Pub Date : 2024-11-02DOI: 10.1016/j.coastaleng.2024.104631
Tyler McCormack , Julia Hopkins , Britt Raubenheimer , Steve Elgar , Katherine L. Brodie
Wave-orbital velocities are estimated with particle image velocimetry (PIV) applied to rapid sequences of images of the surfzone surface obtained with a low-cost camera mounted on an amphibious tripod. Time series and spectra of the remotely sensed cross-shore wave-orbital velocities are converted to the depth of colocated acoustic Doppler velocimeters (ADVs), using linear finite depth theory. These converted velocities are similar to the velocities measured in situ (mean nRMSE for time series = 16% and for spectra = 10%). Small discrepancies between depth-attenuated surface and in situ currents may be owing to errors in the surface velocity measurements, uncertainties in the water depth, the vertical elevation of the ADVs, and the neglect of nonlinear effects when using linear finite depth theory. These results show the potential to obtain spatially dense estimates of wave velocities using optical near-field remote methods during field campaigns and continuous monitoring operations.
{"title":"Remote sensing of wave-orbital velocities in the surfzone","authors":"Tyler McCormack , Julia Hopkins , Britt Raubenheimer , Steve Elgar , Katherine L. Brodie","doi":"10.1016/j.coastaleng.2024.104631","DOIUrl":"10.1016/j.coastaleng.2024.104631","url":null,"abstract":"<div><div>Wave-orbital velocities are estimated with particle image velocimetry (PIV) applied to rapid sequences of images of the surfzone surface obtained with a low-cost camera mounted on an amphibious tripod. Time series and spectra of the remotely sensed cross-shore wave-orbital velocities are converted to the depth of colocated acoustic Doppler velocimeters (ADVs), using linear finite depth theory. These converted velocities are similar to the velocities measured in situ (mean nRMSE for time series = 16% and for spectra = 10%). Small discrepancies between depth-attenuated surface and in situ currents may be owing to errors in the surface velocity measurements, uncertainties in the water depth, the vertical elevation of the ADVs, and the neglect of nonlinear effects when using linear finite depth theory. These results show the potential to obtain spatially dense estimates of wave velocities using optical near-field remote methods during field campaigns and continuous monitoring operations.</div></div>","PeriodicalId":50996,"journal":{"name":"Coastal Engineering","volume":"195 ","pages":"Article 104631"},"PeriodicalIF":4.2,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-29DOI: 10.1016/j.coastaleng.2024.104641
Michael Itzkin, Margaret L. Palmsten, Mark L. Buckley, Justin J. Birchler, Legna M. Torres-Garcia
The coastal zone is a dynamic region that can change rapidly and significantly with respect to the morphology of the beach and incoming wave conditions. Runup forecasts may be improved by adapting a dynamic approach that allows for different runup models to be implemented in response to changes in beach state. Accurately forecasting wave runup is critical to characterize exposure to coastal hazards and provide an early warning against potential erosion and inundation. Here, we developed a decision tree model to produce a weighted ensemble of existing runup models to predict 1.25 years of runup at Duck, North Carolina, USA. We then applied the calibrated decision tree model to reproduce observed runup during the DUNEX experiment in Pea Island, North Carolina, USA. We found that the decision tree approach yielded a prediction that was comparable or greater in accuracy (i.e. higher r2, lower RMSE) than the individual runup models. We also interrogated the decision tree predictions to determine how the individual models perform relative to each other and why certain models perform better than others under the same observed wave and beach conditions. We found that the decision tree approach drew on the processes represented in the individual models in the ensemble to produce a forecast that is accurate and explainable without relying on prior knowledge of the study site(s) or requiring manual adjustments beyond the initial model training.
