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A methodology to estimate wave-induced coastal flooding hazard maps in Spain
Journal of Flood Risk Management
Abstract
The purpose of the European Flooding Directive (2007/60/CE) is to establish a European framework for the assessment and management of flood risks. The aim is to reduce the adverse flooding consequences on a wide range of topics such as human health, environmental and cultural heritage, and economic activity. In Spain, coastal zone flood hazard and risk maps are managed by the Environment Spanish Ministry (MAGRAMA, Dirección General para la Sostenibilidad de la Costa y el Mar). These maps are designed using the methodology explained in this paper. This methodology allows to perform quick flood hazard maps along the Spanish coast, due to the combination of high-resolution marine climate databases, state-of-the-art numerical models, innovative data mining techniques, and statistical models.
... In the next section, we describe the methodology and the two data sets used for this study: for the development of the model, a large profile data set of Spanish beaches (Tom as et al., 2015) with a large spatial coverage that encompasses the entire range of beach modal states, and for the validation of the model, a long-term data set from Narrabeen Beach in Eastern Australia (Turner et al., 2016). The equation is then presented, described and tested. ...
... The profile database used for this study was obtained from a large profile database composed of Digital Terrain Models developed by IGN (the Spanish Geographical National Institute) and collected during the IOLE project (Tom as et al., 2015). The DTMs were obtained from LIDAR surveys covering the entire Spanish coast, and the dates of the survey flights are known and comprise dates from 2009 to 2012. ...
... They display a configuration that correlates accordingly to mean wave conditions at the beachfront around the date of the survey, i.e., the dry beach profile must present some sort of average shoreface profile cross section (Pilkey et al., 1993). For further information regarding the profiling, readers may refer to Tom as et al. (2015). ...
Predictions of dry beach morphologies are extensively required in coastal research for multiple purposes -e.g., dune erosion forecasting, inundation heights determination and beach fill design optimization. In this paper, we introduce and test a parametric model that describes the equilibrium shape of the dry beach in the cross-shore direction, i.e., an equation for the dry beach equilibrium profile. The model consists of a three-parameter equation formed by two terms: an exponential that defines the foreshore and berm morphology, plus a linear term that defines the slope from the berm to the landward limit as a planar far field behaviour. The three morphological parameters that shape the equation are related to the nearshore wave climate (Hs and Tp) and the sediment characteristics (d50) in a form which is consistent with previous knowledge of dry beach morphodynamics, thus proposing the runup driver and the dimensionless fall velocity Ω as the fundamental variables defining the equation parameters. We tested the predictive capacity of the model against an independent data set from Narrabeen Beach, which, depending on longshore location and the time of year, offers beach modal states ranging from dissipative to reflective. The exponential term of the equation correctly explains the foreshore and berm morphology under mean wave climate, and the linear term predicts the slope of the asymptotic-planar segment, all with good correlation coefficients (∼0.95) between modelled cross-shore transects and observations. The proposed model helps in defining the main shapes of subaerial beach profiles over the long term and it may also be useful as a coastal management tool for predicting dry beach morphologies.
... Cluster analysis refers to a series of data analysis techniques which can be used to classify large datasets into meaningful groups. The techniques have been used successfully for wave climate reduction (Camus et al., 2011;Mortlock and Goodwin, 2015;Olij, 2015; ?), morphological classification (Costa et al., 2016;Duce et al., 2016;Tomás et al., 2015), and identifying tropical cyclone trajectories (Camargo et al., 2007a,b). ...
... For post-processing, it could be used to identify patterns or to develop multiple regressions for different wave regimes. Tomás et al. (2015) developed a flood risk assessment framework for the Spanish coast. They use the Stockdon et al. (2006) equations to estimate runup for each profile along the entire coastline. ...
... The dimensionless 5 109 profiles are then converted back into real profiles which the numerical model can use. In reducing their required number of simulations by a factor of O(1000), Tomás et al. (2015) demonstrate the usefulness of cluster analysis for aggregating large morphological datasets. A similar approach could be taken for coral reefs if sufficient data becomes available. ...
Low-lying tropical islands are highly vulnerable to the effects of sea-level rise and climate change. Most pressing is the threat posed to their fresh water supplies by wave-induced flooding. This thesis attempts to generalize previous site-specific studies of flooding on coral atolls and apply it in a framework that can be used for early warning systems or long-term climate change impact studies. To do so, a large synthetic database of representative reef properties and hydrodynamics was developed using the numerical wave model XBeach, and then analyzed using a Bayesian probabilistic network. The resulting tool allows us to make real-time flood predictions based on offshore wave or sea level conditions, and the unique characteristics of a given island (e.g. topography). Narrow, smooth reefs with steep fore reef slopes are the most vulnerable to runup. Extreme flooding is associated with anomalously high, resonant low frequency waves, which are more likely to occur on narrow, smooth reefs subjected to extreme swell waves (large wave heights with long periods). These extreme swells are "blue sky" events which originate from distant storms. Thus, they may thus arrive without warning, since they are completely independent of local weather conditions. This bolsters the need for more effective prediction tools. Validation of the results presented in this study is limited by the small number of field observations against which the model can be compared. Thus, there is a need to develop a comprehensive database of reef morphology and hydrodynamics. Offshore wave conditions, water levels, and reef width are the most essential variables for predicting runup, so future research efforts should be directed towards collecting those data. This model can also be used to ask questions like, "which islands will be most severely impacted by climate change?", or "can we increase flood resilience for a given island by restoring its coral reefs?". Hence, there is also potential for its use in guiding decision-makers to allocate limited funding in the places where it will have the most impact.
... Swash on a beach can be of higher frequencies, those of incident frequency band (0.05 Hz to 0.5 Hz) or at lower frequencies of infragravity frequency band (0.003 Hz to 0.05 Hz) [3,4]. During extreme storms, wave runup often coincides with high tides and high surge levels, which increase still water level, SWL, resulting in coastal flooding, berm overtopping, and significant morphological changes to the beachface [3,[5][6][7][8][9]. ...
Most empirical equations used for wave runup predictions have been developed from measurements at straight sandy beaches in unlimited fetch environments. While there are empirical equations to predict wave runup on gravel beaches, they have not been tested for prediction of wave runup on pocket gravel beaches, in limited-fetch environment, which can be found around Mediterranean. This paper addresses this lack of measurements on this type of beaches and examines the alongshore variability of wave runup. Wave runup measurements were made using video observations along 3 cross-sectional profiles on the pocket beach of Ploče, Croatia. The measurements have shown that the wave runup can vary for about 71% even around the centerline of the pocket beach. This variability is due to beach orientation and alignment of beach profiles to the prevailing wave direction, as well as difference in beach slope. Comparison of wave runup predictions from five well-known empirical equations and field measurements showed significant underprediction (up to NBIAS = −0.33) for energetic wave events, and overall high scatter (up to NRMSE = 0.38). The best performing wave runup equation was used for further refinement outside the original parameter space by including the Goda wave peakedness parameter (Qp). The newly developed empirical equation for wave runup reduced the NBIAS to 0 and the NRMSE by 31% compared to the original equation (developed equation metrics: R = 0.91, NBIAS = 0, NRMSE = 0.2, HH = 0.2 on the study site). This empirical equation can potentially be used for design of coastal structures and artificial beaches in similar environments, but further measurements are needed to test its applicability to a range of forcing and environmental conditions.
... A good agreement is found between the vertical runup values calculated with the empirical formulation by Stockdon et al. (2006) and those computed with XBeach, see Fig. 10. Among different runup formulations that have been proposed during the last decades (Atkinson et al., 2017;Passarella et al., 2018a), we have chosen to apply the Stockdon et al. (2006) formulation due to its wide diffusion within the coastal engineering community (Tomas et al., 2016;Cohn and Ruggiero, 2016). Although empirical formulations still lack to address the effects Fig. 13. ...
