a function that defines the consequences, typically economic damage. The use of Monte Carlo methods is common practice to undertake this integration; however, it can introduce a high computational burden for use in practical applications. Hence, a simplifying assumption of full dependence between the sea condition variables is often made. This paper describes a method that overcomes this simplifying assumption through the use of two techniques. A hybrid emulator of the simulating waves nearshore model is used to increase the computational efficiency associated with the wave transformations. In addition, a computationally efficient dynamic inundation model has been incorporated to further reduce the computational burden. To demonstrate the system, it has been applied to an urban coastal area located in northern Spain.

The aim of this paper is to provide a methodology to assess flooding risk associated to the combination of extreme flooding levels driven by Tropical Cyclone (TCs) and relative sea level rise (RSLR). The approach is based on the risk conceptual framework where the hazard, exposure, and vulnerability are defined and combined to address flooding socioeconomic consequences in Port of Spain for present and future climate (RCP8.5 in 2050). Hazard and flooding impact are assessed using a combination of statistical methods and dynamical simulations, together with a high resolution Digital Elevation Model (DEM). Combining flooding maps, exposure databases and vulnerability damage functions we have evaluated socioeconomic consequences in terms of affected population and economic damage. Besides, we have quantified the uncertainty in the results coming from the sea level rise projections and vulnerability information. The application of the methodology indicates increasing flooding threat for the future climate that could exacerbate economic losses in case of inaction. The expected annual damage (EAD) in present climate is 12.24 MUSD while in 2050 it will reach 15.22 [14.88- 15.67] MUSD. This paper comes out from the project “Port of Spain Probabilistic Hazard and Vulnerability Assessment based on Climate Change Projections” funded by the Inter-American Development Bank (IDB). We acknowledge the World Climate Research Programme's Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modelling groups for producing and making available their model output.

Coastal communities throughout the world are exposed to numerous and increasing threats, such as coastal flooding and erosion, saltwater intrusion and wetland degradation. Here, we present the first global-scale analysis of the main drivers of coastal flooding due to large-scale oceanographic factors. Given the large dimensionality of the problem (e.g. spatiotemporal variability in flood magnitude and the relative influence of waves, tides and surge levels), we have performed a computer-based classification to identify geographical areas with homogeneous climates. Results show that 75% of coastal regions around the globe have the potential for very large flooding events with low probabilities (unbounded tails), 82% are tide-dominated, and almost 49% are highly susceptible to increases in flooding frequency due to sea-level rise. A.R., F.J.M. and P.C. acknowledge the support of the Spanish ‘Ministerio de Economia y Competitividad’ under Grants BIA2014-59643-R and BIA2015-70644-R. This work was critically supported by the US Geological Survey under Grant/Cooperative Agreement G15AC00426 and from the US DOD Strategic Environmental Research and Development Program (SERDP Project RC-2644) through the NOAA National Centers for Environmental Information (NCEI). Dynamic atmospheric corrections (storm surge) are produced by CLS Space Oceanography Division using the Mog2D model from Legos and distributed by Aviso, with support from CNES (http://www.aviso.altimetry.fr/). Marine data from global reanalysis are provided by IHCantabria and are available for research purposes upon request at ihdata@ihcantabria.com.

Wave climate characterization at different time scales (long-term historical periods, seasonal prediction, and future projections) is required for a broad number of marine activities. Wave reanalysis databases have become a valuable source of information covering time periods of decades. A weather-type approach is proposed to statistically downscale multivariate wave climate over different time scales from the reanalysis long-term period. The model calibration is performed using historical data of predictor (sea level pressure) and predictand (sea-state parameters) from reanalysis databases. The storm activity responsible for the predominant swell composition of the local wave climate is included in the predictor definition. N-days sea level pressure fields are used as predictor. K-means algorithm with a postorganization in a bidimensional lattice is used to obtain weather patterns. Multivariate hourly sea states are associated with each pattern. The model is applied at two locations on the east coast of the North Atlantic Ocean. The validation proves the model skill to reproduce the seasonal and interannual variability of monthly sea-state parameters. Moreover, the projection of wave climate onto weather types provides a multivariate wave climate characterization with a physically interpretable linkage with atmospheric forcings. The statistical model is applied to reconstruct wave climate in the last twentieth century, to hindcast the last winter, and to project wave climate under climate change scenarios. The statistical approach has been demonstrated to be a useful tool to analyze wave climate at different time scales. The work was partly funded by the project iMar21 (CTM2010-15009) from the Spanish Government and the FP7 European projects CoCoNet (287844) and Mermaid (288710).

This work presents a new model for wave and submerged vegetation which couples the flow motion with the plant deformation. The IH-2VOF model is extended to solve the Reynolds Average Navier–Stokes equations including the presence of a vegetation field by means of a drag force. Turbulence is modeled using a k–e equation which takes into account the effect of vegetation by an approximation of dispersive fluxes using the drag force produce by the plant. The plant motion is solved accounting for inertia, damping, restoring, gravitational, Froude–Krylov and hydrodynamic mass forces. The resulting model is validated with small and large-scale experiments with a high degree of accuracy for both no swaying and swaying plants. Two new formulations of the drag coefficient are provided extending the range of applicability of existing formulae to lower Reynolds number.