{"title":"Developing a decision tree model to forecast runup and assess uncertainty in empirical formulations","authors":"Michael Itzkin, Margaret L. Palmsten, Mark L. Buckley, Justin J. Birchler, Legna M. Torres-Garcia","doi":"10.1016/j.coastaleng.2024.104641","DOIUrl":"10.1016/j.coastaleng.2024.104641","url":null,"abstract":"<div><div>The coastal zone is a dynamic region that can change rapidly and significantly with respect to the morphology of the beach and incoming wave conditions. Runup forecasts may be improved by adapting a dynamic approach that allows for different runup models to be implemented in response to changes in beach state. Accurately forecasting wave runup is critical to characterize exposure to coastal hazards and provide an early warning against potential erosion and inundation. Here, we developed a decision tree model to produce a weighted ensemble of existing runup models to predict 1.25 years of runup at Duck, North Carolina, USA. We then applied the calibrated decision tree model to reproduce observed runup during the DUNEX experiment in Pea Island, North Carolina, USA. We found that the decision tree approach yielded a prediction that was comparable or greater in accuracy (i.e. higher r<sup>2</sup>, lower RMSE) than the individual runup models. We also interrogated the decision tree predictions to determine how the individual models perform relative to each other and why certain models perform better than others under the same observed wave and beach conditions. We found that the decision tree approach drew on the processes represented in the individual models in the ensemble to produce a forecast that is accurate and explainable without relying on prior knowledge of the study site(s) or requiring manual adjustments beyond the initial model training.</div></div>","PeriodicalId":50996,"journal":{"name":"Coastal Engineering","volume":"195 ","pages":"Article 104641"},"PeriodicalIF":4.2,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142573346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-29DOI: 10.1016/j.coastaleng.2024.104645
Guillaume Coulaud , Maria Teles , Michel Benoit
Weakly dispersive Boussinesq-type models are extensively used to model long-wave propagation in coastal areas and their interaction with coastal infrastructures. Many equations falling in this category have been formulated during the last decades, but few detailed comparisons between them can be found in the literature. In this work, we investigate theoretically and with computational experiments eight variants of the most popular models used by the coastal engineering community. Both weakly nonlinear and fully nonlinear models are considered, hoping to understand better when the additional complexity of the latter class of models is necessary or justified. We provide an overview and discuss the properties of these models, including the linear dispersion relation in uniform water depth, the second-order nonlinear coupling coefficient, the shoaling gradient, and the sensitivity to wave trough instabilities. The models are then numerically discretised using the same general strategy in a single numerical code, using fourth-order methods for time and space discretisation. Their capacity to simulate coastal wave propagation and their transformation when approaching the shore is assessed on three challenging one-dimensional benchmarks. It appears that fully nonlinear models are more consistent than their weakly nonlinear counterparts, which can occasionally perform better but show different behaviours depending on the case.
{"title":"A comparison of eight weakly dispersive Boussinesq-type models for non-breaking long-wave propagation in variable water depth","authors":"Guillaume Coulaud , Maria Teles , Michel Benoit","doi":"10.1016/j.coastaleng.2024.104645","DOIUrl":"10.1016/j.coastaleng.2024.104645","url":null,"abstract":"<div><div>Weakly dispersive Boussinesq-type models are extensively used to model long-wave propagation in coastal areas and their interaction with coastal infrastructures. Many equations falling in this category have been formulated during the last decades, but few detailed comparisons between them can be found in the literature. In this work, we investigate theoretically and with computational experiments eight variants of the most popular models used by the coastal engineering community. Both weakly nonlinear and fully nonlinear models are considered, hoping to understand better when the additional complexity of the latter class of models is necessary or justified. We provide an overview and discuss the properties of these models, including the linear dispersion relation in uniform water depth, the second-order nonlinear coupling coefficient, the shoaling gradient, and the sensitivity to wave trough instabilities. The models are then numerically discretised using the same general strategy in a single numerical code, using fourth-order methods for time and space discretisation. Their capacity to simulate coastal wave propagation and their transformation when approaching the shore is assessed on three challenging one-dimensional benchmarks. It appears that fully nonlinear models are more consistent than their weakly nonlinear counterparts, which can occasionally perform better but show different behaviours depending on the case.</div></div>","PeriodicalId":50996,"journal":{"name":"Coastal Engineering","volume":"195 ","pages":"Article 104645"},"PeriodicalIF":4.2,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142573348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pile groups are extensively utilized as supports for many coastal structures, such as bridges, jetties, and oil production platforms. The problem of understanding the interaction effects within pile groups and predicting the breaking wave forces on them is considered in this paper, using experimental tests and machine learning-based predictive modeling. The restriction of previous studies on this important engineering problem is that the pile group arrangements considered are limited. Prediction methods are therefore developed only for specific pile group arrangements and do not incorporate the effect of the incident wave direction. In this study, to partially overcome this limitation, an extensive experimental investigation is conducted on 70 different pile group arrangements under six breaking wave conditions. Three pile group coefficients, characterized by the total, quasi-static, and dynamic forces, are introduced for a thorough assessment of the interaction effects within the pile group. First, the pile group coefficients for three basic arrangements (tandem, side-by-side, and staggered) are evaluated. The results reveal a sheltering effect in the tandem arrangement and an amplification effect in the side-by-side arrangement. However, the forces on the measured pile in the staggered arrangement resemble those on the isolated pile, with neither significant sheltering nor amplification effects observed. Then, the results for all arrangements highlight the significant effect of wave direction on the pile group coefficients for small inter-pile spacing. Finally, different machine learning algorithms are adopted to develop predictive models for the group coefficients. The XGBoost model demonstrates superior accuracy for predicting the total and quasi-static force coefficients, while the dynamic force coefficient remains challenging to predict accurately due to its stochastic nature.