This paper reports a scientific inquiry carried out within the management process of an exceptional accumulation of reeds and seagrasses that took place in December 2019 on Poetto beach (Cagliari, southern Sardinia, western Mediterranean). The magnitude of the event raised concern within the local community and tourism service providers especially for the compromised beach accessibility caused by this large amount of biomass. The scientific inquiry is carried out in support of coastal management, to assess the berm processes before the removal of the reed wracks decided by the local municipality. By means of a numerical approach, this work devotes special attention to the runup induced by storms in the presence of reed and seagrass deposits on a low-lying backshore. Field surveys reported relatively large conductivity parameters in the presence on reed and seagrass deposits. The numerical approach shows that the increased beach permeability can eventually mitigate coastal flooding induced by storms. These results highlight the ecosystem services provided by reed and seagrass wracks together with the implications for coastal protection and management.
... Previous large-scale studies have also pointed out the need of using dynamic flood modelling, in contrast with passive or simplified flood methods (for example, bathtub approach) that may cause large errors (for example, estimated in 35-54% for Hawaii 81 ). Regional coastal flood models have also relied on process-resolving cross-shore hydrodynamics with similar transect spacing (100 m) and model set-ups 81,83,84 . Although these studies do not assess the sensitivity to flood model transect spacing, it is one factor that can affect the flood risk results. ...
Habitats, such as coral reefs, can mitigate increasing flood damages through coastal protection services. We provide a fine-scale, national valuation of the flood risk reduction benefits of coral habitats to people, property, economies and infrastructure. Across 3,100 km of US coastline, the top-most 1 m of coral reefs prevents the 100-yr flood from growing by 23% (113 km²), avoiding flooding to 53,800 (62%) people, US2.6 billion (49%) in indirect economic effects. We estimate the hazard risk reduction benefits of US coral reefs to exceed US10 million km–1, whereas US reefs critically reduce flooding of vulnerable populations. This quantification of spatial risk reduction can help to prioritize joint actions in flood management and environmental conservation, opening new opportunities to support reef management with hazard mitigation funding.
... Predicting wave runup (R), defined as the maximum elevation of shoreline oscillations caused by waves, has been a subject of great interest to coastal engineers and coastal managers. Runup is an important component of coastal flooding, especially during extreme storm events when energetic waves are combined with high tidal and surge levels (Alegria-Arzaburu and Masselink, 2010;Coco et al., 2014;Gomes da Silva et al., 2016;Tomás et al., 2016). Runup also plays an essential role in sediment transport, connecting the sub-aerial and submerged beach profile (e.g. ...
Wave runup is one of the most critical parameters contributing to coastline flooding and shoreline change. Many formulas have been developed to empirically predict wave runup characteristics. However, large errors are still associated to these estimates feeding a debate on the best approach to describe runup through simple parameterizations. In this work we present a comprehensive review on runup, setup and swash empirical models. We use a large database of field measurements to verify the predictive capability of recent formulas, addressing possible sources of variability. We identify the effect of the nearshore bathymetry as an important factor missing in empirical predictors and examine this issue through an analysis of runup simulated with the SWASH model over different barred and linear bathymetries. The details of the submerged beach profile affect estimates, especially with respect to setup values. The lack of standardization in measuring, post-processing and sharing runup data, limits the application of previous published databases on new analysis. We list a set of recommendations that can be used as guidelines for new measurements to broaden the applicability of the datasets in future studies. Finally, we discuss the remaining questions that still need to be further explored.
... The European Union (EU) Floods Directive (EC, 2007) instructs management groups to prepare flood hazard maps for events of given probabilities of occurrence. Thus, the scientific community has developed multiple methodologies to assess storm-induced inundation through a variety of estimators (e.g., Ciavola et al., 2011b;Ciavola, Ferreira, Haerens, Van Koningsveld, & Arm- aroli, 2011a;Sallenger, 2000;Stockdon, Sallenger, Holman, & Howd, 2007;Tomás et al., 2016;Van Dongeren et al., 2018). Hazard-describing variables of multiple complexities can be used in inundation assessments to provide answers at both regional and local scales. ...
Hazard assessment is one of the key elements to be included in any coastal risk assessment framework. Characterizing storm-induced erosion and inundation involves the assessment of the coastal response under the forcing of a stochastic source (the storm), acting on a variable morphology (the beach) and inducing some damages. Hazard assessment under any present or future scenario will be affected by uncertainties either associated to the models used, the definition of climate conditions, and the characterization of the coastal morphology. In this context, Bayesian Networks (BN) can effectively address the problem as they allow accounting for these uncertainties while characterizing stochastically the system response and giving insight on the dependencies among involved variables. In this work, a BN-based methodology for storm-induced hazard assessment at regional scale is presented. The methodology is able to account for uncertainties associated with included models and forcing conditions through Monte-Carlo simulations. It produces distributions of erosion and inundation hazards under given scenarios allowing conditioned hazard assessments as a function of storm and morphological variables. Results are compared to hazards evaluated using an existing Coastal Risk Assessment Framework (CRAF), at two locations of the Catalan coast already identified as hotspots for storm-induced erosion and/or flooding.
... The European Union (EU) Floods Directive (EC, 2007) instructs management groups to prepare flood hazard maps for events of given probabilities of occurrence. Thus, the scientific community has developed multiple methodologies to assess storm-induced inundation through a variety of estimators (e.g., Ciavola et al., 2011b;Ciavola, Ferreira, Haerens, Van Koningsveld, & Armaroli, 2011a;Sallenger, 2000;Stockdon, Sallenger, Holman, & Howd, 2007;Tomás et al., 2016;Van Dongeren et al., 2018). Hazard-describing variables of multiple complexities can be used in inundation assessments to provide answers at both regional and local scales. ...
Coastal flood risk assessment requires a reliable estimation of the frequency of inundation hazards, that is, characterizing the hazard magnitude and assigning a probability of occurrence. In this work we analyse the uncertainty introduced in the assessment associated to the method to assign the probability of occurrence to coastal flood hazards. To this end we have compared the use of two general methods, the response and the event approaches. Different procedures are used to characterize coastal inundation hazards depending on the analysis scale and data availability. Thus, a range of possibilities has been analysed, from simple estimators such as run‐up to modelled flood‐prone areas. The analysis has been performed for all wave and water level conditions around the Spanish coast. The results show that the differences between the methods are location‐dependent, and thus, determined by the exposure to wave and water level conditions. When using the event approach, the run‐up or total water level (with good correlation between waves and surge) distributions reasonably approximate those of the response approach with low associated uncertainty. When the assessment aims to output overtopping discharges or inundation maps, observed differences suggest that the event approach would produce misleading conclusions in inundation‐related coastal management and decision‐making. This article is protected by copyright. All rights reserved.
... At the regional scale, such general predictions are affected by many factors, such as isostatic adjustment [5] and sea ice shrinking [6]. Wave climate is generally excluded from long-term extreme water level analyses, but its effect on coastal flooding is well documented [7][8][9][10]. Depending on the location, a changing wave climate at the interannual-to-multidecadal scales is likely to either greatly damper or increase the total water level at the coast [11]. ...