The mathematical modeling of the interaction of water waves with porous coastal structures has continuously been among the most relevant challenges in coastal engineering research and practice. Finding a tool to better predict essential processes, relevant to the functionality and stability of breakwaters and jetties, and how they are affected by permeability, has been hampered by computational limitations that are being overcome. Over the last 60 years, the Journal of Waterway, Port, Coast, and Ocean Engineering has witnessed gradual developments leading from linearized solutions based on wave theories and constant friction coefficients to very sophisticated Eulerian or Lagrangian solvers of the Navier-Stokes (NS) equations, including turbulence within porous media. Today, although not without difficulty, the first steps are being made toward addressing the simulation of a fully three-dimensional interaction of complete sea states with porous structures at prototype scale. In this paper, after po...

Over the last decades, population densities in coastal areas have strongly increased. At the same time, many intertidal coastal ecosystems that provide valuable services in terms of coastal protection have greatly degraded. As a result, coastal defense has become increasingly dependent on man-made engineering solutions. Ongoing climate change processes such as sea-level rise and increased storminess, require a rethinking of current coastal defense practices including the development of innovative and cost-effective ways to protect coastlines. Integrating intertidal coastal ecosystems within coastal defense schemes offers a promising way forward. In this perspective, we specifically aim to (1) provide insight in the conditions under which ecosystems may be valuable for coastal protection, (2) discuss which might be the most promising intertidal ecosystems for this task and (3) identify knowledge gaps that currently hamper application and hence need attention from the scientific community. Ecosystems can contribute most to coastal protection by wave attenuation in areas with relatively small tidal amplitudes, and/or where intertidal areas are wide. The main knowledge gap hampering application of intertidal ecosystems within coastal defense schemes is lack in ability to account quantitatively for long-term ecosystem dynamics. Such knowledge is essential, as this will determine both the predictability and reliability of their coastal defense function. Solutions integrating intertidal ecosystems in coastal defense schemes offer promising opportunities in some situations, but require better mechanistic understanding of ecosystem dynamics in space and time to enable successful large-scale application. © 2013 Elsevier B.V.

In this work, it is evaluated the accessibility of a floating platform, by means of a catamaran vessel equipped with a fender. The two bodies are modelled as a constrained multi-body system in the frequency domain. Transfer functions are calculated for the motions and forces of the system. Access is possible when no slip conditions occur at the fender, and when the relative rotations between the two bodies are within certain tolerance limits. Four response variables are defined to impose such conditions. In a short-term sea state the extreme maximum crest height of these variables is computed, assuming that response crest heights follow a Rayleigh distribution. Each of the extreme values is compared to a specific threshold, to determine whether access is possible or not. Accessibility is calculated for a sample platform located off the coast of Scotland using hindcast data for the period 1980-2013. Average accessibility resulted to be 23.7%. A strong seasonality is ascertained, together with a large variation of accessibility, due to the variability of wave climate. The authors would like to acknowledge the projects “OceaNET”, which received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 607656, and “Plataformas multiuso para aplicaciones offshore” of the University of Cantabria (code: 56.JS05.64061).

The present study shows a methodology to carry out a comprehensive study of port agitation and resonance analysis in Geraldton Harbor (Western Australia). The methodology described and applied here extends the short and long wave hindcast outside the harbor and towards the main basin. To perform such an analysis, and as the first stage of the methodology, it is necessary to determine, in detail, both the long and short wave characteristics, through a comprehensive methodology to obtain and to hindcast the full spectral data (short waves + long waves, for frequencies between 0.005 and 1 Hz). Twelve-year spectral hindcast wave data, at a location before the reef, have been modified analytically to include the energy input associated with infragravity waves. A decomposition technique based on the energy balance of the radiation stress of short waves is followed. Predictions for long wave heights and periods at different harbor locations are predicted and validated with data recorded during 2004 to 2009. This new database will ensure an accurate and reliable assessment of long wave hourly data (height, period and currents) in any area within the main basin of the Port of Geraldton, for its present geometry. With this information, two main task will be completed: (1) undertake a forensic diagnosis of the present response of the harbor, identifying those forcing characteristics related to inoperability events; and (2) propose any layout solutions to minimize, change, dissipate/fade/vanish or positively modify the effects of long waves in the harbor, proposing different harbor geometry modifications. The goal is to identify all possible combinations of solutions that would minimize the current inoperability in the harbor. Different pre-designs are assessed in this preliminary study in order to exemplify the potential of the methodology.