{"title":"Group interaction effect on breaking wave forces on a vertical pile: Experimental tests and predictive models","authors":"Xiutao Jiang , Zegao Yin , Yanxu Wang , Rengong Zhang","doi":"10.1016/j.coastaleng.2024.104651","DOIUrl":"10.1016/j.coastaleng.2024.104651","url":null,"abstract":"<div><div>Pile groups are extensively utilized as supports for many coastal structures, such as bridges, jetties, and oil production platforms. The problem of understanding the interaction effects within pile groups and predicting the breaking wave forces on them is considered in this paper, using experimental tests and machine learning-based predictive modeling. The restriction of previous studies on this important engineering problem is that the pile group arrangements considered are limited. Prediction methods are therefore developed only for specific pile group arrangements and do not incorporate the effect of the incident wave direction. In this study, to partially overcome this limitation, an extensive experimental investigation is conducted on 70 different pile group arrangements under six breaking wave conditions. Three pile group coefficients, characterized by the total, quasi-static, and dynamic forces, are introduced for a thorough assessment of the interaction effects within the pile group. First, the pile group coefficients for three basic arrangements (tandem, side-by-side, and staggered) are evaluated. The results reveal a sheltering effect in the tandem arrangement and an amplification effect in the side-by-side arrangement. However, the forces on the measured pile in the staggered arrangement resemble those on the isolated pile, with neither significant sheltering nor amplification effects observed. Then, the results for all arrangements highlight the significant effect of wave direction on the pile group coefficients for small inter-pile spacing. Finally, different machine learning algorithms are adopted to develop predictive models for the group coefficients. The XGBoost model demonstrates superior accuracy for predicting the total and quasi-static force coefficients, while the dynamic force coefficient remains challenging to predict accurately due to its stochastic nature.</div></div>","PeriodicalId":50996,"journal":{"name":"Coastal Engineering","volume":"195 ","pages":"Article 104651"},"PeriodicalIF":4.2,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The atmosphere-wave interaction is an important physical process during tropical cyclones. Understanding and modelling of this process are of great significance for the technical and functional design of coastal and harbor structures. At the high wind velocities of tropical cyclones, foams and sprays that are blown away from the sea form a slip layer between the atmosphere and the sea surface. This slip layer makes the atmosphere-wave interaction exhibit different characteristics compared with that at low wind velocities. The significant effect of this layer on the atmosphere is the reduction of aero-dynamical surface roughness, which has been used to improve the expression of the drag coefficient. On this basis, the effect of the slip layer on the sea surface is further explored in this study. The whitecap coverage may reach a low limit at high wind velocities, and a modified numerical method of whitcapping dissipation for the wave spectrum model is proposed based on the classic field observations of whitecaps. According to these observations, when developing waves appear, the variation characteristics of whitecap coverage are different from those of developed waves with low wind velocities. Thus, the critical friction velocity of wave states should be defined, which can be expressed by the threshold steepness of developed waves due to the negative correlation between wave age and wave steepness. The dissipation mode is then modified to gradually reach the limit with the increase of friction velocities, which is validated during 24 tropical cyclones measured with 26 buoys. The negative Bias of the default mode generally decreases with the increase of friction velocity, even reaching −0.8 m, while the Bias of the modified mode is mostly maintained between 0.2 m and −0.2 m.