Coastal management often relies on large-scale flood mapping to produce sea level rise assessments where the storm-related surge is considered as the most important hazard. Nearshore dynamics and overland flow are also key parameters in coastal flood mapping, but increase the model complexity. Avoiding flood propagation processes using a static flood mapping is less computer-intensive, but generally leads to overestimation of the flood zone, especially in defended urban backshore. For low-lying communities, sea level rise poses a certain threat, but its consequences are not only due to a static water level. In this paper, the numerical process-based model XBeach is used in 2D hydrodynamic mode (surfbeat) to reproduce an observed historical flood in Maria (eastern Canada). The main goal is to assess the impacts of a future storm of the same magnitude in the horizon 2100 according to an increase in sea level rise. The model is first validated from in situ observations of waves and water levels observed on the lower foreshore. Based on field observations of a flood extent in 2010, the simulated flooded area was also validated given a good fit (59%) with the actual observed flood. Results indicate that the 2010 storm-induced surge generated overwash processes on multiple areas and net landward sediment transport and accumulation (washover lobes). The flood was caused by relatively small nearshore waves (H s < 1 m), but despite small water depth (>1.2 m), high flow velocities occurred in the main street (U > 2 m/s) prior to draining in the salt marsh. The impact of sea level rise on the low-lying coastal community of Maria could induce a larger flood area in 2100, deeper floodwater, and higher flow velocities, resulting in higher hazard for the population.
... Medium tidal range (Rt, m), as a hydrodynamic characteristic, was gathered from the C3E Viewer (Menéndez et al., 2014). Morphological characteristics were gathered for each marina: area (A, m 2 ) was calculated by digitalizing the 320 polygons and calculating the area using the "calculate geometry" tool of ArcGIS software (Gómez et al., 2017); length (L, m) was calculated with the "minimum bounding geometry" tool of ArcGIS software (Gómez et al., 2017); entrance width (e, m) was calculated using ArcGIS techniques; depth (H, m) was obtained from the official web site of each marina and the Spanish Marinas Federation web site (FEAPDT, 2016); and closure depths (h*, m) were extracted from the Tomás et al. (2016) database using the "near tool" of ArcGIS software. ...
Recreational sailing sector has an impact on water quality in marinas. This study proposes a standard procedure to assess the environmental risk of marinas on water quality. Risk is assessed through integrating environmental pressures, environmental conditions and societal responses (i.e. the Pressure-State-Response model). Pressures are estimated considering the main driving forces: navigation, port, dredging and external activities. State is estimated through combining the susceptibility, the ecological value and naturalness. Response is estimated through environmental management instruments and adopted measures. Managers and authorities can hierarchically classify marinas from a multi-scale spatial framework. This tool is particularly powerful for generating local, regional or national atlases to prioritize environmental planning actions. The method is applied to 320 marinas along the Spanish coast. This implementation confirms the usefulness, versatility and adaptability of this procedure as a tool for the environmental management of marinas.
... These results are coherent with Stockdon et al. (2014), who indicated certain underestimation of Stockdon et al. (2006) empirical values for the most energetic storm conditions. Ru 2% values obtained from IH-2VOF model and the Stockdon et al. (2006) formula were compared for planar and nonplanar beaches in Tomás et al. (2015). For planar beaches, both approaches fit well, but for nonplanar beaches (i.e. 30 and 37 profiles), the IH-2VOF model is recommended instead of the Stockdon et al. (2006) formula. ...
Wave run-up is defined as the maximum vertical extent of wave up-rush on a beach or structure above the sea water level
from wave breaking. Wave run-up is responsible for beach and dune erosion and can be an important component of
coastal flooding. Run-up can be estimated using either empirical formulations or sophisticated wave-breaking models
with high computational demand. On the other hand, meta-models are efficient approximations of physical-process
models that enable researchers to obtain long-term time series of wave dynamics. These hybrid models are developed by
combining statistical techniques and numerical models. In this study, a methodology to transform offshore sea conditions
to long-term time series of wave run-up is described. The methodology combined the construction of two meta-models of
offshore wave propagation to coastal areas and of nearshore wave transformation to run-up. Clustering techniques were
then implemented to select a subset of spectral patterns of the offshore conditions for nearshore transfer and a subset of
sea states for reconstructing the run-up. Multivariate, radial-basis functions were then fitted to the outputs of the wave
propagation and wave run-up simulations to reconstruct the time series of sea-state parameters in shallow water and the
time series of run-up. This methodology was applied to Palm Beach on the Gold Coast (QLD, Australia). The nearshore
wave climate was validated quantitatively, whereas the reconstructed wave run-up and total water-level time series was
validated with a qualitative approximation, confirming that this methodology is capable of accurately transforming the
offshore wave conditions into run-up time series. The total water levels were also reconstructed to show the applicability
of the results to probabilistic flood-risk analyses.
... Models simulating overtopping are much more recent and still require substantial research developments (Hubbard and Dodd, 2002;Gallien, 2016). In the last few years, several process-based models have been developed and applied to address coastal flooding risks: VOF (volume of fluid) model (Tomás et al., 2016), Boussinesq model (Lynett et al., 2010;Andrade et al., 2013), nonhydrostatic phase-averaged model (Smith et al., 2012;Gallien, 2016), and NLSW (nonlinear shallow water) model (Suzuki et al., 2012;Guimarães et al., 2015;Le Roy et al., 2015). These, and especially the SWASH model (Simulating WAves till SHore), are able to reproduce the dynamics of wave surges and overtopping to an appropriate degree of reliability for coastal flooding studies (Suzuki et al., 2012). ...
A modelling chain was implemented in order to propose a realistic appraisal of the risk in coastal areas affected by overflowing as well as overtopping processes. Simulations are performed through a nested downscaling strategy from regional to local scale at high spatial resolution with explicit buildings, urban structures such as sea front walls and hydraulic structures liable to affect the propagation of water in urban areas. Validation of the model performance is based on hard and soft available data analysis and conversion of qualitative to quantitative information to reconstruct the area affected by flooding and the succession of events during two recent storms. Two joint probability approaches (joint exceedance contour and environmental contour) are used to define 100-year offshore conditions scenarios and to investigate the flood response to each scenario in terms of (1) maximum spatial extent of flooded areas, (2) volumes of water propagation inland and (3) water level in flooded areas. Scenarios of sea level rise are also considered in order to evaluate the potential hazard evolution. Our simulations show that for a maximising 100-year hazard scenario, for the municipality as a whole, 38 % of the affected zones are prone to overflow flooding and 62 % to flooding by propagation of overtopping water volume along the seafront. Results also reveal that for the two kinds of statistic scenarios a difference of about 5 % in the forcing conditions (water level, wave height and period) can produce significant differences in terms of flooding like +13.5 % of water volumes propagating inland or +11.3 % of affected surfaces. In some areas, flood response appears to be very sensitive to the chosen scenario with differences of 0.3 to 0.5 m in water level. The developed approach enables one to frame the 100-year hazard and to characterize spatially the robustness or the uncertainty over the results. Considering a 100-year scenario with mean sea level rise (0.6 m), hazard characteristics are dramatically changed with an evolution of the overtopping / overflowing process ratio and an increase of a factor 4.84 in volumes of water propagating inland and 3.47 in flooded surfaces.
... Algunos trabajos utilizan los valores de parámetros morfométricos conjuntamente con los parámetros ambientales para determinar patrones morfodinámicos entre las playas evaluadas (Pereira et al. 2010;Scott et al. 2011). Otros determinan perfiles "tipo", o centrales, que representen perfiles reales, con el objetivo de disminuir la cantidad de datos cuando se quiere ejecutar modelos, tal como aplicado en el cálculo del riesgo de inundación costera para toda España (Tomás et al. 2015) o en la aplicación de un modelo que evalúa el impacto de temporales sobre dunas primarias (Taylor et al. 2015). Hay también los que realizan una clasificación de los perfiles con relación a su forma, tal como utilizado por Díez et al. (2017a) en la definición de formas típicas de perfiles de playa seca y su relación con el estado morfodinámico. ...
The morphology of equilibrium foredunes profile was evaluated in this thesis. The results indicated that the size of foredunes vary significantly, however their shape is quite constant. Their morphometric parameters volume, height, width and maximum slope are highly correlated, allowing the proposition of equations (allometric relationships). Marine and wind dynamics were evaluated to determine the parameters that control the foredune equilibrium morphology: its size is related to the aeolian sediment drift potential and marine dynamic, while its location depends on the marine dynamics. Based on these results a long-term functioning model was proposed. This model explains different morphological characteristics of the foredunes in equilibrium as a function of the joint action of the marine and wind dynamics. Finally, an equilibrium foredune profile model was proposed.