Wind wave reanalyses have become a valuable source of information for wave climate research and ocean and coastal applications over the last decade. Nowadays, wave reanalyses databases generated with third generation models provide useful wave climate information to complement, both in time and space, the instrumental measurements (buoys and alimetry observations). In this work, a new global wave reanalysis (GOW) from 1948 onwards is presented. GOW dataset is intended to be periodically updated and it is based on a calibration of a model hindcast with satellite altimetry data, after verification against historical data. The outliers due to tropical cyclones (not simulated due to insufficient resolution in the wind forcing) are identified and not taken into account in the process to correct the simulated wave heights with the altimeter data. The results are validated with satellite measurements in time and space. This new calibrated database represents appropriately the wave climate characteristics since 1948 and aims to be the longest and up-to-date wave dataset for global wave climate variability analysis as well as for many coastal engineering applications.

In the last years, new tools have been developed to describe wave climate. In particular, wave hindcast models allow a very detailed description in time and space. However, the data bases generated from these models require calibration with instrumental observations. In this work, a methodology for spatial calibration of wave hindcast data bases is developed. It is based on an Empirical Orthogonal Function decomposition and a non-linear transformation of the spatial–time modes. The method is applied to monthly long-term distribution of significant wave height in the Western Mediterranean. The calibration (transformation of the modes) is carried out using existing buoys in the area. After calibration, the validation with satellite data shows that this methodology is useful to better define wave climate from hindcast data bases.

As the world's population grows to a projected 11.2 billion by 2100, the number of people living in low-lying areas exposed to coastal hazards is projected to increase. Critical infrastructure and valuable assets continue to be placed in vulnerable areas, and in recent years, millions of people have been displaced by natural hazards. Impacts from coastal hazards depend on the number of people, value of assets, and presence of critical resources in harm's way. Risks related to natural hazards are determined by a complex interaction between physical hazards, the vulnerability of a society or social-ecological system and its exposure to such hazards. Moreover, these risks are amplified by challenging socioeconomic dynamics, including poorly planned urban development, income inequality, and poverty. This study employs a combination of machine learning clustering techniques (Self Organizing Maps and K-Means) and a spatial index, to assess coastal risks in Latin America and the Caribbean (LAC) on a comparative scale. The proposed method meets multiple objectives, including the identification of hotspots and key drivers of coastal risk, and the ability to process large-volume multidimensional and multivariate datasets, effectively reducing sixteen variables related to coastal hazards, geographic exposure, and socioeconomic vulnerability, into a single index. Our results demonstrate that in LAC, more than 500,000 people live in areas where coastal hazards, exposure (of people, assets and ecosystems) and poverty converge, creating the ideal conditions for a perfect storm. Hotspot locations of coastal risk, identified by the proposed Comparative Coastal Risk Index (CCRI), contain more than 300,00 people and include: El Oro, Ecuador; Sinaloa, Mexico; Usulutan, El Salvador; and Chiapas, Mexico. Our results provide important insights into potential adaptation alternatives that could reduce the impacts of future hazards. Effective adaptation options must not only focus on developing coastal defenses, but also on improving practices and policies related to urban development, agricultural land use, and conservation, as well as ameliorating socioeconomic conditions.

Coastal floodplains are complex regions that form the interface between human, physical and natural systems. This paper describes the development, application and evaluation of a conceptual foundation for quantitative integrated floodplain risk assessments using the recently-developed SPR systems model. The SPR systems model is a conceptual model that combines the well-established Source–Pathway–Receptor (SPR) approach with the concept of system diagrams. In comparison to the conventional approach, the systems model provides spatially explicit quasi-2D descriptions of the floodplain in terms of constituent elements and possible element linkages. The quasi-2D SPR, as it will henceforth be referred to in this paper, is not the final product of this work, but is an important intermediate stage which has been pursued as part of a wider European flood risk project THESEUS (www.theseusproject.eu). Further research is currently on-going to provide full quantification of the quasi-2D SPR, and to add further refinements such that hydraulic assessments could follow on easily and rapidly from the results of these appraisals. The first part of the paper synthesises current conceptual treatment of coastal floodplains and identifies areas for improvement in describing coastal floodplains as complex systems. The synthesis demonstrates that the conceptual foundation of a ‘typical’ flood risk study often achieves a less comprehensive and integrated description of the floodplain than the quantitative models which it informs. From this synthesis, the quasi-2D SPR is identified as a more robust and informative conceptual foundation for an integrated risk assessment. The quasi-2D SPR has been applied to seven European coastal floodplains as part of the THESEUS project. The second part of the paper discusses in detail the application of the quasi-2D SPR to three contrasting floodplain systems — an estuary, a coastal peninsula and a mixed open coast/estuary site. The quasi-2D SPR provides a consistent approach for achieving comprehensive floodplain descriptions that are individual to each coastal floodplain. These are obtained through a robust, participatory model-building exercise, that facilitates developing a shared understanding of the system. The constructed model is a powerful tool for structuring and integrating existing knowledge across multiple disciplines. Applications of the quasi-2D SPR provide key insights into the characteristics of complex coastal floodplains — insights that will inform the quantification process. Finally, the paper briefly describes the on-going quantitative extension to the quasi-2D SPR. ispartof: Coastal Engineering vol:87 pages:15-31 status: published