{"title":"Study on whitecapping dissipation process for wave modelling during tropical cyclones","authors":"Wenxuan Sun , Zhuxiao Shao , Bingchen Liang , Huijun Gao","doi":"10.1016/j.coastaleng.2024.104650","DOIUrl":"10.1016/j.coastaleng.2024.104650","url":null,"abstract":"<div><div>The atmosphere-wave interaction is an important physical process during tropical cyclones. Understanding and modelling of this process are of great significance for the technical and functional design of coastal and harbor structures. At the high wind velocities of tropical cyclones, foams and sprays that are blown away from the sea form a slip layer between the atmosphere and the sea surface. This slip layer makes the atmosphere-wave interaction exhibit different characteristics compared with that at low wind velocities. The significant effect of this layer on the atmosphere is the reduction of aero-dynamical surface roughness, which has been used to improve the expression of the drag coefficient. On this basis, the effect of the slip layer on the sea surface is further explored in this study. The whitecap coverage may reach a low limit at high wind velocities, and a modified numerical method of whitcapping dissipation for the wave spectrum model is proposed based on the classic field observations of whitecaps. According to these observations, when developing waves appear, the variation characteristics of whitecap coverage are different from those of developed waves with low wind velocities. Thus, the critical friction velocity of wave states should be defined, which can be expressed by the threshold steepness of developed waves due to the negative correlation between wave age and wave steepness. The dissipation mode is then modified to gradually reach the limit with the increase of friction velocities, which is validated during 24 tropical cyclones measured with 26 buoys. The negative Bias of the default mode generally decreases with the increase of friction velocity, even reaching −0.8 m, while the Bias of the modified mode is mostly maintained between 0.2 m and −0.2 m.</div></div>","PeriodicalId":50996,"journal":{"name":"Coastal Engineering","volume":"195 ","pages":"Article 104650"},"PeriodicalIF":4.2,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142552562","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An analytical framework is presented to describe the attenuation of regular and irregular waves propagating over floating seaweed farms. Kelp blades suspended on longlines are modelled, as a first approximation, as rigid bars rotating around their upper ends. Assuming small-amplitude blade motions under low to moderate sea conditions, the frequency-dependent transfer function of the rotations can be obtained, with quadratic drag loads linearized. Subsequently, the hydrodynamic problem with regular waves propagating over suspended seaweed canopies is formulated using the continuity equation and linearized momentum equations with additional source terms in the vegetation region. Analytical solutions are obtained for attenuated regular waves with their heights decaying exponentially as they propagate over the canopy. These solutions are utilized as the basis for predicting wave attenuation of irregular waves while stochastic linearization of the quadratic drag loads is employed. In contrast to energy-conservation-based models, which assume the velocity profile follows linear wave theory, the present solution can predict the reduced velocity inside the canopy. The analytical solutions are validated against experimental data and verified against a numerical flow solver. The model is capable of resolving the wave attenuation, along with velocity profiles and phase lag. Drag and inertial force exhibit cancellation effects on wave decay and both affect phase lag.