... Several avenues have been explored to mitigate this problem. Inundation maps have been developed to determine the hazard and assist in planning (e.g., Dietrich et al., 2010;Fortunato et al., 2013;Bertin et al., 2014;Le Roy et al., 2015;Tomás et al., 2015;Bilskie et al., 2016;Perini et al., 2016). Forecast systems allow the anticipation of extreme events and support first responses (e.g., Zampato et al., 2016;Fortunato et al., 2017). ...
On February 15, 1941, a storm caused one of the major natural disasters in the Iberian Peninsula in the past century. The storm made landfall in the north of Portugal, leading to a large surge in the Tagus estuary. Adverse meteorological conditions combined with a high spring tide led to extensive flooding of dry land, causing severe damage and casualties. A suite of regional and local scale models is developed to analyze the event and the relative contributions of the different forcing agents to the extreme water levels. Quantitative and qualitative validations show that the models adequately reproduce this type of events. The models are then used to assess the inundation in the upstream reaches of the estuary where extensive agricultural lands are protected by dikes. Results show that over 25 km² could be inundated today, a value that would increase threefold for a sea level rise of 0.5 m. Then, the relative importance of the different forcing mechanisms on the extreme water levels is investigated through numerical experiments. It is shown that the regional surge and the setup induced by swell are the two main drivers of the inundation. In particular, the modulation of the wave setup by tides induces a semi-diurnal signal which is amplified by resonance inside the estuary.
... The profile database used for this study was obtained from a European profile database collected in IOLE, a methodology used to estimate wave-induced coastal flooding hazard maps in Spain (Tomá s et al., 2015). They obtained dry beach profiles from digital terrain models (DTMs) developed by the Spanish Geographical National Institute (IGN). ...
The dry part of the beach is probably the most extensively used part of the beach system. It comprises the zone from high tide level to the landward edge, which can be either a dynamic (dune field) or a fixed boundary (cliff, rocky ledge, or promenade). Here is presented a complete description of its morphology on the basis of the analysis of 91 study sites selected along the entire coast of Spain. The analysis comprises four different regions in terms of wave climate, geology, and tidal range, covering a wide range of coastal environments. In this study, a zonation of the dry beach profile is presented attending to the dynamics, the morphometric index, and the timescales of variation in which three different segments are defined: the foreshore segment, from the mean high water level to the berm, if present; the seasonal segment, which represents the zone between seasonal berms; and the interannual segment, which comprises the segment between the winter berm (or the most stable berm in case of no seasonality) and the landward edge of the beach. Besides, through cluster profile analysis-applying the K-Means classification algorithm to the entire data set of profiles-four types of dry beach profile are proposed, described, and related to a particular beach modal state: dissipative, intermediate, reflective, and ultradissipative. The observations and results presented here contribute to understanding the morphodynamics of the dry part of the beach and set the basis for subsequent studies concerning the equilibrium dry beach profile.
... It can also be integrated into a static flood mapping approach (Gallien et al. 2014;Didier et al. 2015), where the flood elevation is assumed to propagate toward the coast and overland until it reaches a homogeneous and equivalent contour elevation (Vitousek et al. 2009;Patrick et al. 2015). Wave runup can be calculated at different points along the coast to give a TWL at each cross-shore profile where the slope has been calculated (Tomás et al. 2015). On platform-beaches however, the morphodynamic context is different to sandy beaches. ...
Wave runup in a shore platform environment has been acquired by in situ measurements at high tide and along field debris following the December 6, 2010, flood near Rimouski (Quebec, Canada), south coast of the St. Lawrence estuary. Using offshore wave data and beach slopes, a linear empirical runup relationship has been adjusted to the study site and showed good predictive results. Two types of beach slopes, the upper foreshore and foreshore slopes, have been assessed in order to calculate the surf similarity parameter. It appears that the foreshore slope, located between the coastline and the end of the foreshore at the seaward edge of the platform, shows best results. This slope was thus used to calculate the wave runup on the shore platform. A static flood map, adding wave runup to observed peak tidal level including the storm surge during the December 6, 2010, flood, has been realized on a LiDAR base layer for a specific site in Sainte-Luce. A second flood map has been applied to validate the approach on an external site in Sainte-Flavie, outside the study area. In both cases, predicted flood extents highly correspond to observed flooded area. High underpredictions occur when using the observed storm tide level only (a 182-year event) without runup, where only 5 and 4 % of the studied area are considered as flooded, respectively. It appears that in a shore platform environment, a wider foreshore reduces wave runup and flood levels.
The Mediterranean region is a hotspot for highly interconnected climate risks with key economic sectors highly vulnerable to climate hazards (agriculture, fisheries, forestry, tourism). This reinforces the socioeconomic vulnerability of the population living in the region (Ali et al. in Climate change 2022: impacts, adaptation and vulnerability. Contribution of working group II to the sixth assessment report of the intergovernmental panel on climate change. Cambridge University Press, Cambridge, UK, pp 2233–2272, 2022). Understanding climate impacts on coastal areas is a key element for adaptation, urban planning, and economic policy. Legally, in the context of Spain, the promoters of infrastructure projects on the coastal zone are required to submit a Coastal Dynamics Study to the competent authority (National Coastal Authority). These studies must include an assessment of the potential impacts of climate change on the proposed projects, as well as potential adaptation solutions. In this paper, two case studies are presented, on one side, the study of a real estate asset (restaurant) vulnerable to coastal erosion in Tarragona that was affected by storm Celia in 2022 where authorities required a coastal dynamics study to understand future climate risks. On the other side, non-permanent tourist-related and nautical facilities in Formentera Island. The paper presents the processes followed to assess the climate risk and the results obtained to understand the needed adaptation solutions.
The subaerial zone of the beach is a highly dynamic area that supports recreation and different habitats; as such, it has been the focus of many past studies. Accordingly, this paper reports a study of the assessment of the erosion and accretion over subaerial beach profiles and their relationship to the upper beach width. To this end, the erosion and accretion balanced approach (EABA) which was initially developed for beach profiles in the offshore direction is employed and tested over 934 subaerial beach profiles from the southwestern Maine coastline in New England region of the USA. The results indicated that the calculated average profile over 14 years does represent the equilibrium profile and the model can be used for subaerial beach profiles with high accuracy. Moreover, the results verified the application of the erosion and accretion balanced approach even in natural phenomena such as strong storms and abrupt sea level rises.
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.
p>Las desembocaduras, estuarios y tramos de ríos costeros son elementos hidrodinámicamente complejos debido a la interacción de varias dinámicas generadoras de inundación como la marea astronómica, la marea meteorológica, el oleaje y el caudal del río, entre otras. La marea astronómica es una onda larga que se propaga aguas arriba llegando a afectar a tramos de río situados a decenas de kilómetros de la costa. En estos tramos de río, el mismo nivel del agua puede ser el resultado de diferentes combinaciones de las dinámicas mencionadas. Los estudios de peligrosidad y riesgo de inundación en tramos de ríos afectados por la marea se han basado hasta ahora en la aplicación de una condición de contorno de nivel de marea fijada de forma más o menos arbitraria. En España, la Guía metodológica para el desarrollo del Sistema Nacional de Cartografía de Zonas Inundables (Ministerio de Medio Ambiente y Medio Rural y Marino, 2011), consciente de la complejidad de los procesos y en aras de simplificar, aconseja aplicar una condición de contorno de nivel correspondiente al mismo periodo de retorno que el de la avenida que se esté modelizando. Esta forma de proceder no tiene en cuenta la probabilidad de ocurrencia de varios eventos extremos al mismo tiempo.
En este artículo se propone una metodología híbrida de simulación continua que combina la generación de series sintéticas a largo plazo de las variables implicadas, un modelado hidrodinámico bidimensional de alta resolución espacial de la zona de estudio, y técnicas estadísticas de muestreo de datos e interpolación de resultados. La metodología propuesta se ha aplicado a la ciudad costera de Betanzos (noroeste de España), localizada en la confluencia de dos ríos y en la cola de un estuario. Históricamente Betanzos ha tenido problemas de inundación por lo que está catalogada como un Área de Riesgo Potencial Significativo de Inundación (ARPSI) fluvial y costera. Los resultados se han comparado con los obtenidos aplicando la propuesta de la Guía Metodológica para el Desarrollo del Sistema Nacional de Cartografía de Zonas Inundables (Ministerio de Medio Ambiente y Medio Rural y Marino, 2011), observándose que estos últimos sobreestiman de forma considerable los niveles de inundación asociados a un determinado período de retorno.
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A modelling chain was implemented in order to propose a realistic appraisal of the risk in coastal areas affected as well by overflowing as overtopping processes. Simulations are performed through a nested downscaling strategy from regional to local scale at high spatial resolution with explicit buildings, urban structures such as sea front walls and hydraulic structures liable to affect the propagation of water in urban areas. Validation of the model performance is based on hard and soft available data analysis and conversion of qualitative to quantitative information to reconstruct the area affected by flooding and the succession of events during two recent storms. Two joint probability statistical approaches (joint exceedance probability and environmental contour) are used to define 100 years off-shore conditions scenarios and to investigate the flood response to each scenario in term of: (1) maximum spatial extent of flooded areas, (2) volumes of water propagation inland and (3) water level in flooded areas. Scenarios of sea level rise are also considerate in order to evaluate the potential hazard evolution. Our simulations show that for a maximising 100-year hazard scenario, for the municipality as a whole, 38 % of the zones are prone to overflow flooding and 62 % to flooding by propagation of overtopping water volume along the seafront. Results also reveal that for the two kind of statistic scenarios a difference of about 5 % in the forcing conditions (water level, wave height and period) can produce significant differences responses in terms of flooding like +13.5 % of water volumes propagating inland or +11.3 % of affected surfaces. In some areas, flood response appears to be very sensible to the scenario chosen with differences of 0.3 to 0.5 m in water level. The approach developed enable to bracket the 100-year hazard and to characterise spatially the robustness or the uncertainty over the results. Considering a 100-year scenario with mean sea level rise (0.6 m), hazard characteristics are dramatically changed with an evolution of the overtopping/overflowing process ratio and an increase of 384 % in volumes of water propagating inland and 247 % in flooded surfaces.
Two sets of 62-year (1948-2009) and 21-year (1989-2009) high-resolution hindcasts of the meteorological sea level component have been developed for Southern Europe using the Regional Ocean Model System (ROMS) of Rutgers University. These new databases, named GOS 1.1 and GOS 2.1, are a valuable tool for a wide variety of studies, such as those related to a better understanding of sea level variability, flooding risk and coastal engineering studies. The model domain encloses Southern Europe, including the Mediterranean Sea and the Atlantic coast, with a horizontal resolution of 1/8° (~14 km). In order to study the effect of the atmospheric forcing resolution, ROMS is driven with two different regional atmospheric forcings: SeaWind I (30 km of horizontal resolution) and SeaWind II (15 km of horizontal resolution). Both are the result of a dynamical downscaling from global atmospheric reanalysis: NCEP global reanalysis and ERA-Interim global reanalysis, respectively. As a result, two surge data sets are obtained: GOS 1.1 (forced with SeaWind I) and GOS 2.1 (forced with SeaWind II). Surge elevations calculated by ROMS are compared with in situ measurements from tide gauges in coastal areas and with open ocean satellite observations. The validation procedure, testing outcomes from GOS 1.1 and GOS 2.1 against observations, shows the capability of the model to simulate accurately the sea level variation induced by the meteorological forcing. A description of the surge in terms of seasonality and long term trends is also made. The climate variability analysis reveals clear seasonal patterns in the Mediterranean Sea basins. A long-term negative trend for the period 1948-2009 is found, whilst positive trends are computed for the last 20 years (GOS 2.1).
Extreme sea conditions in the nearshore zone are required for coastal flood risk analysis and structural design. Many multivariate extreme value methods that have been applied in the past have been limited by assumptions relating to the dependence structure in the extremes. A conditional extremes statistical model overcomes a number of these previous limitations. To apply the method in practice, a Monte Carlo sampling procedure is required whereby large samples of synthetically generated events are simulated. The use of Monte Carlo approaches, in combination with computationally intensive physical process models, can raise significant practical challenges in terms of computation. To overcome these challenges there has been extensive research into the use of meta-models. Meta-models are approximations of computationally intensive physical process models (simulators). They are derived by fitting functions to the outputs from simulators. Due to their simplified representation they are computationally more efficient than the simulators they approximate.
Here, a methodology for deriving a large Monte Carlo sample of extreme nearshore sea states is described. The methodology comprises the generation of a large sample of offshore sea conditions using the conditional extremes model. A meta-model of the wave transformation process is then constructed. A clustering algorithm is used to aid the development of the meta-model. The large sample of offshore data is then transformed through to the nearshore using the meta-model. The resulting nearshore sea states can be used for the probabilistic design of structures or flood risk analysis. The application of the methodology to a case study site on the North Coast of Spain is described.
Waves in Oceanic and Coastal Waters describes the observation, analysis and prediction of wind-generated waves in the open ocean, in shelf seas, and in coastal regions with islands, channels, tidal flats and inlets, estuaries, fjords and lagoons. The book brings graduate students, researchers and engineers up-to-date with the science and technology involved, assuming only a basic understanding of physics, mathematics and statistics. Most of this richly illustrated book is devoted to the physical aspects of waves. After introducing observation techniques for waves, both at sea and from space, the book defines the parameters that characterize waves. Using basic statistical and physical concepts, the author discusses the prediction of waves in oceanic and coastal waters, first in terms of generalized observations, and then in terms of the more theoretical framework of the spectral energy balance. He gives the results of established theories and also the direction in which research is developing. The book ends with a description of SWAN (Simulating Waves Nearshore), the preferred computer model of the engineering community for predicting waves in coastal waters. Illustrations from the book are featured in color, along with student questions and answers on a web site Includes a detailed description of the wave model SWAN, the preferred computer model of the engineering community for predicting waves in coastal waters Appendices briefly review pre-requisite information on mathematics, statistics and physics
The use of an advanced volume of fluid (VOF)-type model (COBRAS-UC), based on the Reynolds-Averaged Navier-Stokes (RANS) equations, is proposed in this work with the aim of improving the current state of understanding of surf zone processes on natural beaches. Previous studies have suggested that it is important to consider contributions from terms traditionally neglected when assuming a uniform velocity and pressure distribution and a simple turbulence parameterization in surf zone hydrodynamics. In contrast with the Boussinesq and Nonlinear Shallow Water (NSW) equations models, in the RANS models none of the above-mentioned limiting assumptions is required, since no wave theory is imposed and the initiation of wave breaking is predicted by using an advanced turbulence model. Although the model has been widely validated in the laboratory, there is no previous study, to the best of the authors' knowledge, which addresses the applicability of this model to random waves on natural beaches. Free-surface elevation and wave-induced velocity observations, from the SwashX field experiment, are used to validate this model. The model is able to satisfactorily predict the wave evolution and flow characteristics across the surf zone. The model provides a means to obtain high spatial and time resolution information of magnitudes which are difficult or impossible to measure in the field and therefore may contribute to improve our understanding on the physics of surf zone hydrodynamics. Moreover, it is also an excellent tool to obtain useful information of magnitudes involved in different kinds of modeling that require parameterization.