{"title":"Wave attenuation by cultivated seaweeds: A linearized analytical model","authors":"Zhilong Wei , Morgane Weiss , Trygve Kristiansen , David Kristiansen , Yanlin Shao","doi":"10.1016/j.coastaleng.2024.104642","DOIUrl":"10.1016/j.coastaleng.2024.104642","url":null,"abstract":"<div><div>An analytical framework is presented to describe the attenuation of regular and irregular waves propagating over floating seaweed farms. Kelp blades suspended on longlines are modelled, as a first approximation, as rigid bars rotating around their upper ends. Assuming small-amplitude blade motions under low to moderate sea conditions, the frequency-dependent transfer function of the rotations can be obtained, with quadratic drag loads linearized. Subsequently, the hydrodynamic problem with regular waves propagating over suspended seaweed canopies is formulated using the continuity equation and linearized momentum equations with additional source terms in the vegetation region. Analytical solutions are obtained for attenuated regular waves with their heights decaying exponentially as they propagate over the canopy. These solutions are utilized as the basis for predicting wave attenuation of irregular waves while stochastic linearization of the quadratic drag loads is employed. In contrast to energy-conservation-based models, which assume the velocity profile follows linear wave theory, the present solution can predict the reduced velocity inside the canopy. The analytical solutions are validated against experimental data and verified against a numerical flow solver. The model is capable of resolving the wave attenuation, along with velocity profiles and phase lag. Drag and inertial force exhibit cancellation effects on wave decay and both affect phase lag.</div></div>","PeriodicalId":50996,"journal":{"name":"Coastal Engineering","volume":"195 ","pages":"Article 104642"},"PeriodicalIF":4.2,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142573345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-26DOI: 10.1016/j.coastaleng.2024.104646
Thomas A.G. Smyth , Thomas Pagon , Ian J. Walker
Coastal dunes offer a wide range of valuable ecosystem services such as protection from erosion, flooding, sea-level rise, and provision of specialised habitat for endangered, endemic, or migratory species. Foredune blowouts and landward migrating parabolic dunes play an important role in many coastal dune settings creating ecological heterogeneity associated with inland sand transport, nutrient supply, and geomorphic disturbance processes. However, as coastal dunes globally are being increasingly stabilised by vegetation and declining in their ecological resilience and functionality, anthropogenic interventions, such as the removal of invasive species and excavation of foredune notches, have emerged to simulate and restore critical aeolian processes required to maintain dune morphodynamics and onshore sediment transport between the beach and inland dunes. This study employed computational fluid dynamics (CFD) modelling to investigate key controls on the wind flow dynamics and sand transport potential within idealised foredune notches of varying widths, slopes, and planform shape (rectangular vs. trapezoidal) for perpendicular and oblique incident wind directions. Compared with empirical findings from similarly engineered notches, our results show that notch width significantly influences shear velocity in the excavated notch ‘slot’, with narrower notches (25 m wide) enhancing wind flow acceleration and inland sediment transport potential. Spatial patterns of shear velocity throughout notches were also sensitive to incident wind direction, with maximum shear velocities, and consequent inland sand transport potential, occurring when winds were parallel to the orientation of the notch. On the lobes of the notches, shear velocity and sand transport potential were greatest during oblique winds. Our results suggest that a relatively narrow notch (e.g. 25 m as opposed to 50 m or 100 m), aligned with the prevailing wind direction, creates the most favourable conditions for transporting sediment from the beach to the dune behind. These findings underscore the importance of notch design in coastal dune restoration, offering critical insights for optimising interventions aimed at sustaining aeolian sediment transport from the beach to the hinterdune.
{"title":"Exploring wind flow dynamics in foredune notches using Computational Fluid Dynamics (CFD)","authors":"Thomas A.G. Smyth , Thomas Pagon , Ian J. Walker","doi":"10.1016/j.coastaleng.2024.104646","DOIUrl":"10.1016/j.coastaleng.2024.104646","url":null,"abstract":"<div><div>Coastal dunes offer a wide range of valuable ecosystem services such as protection from erosion, flooding, sea-level rise, and provision of specialised habitat for endangered, endemic, or migratory species. Foredune blowouts and landward migrating parabolic dunes play an important role in many coastal dune settings creating ecological heterogeneity associated with inland sand transport, nutrient supply, and geomorphic disturbance processes. However, as coastal dunes globally are being increasingly stabilised by vegetation and declining in their ecological resilience and functionality, anthropogenic interventions, such