This paper presents the numerical modelling of the cross shore propagation of infragravity waves induced by a transient focuse short wave group over a sloping bottom. A dataset obtained through new laboratory experiments in the wave flume of the Universit of Cantabria is used to validate the Reynolds averaged Navier–Stokes type model IH-2VOF. A new boundary condition based o the wave maker movement used in the experiments is implemented in the model. Shoaling and breaking of short waves as wel as the enhancement of long waves and the energy transfer to low-frequency motion are well addressed by the model, provin the high accuracy in the reproduction of surf zone hydrodynamics. Under the steep slope regime, a long wave trough is radiate offshore from the breakpoint. Numerical simulations conducted for different bottom slopes and short wave steepness sugges that this low-frequency breakpoint generated wave is controlled by both the bed slope parameter and the Iribarren number.
Moreover, the numerical model is used to investigate the influence that a large flat bottom induces on the propagation patter of long waves.
The purpose of this study is to find a combination of optimal numerical algorithms for time-stepping and mode-splitting suitable for a high-resolution, free-surface, terrain-following coordinate oceanic model. Due to mathematical feedback between the baroclinic momentum and tracer equations and, similarly, between the barotropic momentum and continuity equations, it is advantageous to treat both modes so that, after a time step for the momentum equation, the computed velocities participate immediately in the computation of tracers and continuity, and vice versa, rather than advancing all equations for one time step simultaneously. This leads to a new family of time-stepping algorithms that combine forward–backward feedback with the best known synchronous algorithms, allowing an increased time step due to the enhanced internal stability without sacrificing its accuracy. Based on these algorithms we design a split-explicit hydrodynamic kernel for a realistic oceanic model, which addresses multiple numerical issues associated with mode splitting. This kernel utilizes consistent temporal averaging of the barotropic mode via a specially designed filter function to guarantee both exact conservation and constancy preservation properties for tracers and yields more accurate (up to second-order), resolved barotropic processes, while preventing aliasing of unresolved barotropic signals into the slow baroclinic motions. It has a more accurate mode-splitting due to redefined barotropic pressure-gradient terms to account for the local variations in density field, while maintaining the computational efficiency of a split model. It is naturally compatible with a variety of centered and upstream-biased high-order advection algorithms, and helps to mitigate computational cost of expensive physical parameterization of mixing processes and submodels.
A third-generation numerical wave model to compute random, short-crested waves in coastal regions with shallow water and ambient currents (Simulating Waves Nearshore (SWAN)) has been developed, implemented, and validated. The model is based on a Eulerian formulation of the discrete spectral balance of action density that accounts for refractive propagation over arbitrary bathymetry and current fields. It is driven by boundary conditions and local winds. As in other third-generation wave models, the processes of wind generation, whitecapping, quadruplet wave-wave interactions, and bottom dissipation are represented explicitly. In SWAN, triad wave-wave interactions and depth-induced wave breaking are added. In contrast to other third-generation wave models, the numerical propagation scheme is implicit, which implies that the computations are more economic in shallow water. The model results agree well with analytical solutions, laboratory observations, and (generalized) field observations.
When beaches are nourished with a sediment of arbitrary but uniform size, it is found that three types of profiles can result: 1) submerged profiles in which the placed sediment is of smaller diameter than the native and all of the sediment equilibrates underwater with no widening of the dry beach, 2) non-intersecting profiles in which the seaward portion of the placed material lies above the original profile at that location, and 3) intersecting profiles with the placed sand coarser than the native and resulting in the placed profile intersecting with the original profile. -from Author
Runup distributions were measured on a wide spectrum of sandy beaches on the coast of New South Wales, Australia. The data indicate that the Rayleigh distribution is a reasonable statistical model for the maximum level reached by individual waves. The vertical scale of the best-fit distribution is proportional to the wave height times the surf similarity parameter for the steeper beaches in accordance with Hunt's formula for runup of regular waves on structures. For flat beaches, however, the vertical scale of the distribution is independent of the beach slope. The base level for the best-fit distribution (ie the highest level transgressed by all incoming wave crests) is indistinguishable for the sill water level on the steep beaches but significantly lower on flat beaches. The demarcation between 'steep' and 'flat' beaches in these respects is at a beach face slope of approx0.10. The level of the shoreline relative to the runup distribution is a decreasing function of the beach slope. (A)
Coastal flood hazard zones and the design of coastal defenses are often devised using the maximum recorded water level or a ‘design' event such as the 100-year return-level, usually projected from observed extremes. Despite technological advances driving more consistent instrumental records of waves and water levels, the observational record may be short, punctuated with intermittent gaps, and vary in quality. These issues in the record often preclude accurate and robust estimates of extreme return-level events. Here we present a total water level full simulation model (TWL-FSM) that simulates the various components of TWLs (waves, tides, and non-tidal residuals) in a Monte Carlo sense, taking into account conditional dependencies that exist between the various components. Extreme events are modeled using non-stationary extreme value distributions that include seasonality and climate variability. The resulting synthetic TWLs allow for empirical extraction of return level events and the ability to more robustly estimate and assess present-day flood and erosion hazards. The approach is demonstrated along a northern Oregon, USA littoral cell but is applicable to beaches anywhere wave and water level records or hindcasts are available. Simulations result in extreme 100-year TWL return-levels as much as 1 m higher than those extrapolated from the “observational” record. At the Oregon site, this would result in 30% more coastal flooding than the “observational” 100-year TWL return-level projections. More robust estimates of extreme TWLs and tighter confidence bounds on return level events can aid coastal engineers, managers, and emergency planners in evaluating exposure to hazards.
This paper evaluates the energy transfer between short and long waves resulting from nonlinear interactions of the radiation stress with the low-frequency motion in the nearshore. Shoaling and breaking of irregular waves over different slopes are investigated by means of numerical simulations with the Reynolds Averaged Navier–Stokes model IH-2VOF. The low-frequency energy flux is enhanced up to the outer surf zone where dissipation starts. Seaward of the inner surf zone, the rate of work done by the radiation stress roughly balances the low-frequency energy flux gradients, indicating that nonlinear interactions with sea–swell waves are responsible for both the enhancement and the damping of low-frequency energy. In the inner surf zone, interactions between short- and long-wave fields are weak and the low-frequency energy loss appears to be largely due to self–self nonlinear interactions.
Large-scale wave reanalysis databases (0.1°–1° spatial resolution) provide valuable information for wave climate research and ocean applications which require long-term time series (> 20 years) of hourly sea state parameters. However, coastal studies need a more detailed spatial resolution (50–500 m) including wave transformation processes in shallow waters. This specific problem, called downscaling, is usually solved applying a dynamical approach by means of numerical wave propagation models requiring a high computational time effort. Besides, the use of atmospheric reanalysis and wave generation and propagation numerical models introduce some uncertainties and errors that must be dealt with. In this work, we present a global framework to downscale wave reanalysis to coastal areas, taking into account the correction of open sea significant wave height (directional calibration) and drastically reducing the CPU time effort (about 1000 ×) by using a hybrid methodology which combines numerical models (dynamical downscaling) and mathematical tools (statistical downscaling). The spatial wave variability along the boundaries of the propagation domain and the simultaneous wind fields are taking into account in the numerical propagations to performance similarly to the dynamical downscaling approach. The principal component analysis is applied to the model forcings to reduce the data dimension simplifying the selection of a subset of numerical simulations and the definition of the wave transfer function which incorporates the dependency of the wave spatial variability and the non-uniform wind forcings. The methodology has been tested in a case study on the northern coast of Spain and validated using shallow water buoys, confirming a good reproduction of the hourly time series structure and the different statistical parameters.
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.