as the removal of invasive species and excavation of foredune notches, have emerged to simulate and restore critical aeolian processes required to maintain dune morphodynamics and onshore sediment transport between the beach and inland dunes. This study employed computational fluid dynamics (CFD) modelling to investigate key controls on the wind flow dynamics and sand transport potential within idealised foredune notches of varying widths, slopes, and planform shape (rectangular vs. trapezoidal) for perpendicular and oblique incident wind directions. Compared with empirical findings from similarly engineered notches, our results show that notch width significantly influences shear velocity in the excavated notch ‘slot’, with narrower notches (25 m wide) enhancing wind flow acceleration and inland sediment transport potential. Spatial patterns of shear velocity throughout notches were also sensitive to incident wind direction, with maximum shear velocities, and consequent inland sand transport potential, occurring when winds were parallel to the orientation of the notch. On the lobes of the notches, shear velocity and sand transport potential were greatest during oblique winds. Our results suggest that a relatively narrow notch (e.g. 25 m as opposed to 50 m or 100 m), aligned with the prevailing wind direction, creates the most favourable conditions for transporting sediment from the beach to the dune behind. These findings underscore the importance of notch design in coastal dune restoration, offering critical insights for optimising interventions aimed at sustaining aeolian sediment transport from the beach to the hinterdune.</div></div>","PeriodicalId":50996,"journal":{"name":"Coastal Engineering","volume":"195 ","pages":"Article 104646"},"PeriodicalIF":4.2,"publicationDate":"2024-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142552561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-25DOI: 10.1016/j.coastaleng.2024.104648
Filipe Miranda , Diogo Mendes , José Miguel Castro , Paulo Rosa-Santos , Francisco Taveira-Pinto , Tiago Fazeres-Ferradosa
A physical modelling study was carried out to investigate random wave damping promoted by an idealized floating kelp farm. The experimental conditions spanned intermediate water depths and both linear and nonlinear water waves. Unlike previous studies of wave damping promoted by vegetation, the floating kelp farm was placed close to the water surface with a ratio between vegetation height and water depth close to 0.25. The wave transmission coefficient induced by the floating kelp farm ranged between 0.56 and 0.96. This coefficient decreased for longer floating kelp farms and it was a function of the ratio between kelp farm length and incident wavelength and of the relative wave depth. Spectral analysis showed that wave damping was not frequency-dependent for wave frequencies close to the peak frequency. The wave transmission coefficients of a floating kelp farm with about 100 culture lines and with an extension of approximately 200 m were similar to those of submerged detached breakwaters with a relative crest freeboard smaller than −0.4. Furthermore, the bulk drag coefficient of near-surface idealized floating kelp farms can be modelled as a function of the Keulegan-Carpenter number. This study highlights the potential viability of nature-based solutions such as floating kelp farms for coastal protection.
{"title":"Physical modelling study on wave damping induced by an idealized floating kelp farm","authors":"Filipe Miranda , Diogo Mendes , José Miguel Castro , Paulo Rosa-Santos , Francisco Taveira-Pinto , Tiago Fazeres-Ferradosa","doi":"10.1016/j.coastaleng.2024.104648","DOIUrl":"10.1016/j.coastaleng.2024.104648","url":null,"abstract":"<div><div>A physical modelling study was carried out to investigate random wave damping promoted by an idealized floating kelp farm. The experimental conditions spanned intermediate water depths and both linear and nonlinear water waves. Unlike previous studies of wave damping promoted by vegetation, the floating kelp farm was placed close to the water surface with a ratio between vegetation height and water depth close to 0.25. The wave transmission coefficient induced by the floating kelp farm ranged between 0.56 and 0.96. This coefficient decreased for longer floating kelp farms and it was a function of the ratio between kelp farm length and incident wavelength and of the relative wave depth. Spectral analysis showed that wave damping was not frequency-dependent for wave frequencies close to the peak frequency. The wave transmission coefficients of a floating kelp farm with about 100 culture lines and with an extension of approximately 200 m were similar to those of submerged detached breakwaters with a relative crest freeboard smaller than −0.4. Furthermore, the bulk drag coefficient of near-surface idealized floating kelp farms can be modelled as a function of the Keulegan-Carpenter number. This study highlights the potential viability of nature-based solutions such as floating kelp farms for coastal protection.</div></div>","PeriodicalId":50996,"journal":{"name":"Coastal Engineering","volume":"195 ","pages":"Article 104648"},"PeriodicalIF":4.2,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142652932","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-24DOI: 10.1016/j.coastaleng.2024.104647