A third-generation numerical wave model to compute random, short-crested waves in coastal regions with shallow water and ambient currents (Simulating Waves Nearshore (SWAN)) has been developed, implemented, and validated. The model is based on a Eulerian formulation of the discrete spectral balance of action density that accounts for refractive propagation over arbitrary bathymetry and current fields. It is driven by boundary conditions and local winds. As in other third-generation wave models, the processes of wind generation, whitecapping, quadruplet wave-wave interactions, and bottom dissipation are represented explicitly. In SWAN, triad wave-wave interactions and depth-induced wave breaking are added. In contrast to other third-generation wave models, the numerical propagation scheme is implicit, which implies that the computations are more economic in shallow water. The model results agree well with analytical solutions, laboratory observations, and (generalized) field observations.
Long-term time series of sea state parameters are required in different coastal engineering applications. In order to obtain wave data at shallow water and due to the scarcity of instrumental data, ocean wave reanalysis databases ought to be downscaled to increase the spatial resolution and simulate the wave transformation process. In this paper, a hybrid downscaling methodology to transfer wave climate to coastal areas has been developed combining a numerical wave model (dynamical downscaling) with mathematical tools (statistical downscaling). A maximum dissimilarity selection algorithm (MDA) is applied in order to obtain a representative subset of sea states in deep water areas. The reduced number of selected cases spans the marine climate variability, guaranteeing that all possible sea states are represented and capturing even the extreme events. These sea states are propagated using a state-of-the-art wave propagation model. The time series of the propagated sea state parameters at a particular location are reconstructed using a non-linear interpolation technique based on radial basis functions (RBFs), providing excellent results in a high dimensional space with scattered data as occurs in the cases selected with MDA. The numerical validation of the results confirms the ability of the developed methodology to reconstruct sea state time series in shallow water at a particular location and to estimate different spatial wave climate parameters with a considerable reduction in the computational effort.
Many coastal engineering problems require an estimate of the seaward limit of sediment transport, defined as the minimum depth at which no measurable change in water depth occurs. A procedure to estimate this limit depth was evaluated using measurements collected at the Coastal Engineering Research Center's Field Research Facility located on the Atlantic Ocean. The data consisted of measured wave characteristics and accurate repetitive nearshore surveys which extended out to a depth of 30 ft (9 m). Ten unique data points were used in the evaluation with measured limit depths ranging from 18 to 21 (3.9 to 6.4 m). These depths were overpredicted by an average of 4.6 ft (1.4 m). This difference could be reduced to 1.3 ft (0.4 m) by adjusting the coefficients in the equation. A reasonable correlation was also obtained using a simple multiple of wave height.
Statistics of wave run-up maxima have been calculated for 149 35-minutes data runs from a natural beach. During the experiment incident wave height varied from 0.4 to 4.0 m, incident wave period from 6 to 16 s, and beach face slope from 0.07 to 0.20. Four extreme statistics were calculated; the maximum run-up height during each run, the 2% exceedence level of shoreline elevation, the 2% exceedence height for individual run-up peaks, and the 2% exceedence level for swash height as determined by the zero-upcrossing method. These statistics were best parameterized when normalized by the incident significant wave height and plotted against the Iribarren number, . The swash data (with set-up removed) showed less scatter than total run-up (with set-up included). For Iribarren number greater than 1.5 the run-up was dominated by the incident frequencies, for lower Iribarren number longer period motions dominated the swash. A reasonable value of wave steepness for a fully developed storm sea is 0.025 so that a storm Iribarren number can be estimated as 6.3 times the beach slope. Using this and an offshore design wave height, the included graphs may provide guidance in determining a design run-up height.
Recent studies reveal important trends in mean values and high percentiles of significant wave height in the northeast Pacific. However, changes of the extreme wave heights through time have not received much attention. In this work, the long-term variability of extreme significant wave height along the northeast Pacific is modeled using a time-dependent extreme value model. Application of the model to significant wave height data sets from 26 buoys over the period 1985–2007 shows significant positive long-term trends in extreme wave height between 30–45°N near the western coast of the US averaging 2.35 cm/yr. We also demonstrate an impact of El Niño on extreme wave heights (about 25 cm per unit of NINO3.4 index) in the northeast Pacific as well as important correlations with mid-latitudinal climate patterns (e.g., NP and PNA indices).
[1] Recent evidence suggests long-term changes in the intensity and frequency of extreme wave climate around the globe. These changes may be attributable to global warming as well as to the natural climate variability. A statistical model to estimate long-term trends in the frequency and intensity of severe storm waves is presented in this paper. The model is based on a time-dependent version of the Peak Over Threshold model and is applied to the Washington NOAA buoy (46005) significant wave height data set. The model allows consideration of the annual cycle, trends, and relationship to atmosphere- ocean-related indices. For the particular data set analyzed the inclusion of seasonal variability substantially improves the correlation between the model and the data. Also, significant correlations with the Pacific–North America pattern, as well as long-term trend, are detected. Results show that the model is appropriate for a rigorous analysis of long-term trends and variability of extreme waves and for providing time-dependent quantiles and confidence intervals.
Coastal areas are vital economic hubs in terms of settlement, industry, agriculture, trade and tourism to mention some key sectors. There are already many coastal problems including erosion, flood risk and long-term habitat deterioration. As economies continue to develop the asset base at risk will grow, while accelerating climate change will increase the likelihood of damaging extreme events, as well as accelerate habitat decline. Existing coastal management and defence approaches are not well tuned to these challenges as they assume a static situation.THESEUS project is developing a systematic approach to delivering both a low-risk coast for human use and healthy habitats for evolving coastal zones subject to multiple change factors. The project examines innovative mitigation and adaptation technologies and integrate the best of these technical measures in a strategic policy context through overarching guidelines. THESEUS activities are carried out within a multidisciplinary framework using 8 study sites across Europe, with specific attention to the most vulnerable coastal environments such as deltas, estuaries and wetlands, where many large cities and industrial areas are located.This paper describes THESEUS approach, and specifically: the Source-Pathway-Receptor-Consquence model for coastal risk assessment; the engineering, social, economic and ecological mitigation measures under analysis; the participatory approach with end users and coastal authorities for the selection and identification of the appropriate defence strategy to be planned in sudy sites.
Recent wave reanalysis databases require the application of techniques capable of managing huge amounts of information. In this paper, several clustering and selection algorithms: K-Means (KMA), self-organizing maps (SOM) and Maximum Dissimilarity (MDA) have been applied to analyze trivariate hourly time series of met-ocean parameters (significant wave height, mean period, and mean wave direction). A methodology has been developed to apply the aforementioned techniques to wave climate analysis, which implies data pre-processing and slight modifications in the algorithms. Results show that: a) the SOM classifies the wave climate in the relevant “wave types” projected in a bidimensional lattice, providing an easy visualization and probabilistic multidimensional analysis; b) the KMA technique correctly represents the average wave climate and can be used in several coastal applications such as longshore drift or harbor agitation; c) the MDA algorithm allows selecting a representative subset of the wave climate diversity quite suitable to be implemented in a nearshore propagation methodology.
This work aims to demonstrate an advancement towards the integrated modelling of surf zone hydrodynamics by means of a VOF-type numerical model (COBRAS-UC) based on the Reynolds-Averaged Navier–Stokes equations. In this paper, the numerical model is adapted and validated for the study of nearshore processes on a mildly-sloping beach. The model prediction of wave energy transformation and higher order statistics (skewness and asymmetry) are in good agreement with detailed laboratory observations from a barred beach [Boers, M. (1996). “Simulation of a surf zone with a barred beach; Report 1: Wave heights and wave breaking”. Tech. Rep.96-5, Comm. on Hydrol. and Geol. Eng., Dept. of Civil Engineering, Delft University of Technology]. Moreover, the numerical model allows us to study the low-frequency motions inside the surf zone. It is found that in order to achieve a satisfactory simulation of both short- and long-wave transformation, the numerical model must achieve: (i) the simultaneous second-order wave generation and absorption, (ii) the energy transfer between triad of components, (iii) the short- and long-wave energy dissipation inside the surf zone, and (iv) the wave reflection at the shoreline. Comparisons between numerical and experimental results demonstrate the model capability to satisfactorily simulate all the aforementioned processes.