Wen Deng , Tania Kenyon , Karen Eigeland , David P. Callaghan , Tom E. Baldock
Climate change is amplifying the intensity of severe weather events, with coastal regions such as coral reefs facing heightened vulnerability to cyclonic wave forces. Structural models to predict bending stress and breakage of corals have been developed for coral colonies to enhance comprehension and prediction of the effects of hydrodynamic disturbances on coral reefs. However, there is scope for improving these predictions by evolving the methodology for quantifying complicated and variable coral morphologies. This study aims to predict breakage thresholds for two of the most prevalent coral morphologies: branching and plate corals (using Acropora muricata and Acropora hyacinthus as study species). Laboratory and field measurements were taken to assess coral morphologies and material characteristics. Morphological features of 47 branching colonies and 100 plate colonies were surveyed at the study site (Heron Reef, southern GBR) and the tensile strength of 80 coral samples was obtained by in situ and laboratory testing. Three-dimensional structural models of branching and plate coral colonies were developed, encompassing multiple coral colonies with varying morphological patterns from relatively shallow (5–7 m) to deep (9–12 m) zones. Model results were calibrated and verified with existing data, revealing that velocity thresholds of 1.7 m/s and 5.0 m/s would destroy 90% of the simulated branching coral structures growing in the deep and shallow parts of the forereef zone, respectively. In contrast, the plate corals have sufficient margins of safety even in extreme flow conditions (7 m/s). Additionally, skeletal strength and structural performance were adjusted based on varying degrees of bioerosion inside the coral skeleton. A higher probability of breakage was observed as the extent of bioerosion increased. The laboratory experiments of hydrodynamic loads on coral colony show that the sheltering effect due to one or two neighbouring colonies in the upwave direction is negligible. These models can be easily adjusted to provide predictions for other coral species, shapes, levels of bioerosion, and locations (e.g., sheltered or exposed areas). Comprehensive predictions about the level of expected damage and rubble generation in different areas can be used in reef management planning and restoration prioritization.
{"title":"Structural and hydrodynamic modelling of the probability of breakage of branching and plate coral colonies","authors":"Wen Deng , Tania Kenyon , Karen Eigeland , David P. Callaghan , Tom E. Baldock","doi":"10.1016/j.coastaleng.2024.104647","DOIUrl":"10.1016/j.coastaleng.2024.104647","url":null,"abstract":"<div><div>Climate change is amplifying the intensity of severe weather events, with coastal regions such as coral reefs facing heightened vulnerability to cyclonic wave forces. Structural models to predict bending stress and breakage of corals have been developed for coral colonies to enhance comprehension and prediction of the effects of hydrodynamic disturbances on coral reefs. However, there is scope for improving these predictions by evolving the methodology for quantifying complicated and variable coral morphologies. This study aims to predict breakage thresholds for two of the most prevalent coral morphologies: branching and plate corals (using <em>Acropora muricata</em> and <em>Acropora hyacinthus</em> as study species). Laboratory and field measurements were taken to assess coral morphologies and material characteristics. Morphological features of 47 branching colonies and 100 plate colonies were surveyed at the study site (Heron Reef, southern GBR) and the tensile strength of 80 coral samples was obtained by <em>in situ</em> and laboratory testing. Three-dimensional structural models of branching and plate coral colonies were developed, encompassing multiple coral colonies with varying morphological patterns from relatively shallow (5–7 m) to deep (9–12 m) zones. Model results were calibrated and verified with existing data, revealing that velocity thresholds of 1.7 m/s and 5.0 m/s would destroy 90% of the simulated branching coral structures growing in the deep and shallow parts of the forereef zone, respectively. In contrast, the plate corals have sufficient margins of safety even in extreme flow conditions (7 m/s). Additionally, skeletal strength and structural performance were adjusted based on varying degrees of bioerosion inside the coral skeleton. A higher probability of breakage was observed as the extent of bioerosion increased. The laboratory experiments of hydrodynamic loads on coral colony show that the sheltering effect due to one or two neighbouring colonies in the upwave direction is negligible. These models can be easily adjusted to provide predictions for other coral species, shapes, levels of bioerosion, and locations (e.g., sheltered or exposed areas). Comprehensive predictions about the level of expected damage and rubble generation in different areas can be used in reef management planning and restoration prioritization.</div></div>","PeriodicalId":50996,"journal":{"name":"Coastal Engineering","volume":"195 ","pages":"Article 104647"},"PeriodicalIF":4.2,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142587338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-23DOI: 10.1016/j.coastaleng.2024.104644
S.P. Viaña-Borja , R. González-Villanueva , I. Alejo , R.P. Stumpf , G. Navarro , I. Caballero
Coastal zones are strategic environments of high socioeconomic, political, and ecological value, with over half of the world's population residing within 200 km of the coast. This proximity highlights their vulnerability to extreme events, which are exacerbated by global changes, leading to significant coastal impacts such as erosion, flooding, and ecosystem services deterioration. Consequently, efficient and operational methodologies for continuous monitoring are urgently needed to face these challenges. Bathymetric data are essential for understanding coastal dynamics, yet traditional data collection methods are often constrained by logistical challenges and high costs. Spaceborne remote sensing techniques offer significant advantages over traditional ground-based methods, particularly in terms of cost-effectiveness and operational efficiency. Over the last half-century, different Satellite-derived bathymetry (SDB) methodologies have been developed; however, challenges still persist. In this research, we applied a robust SDB methodology to three different study sites: Cíes Islands, Baiona Bay, and Vao beach within the Ría de Vigo, Galicia (NW Spain). These areas offer diverse and complex mesotidal environments to test for the very first time the methodology's efficacy. SDB was retrieved with a median absolute error (MedAE) ranging from 0.35 m to 1.55 m for depths up to 14 m. Results with different data source were evaluated, obtaining MedAE for nautical charts ranging from 0.46 m to 1.55 m. The precision between the data sources were quite close. In addition, multi-image composite was generated using images coinciding with both low tide (LT) and high tide (HT) conditions across the three zones. The lowest MedAE values were consistently obtained in images classified as LT (0.46 m) corresponding to Vao area. The results highlight the potential of nautical charts as a reliable source of calibration data for SDB, confirm the effectiveness of multi-image and switching models to correct artifacts and turbidity, considering tidal effects, improving single image approaches, and leverage visible bands for precise depth retrieval under varying conditions.
{"title":"Satellite-derived bathymetry using Sentinel-2 in mesotidal coasts","authors":"S.P. Viaña-Borja , R. González-Villanueva , I. Alejo , R.P. Stumpf , G. Navarro , I. Caballero","doi":"10.1016/j.coastaleng.2024.104644","DOIUrl":"10.1016/j.coastaleng.2024.104644","url":null,"abstract":"<div><div>Coastal zones are strategic environments of high socioeconomic, political, and ecological value, with over half of the world's population residing within 200 km of the coast. This proximity highlights their vulnerability to extreme events, which are exacerbated by global changes, leading to significant coastal impacts such as erosion, flooding, and ecosystem services deterioration. Consequently, efficient and operational methodologies for continuous monitoring are urgently needed to face these challenges. Bathymetric data are essential for understanding coastal dynamics, yet traditional data collection methods are often constrained by logistical challenges and high costs. Spaceborne remote sensing techniques offer significant advantages over traditional ground-based methods, particularly in terms of cost-effectiveness and operational efficiency. Over the last half-century, different Satellite-derived bathymetry (SDB) methodologies have been developed; however, challenges still persist. In this research, we applied a robust SDB methodology to three different study sites: Cíes Islands, Baiona Bay, and Vao beach within the Ría de Vigo, Galicia (NW Spain). These areas offer diverse and complex mesotidal environments to test for the very first time the methodology's efficacy. SDB was retrieved with a median absolute error (MedAE) ranging from 0.35 m to 1.55 m for depths up to 14 m. Results with different data source were evaluated, obtaining MedAE for nautical charts ranging from 0.46 m to 1.55 m. The precision between the data sources were quite close. In addition, multi-image composite was generated using images coinciding with both low tide (LT) and high tide (HT) conditions across the three zones. The lowest MedAE values were consistently obtained in images classified as LT (0.46 m) corresponding to Vao area. The results highlight the potential of nautical charts as a reliable source of calibration data for SDB, confirm the effectiveness of multi-image and switching models to correct artifacts and turbidity, considering tidal effects, improving single image approaches, and leverage visible bands for precise depth retrieval under varying conditions.</div></div>","PeriodicalId":50996,"journal":{"name":"Coastal Engineering","volume":"195 ","pages":"Article 104644"},"PeriodicalIF":4.2,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142573347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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