A user-friendly system called coastal modeling system (SMC) has been developed by the Spanish Ministry of Environment and the University of Cantabria. The system includes several numerical models specifically developed for the application of the methodology proposed in the Spanish Beach Nourishment and Protection Manual. According to this methodology, the SMC is structured into five-modules: (1) Pre-process module; (2) Short-term module; (3) Long-term module; (4) Coastal terrain module; and (5) Tutorial module. The pre-process module allows the processing of a database of morphodynamic information used as input for the different programs and models of the SMC. Short-, Long-term modules include numerical models to analyze coastal systems on different scales of variability (hours–months–years) and are composed of morphodynamic evolution models in cross-profile 2DV and beach plan 2DH. The coastal terrain module allows the user to modify the working bathymetry and to combine bathymetries from different sources in only one working bathymetry. The tutorial module includes a comprehensive collection of coastal engineering design and analysis software. The SMC has a dynamic design and allows the incorporation of future new databases and morphodynamic models. The SMC system is freely distributed to coastal practitioners and has already been implemented in several countries.
Using shoreline water-level time series collected during 10 dynamically diverse field experiments, an empirical parameterization for extreme runup, defined by the 2% exceedence value, has been developed for use on natural beaches over a wide range of conditions. Runup, the height of discrete water-level maxima, depends on two dynamically different processes; time-averaged wave setup and total swash excursion, each of which is parameterized separately. Setup at the shoreline was best parameterized using a dimensional form of the more common Iribarren-based setup expression that includes foreshore beach slope, offshore wave height, and deep-water wavelength. Significant swash can be decomposed into the incident and infragravity frequency bands. Incident swash is also best parameterized using a dimensional form of the Iribarren-based expression. Infragravity swash is best modeled dimensionally using offshore wave height and wavelength and shows no statistically significant linear dependence on either foreshore or surf-zone slope. On infragravity-dominated dissipative beaches, the magnitudes of both setup and swash, modeling both incident and infragravity frequency components together, are dependent only on offshore wave height and wavelength. Statistics of predicted runup averaged over all sites indicate a − 17 cm bias and an rms error of 38 cm: the mean observed runup elevation for all experiments was 144 cm. On intermediate and reflective beaches with complex foreshore topography, the use of an alongshore-averaged beach slope in practical applications of the runup parameterization may result in a relative runup error equal to 51% of the fractional variability between the measured and the averaged slope.
As the most costly US natural disaster in history, Hurricane Katrina fostered the IPET forensic study to better understand the event. All available observations from several hundred space-, land-, sea-, and aircraft-based measurement platforms were gathered and processed to a common framework for height, exposure, and averaging time, to produce a series of wind field snapshots at 3 h intervals to depict the wind structure of Katrina when in the Gulf of Mexico. The stepped-frequency microwave radiometer was calibrated against GPS sondes to establish the upper range of the instrument and then used to determine the wind field in the storm's core region in concert with airborne Doppler radar winds adjusted to the surface from near the top of the PBL (500 m). The SFMR data were used to develop a method to estimate surface winds from 3 km level reconnaissance aircraft observations, taking into consideration the observed azimuthal variation of the reduction factor. The “SFMR method” was used to adjust reconnaissance flight-level measurements to the surface in the core region when SFMR and Doppler winds were not available. A variety of coastal and inland mesonet data were employed, including portable towers deployed by Texas Tech University, University of Louisiana at Monroe, and the Florida Coastal Monitoring Program, as well as fixed mesonet stations from Louisiana State Universities Marine Consortium, University of Southern Mississippi, and Agricultural Networks from Louisiana, Mississippi, and Alabama, and the Coastal Estuarine Network of Alabama and Mississippi. Also included were land- (WSR-88D VAD and GBVTD, ASOS, Metar, LLWAS, HANDAR), space- (QuikScat, GOES cloud drift winds, WindSat), and marine- (GPS sondes, Buoys, C-MAN, ships) platforms. The wind fields serve as an analysis of record and were used to provide forcing for wave and storm surge models to produce hindcasts of water levels in the vicinity of flood control structures.
A description of the Eastern North Atlantic tidal dynamics (in a region spanning from 20°N to 48°N in latitude and from 34°W to 0° in longitude) is obtained by means of new in situ measurements and numerical modelling based on TOPEX/POSEIDON-derived data sets.The main source of measurements is the tide gauge network REDMAR (RED de MAReógrafos de Puertos del Estado), operative since July 1992 and managed by Clima Marítimo (Puertos del Estado). Results derived from the harmonic analysis of the first years of measurements are presented and compared with model results. In order to obtain a global picture of the tides in the region, a large compilation of harmonic constants obtained from other institutes is included.The availability of new TOPEX/POSEIDON-derived harmonic constants data sets provides a chance to include the benefits derived from satellite altimetry in high resolution regional applications of numerical models. Richard Ray's tidal model (Ray et al., 1994), based on a response type tidal analysis of TOPEX/POSEIDON data, was employed within a model of the studied area. The numerical model employed is HAMSOM, a 3-D finite difference code developed both by the Institut für Meereskunde (Hamburg University) and Clima Marítimo. Results from simulations of seven major harmonics are presented, providing a comprehensive view of tidal dynamics, including current information.The results of tidal simulations show good agreement between semidiurnal harmonic components and the values measured by both coastal and pelagic tidal gauges and by current meters. The modelled diurnal constituents show larger relative differences with measurements than semidiurnal harmonics, especially concerning the phase lags.The non-linear transfer of energy from semidiurnal to higher order harmonics, such as M4 and M6, was mapped. Those transfers were found to be important only in two areas: the French continental shelf in the Bay of Biscay and the widest part of the African shelf, south of Cabo Bojador.
A standard part of any oceanic pressure gauge or current meter analysis is the separation of tidal from non-tidal components of the signal. The tidal signal can either be discarded, or its characteristics described in some fashion useful for further analysis. Although tidal signals can be removed by standard high or bandpass filtering techniques, their relatively deterministic character and large amplitude make special techniques more effective. In classical harmonic analysis, the tidal signal is modelled as the sum of a finite set of sinusoids at specific frequencies related to astronomical parameters. A set of programs has been written in MATLAB to (a) perform classical harmonic analysis for periods of about 1 year or shorter, (b) account for (some) unresolved constituents using nodal corrections, and (c) compute confidence intervals for the analyzed components.
The unstructured-mesh SWAN spectral wave model and the ADCIRC shallow-water circulation model have been integrated into a tightly-coupled SWAN + ADCIRC model. The model components are applied to an identical, unstructured mesh; share parallel computing infrastructure; and run sequentially in time. Wind speeds, water levels, currents and radiation stress gradients are vertex-based, and therefore can be passed through memory or cache to each model component. Parallel simulations based on domain decomposition utilize identical sub-meshes, and the communication is highly localized. Inter-model communication is intra-core, while intra-model communication is inter-core but is local and efficient because it is solely on adjacent sub-mesh edges. The resulting integrated SWAN + ADCIRC system is highly scalable and allows for localized increases in resolution without the complexity or cost of nested meshes or global interpolation between heterogeneous meshes. Hurricane waves and storm surge are validated for Hurricanes Katrina and Rita, demonstrating the importance of inclusion of the wave-circulation interactions, and efficient performance is demonstrated to 3062 computational cores.
Wave Overtopping of Sea Defences and Related Structures - Assessment Manual
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Centro Nacional de Información Geográfica / Instituto Geográfico Nacional(Spanish Geographic Institute) Madrid (Spain) In Spanish
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- Holthuijsen