Coastal Model Research Articles

Satellite optical imagery in Coastal Engineering

This Short Communication provides a Coastal Engineering perspective on present and emerging capabilities of satellite optical imagery, including real-world applications that can now be realistically implemented from the desktop. Significantly, at the vast majority of locations worldwide, satellite remote sensing is currently the only source of information to complement much more limited in-situ instrumentation for land and sea mapping, monitoring and measurement. Less well recognised is that publicly available, routinely sampled and now easily accessible optical imagery covering virtually every position along the world's coastlines already spans multiple decades. In the past five years the common obstacles of (1) limited access to high-performance computing and (2) specialist remote sensing technical expertise, have been largely removed. The emergence of several internet-accessible application programming interfaces (APIs) now enable applied users to access petabytes of satellite imagery along with the necessary tools and processing power to extract, manipulate and analyse information of practical interest. Following a brief overview and timeline of civilian Earth observations from space, satellite-derived shorelines (SDS) and satellite-derived bathymetry (SDB) are used to introduce and demonstrate some of the present real-world capabilities of satellite optical imagery most relevant to coastal professionals and researchers. These practical examples illustrate the use of satellite imagery to monitor and quantify both engineered and storm-induced coastline changes, as well as the emerging potential to obtain seamless topo/bathy surveys along coastal regions. Significantly, timescales of satellite-derived changes at the coast can range from decades to days, with spatial scales of interest extending from individual project sites up to unprecedented regional and global studies. While we foresee the uptake and routine use of satellite-derived information becoming quickly ubiquitous within the Coastal Engineering profession, on-ground observations are – and in our view will remain - fundamentally important. Compared to precision in-situ instrumentation, present intrinsic limitations of satellites are their relatively low rates of revisit and decimetre spatial accuracy. New satellite advances including ‘video from space’ and the potential to combine Earth observation with numerical and data-driven coastal models through assimilation and artificial intelligence are advances that we foresee will have future major impact in Coastal Engineering.

The Change in Elevation, Land Subsidence and Local Sea Level Rise Using Coastal Response Model in Jakarta

The rapid urban development activities on the coast of Jakarta has a major impact on the risk of land subsidence. This land subsidence causes significant changes in land elevation. Especially, the coastal areas of Jakarta receive the risk of inundation. The primary purpose of this research was to examine the responses of Jakarta coastal areas based on land subsidence rates of a 24-day baseline data of SAR Sentinel 1A, and local sea-level rise prediction from MOTIWALI data. The methods used in this research were an interferometric SAR (InSAR) and Coastal Response Models. The results of this study indicate that the coastal model response using adjusted elevation based on interferogram elevation and land subsidence rates of SAR Sentinel A1 in a relatively short time (monthly) escalates the evaluation of areas with potential undergoing inundation impacts. Jakarta coastal area receives a greater response with changes in the elevation adjustment based on the local sea-level rise of 0.54 m and land subsidence rates of 0.02. The model demonstrates that the coastal landscape of Jakarta was not possessing the capacity to respond to sea-level rise. Coastal dikes are quite effective as an initial defense in the event of extreme sea waves. The coastal response model using SAR Sentinel 1A data can respond to resource management decisions in coastal areas, and improve assessments quickly that consider the impacts of future land subsidence and local sea-level rise.

Integrated Hydraulic Modelling, Water Quality Modelling and Habitat Assessment for Sustainable Water Management: A Case Study of the Anyang-Cheon Stream, Korea

Recent ecological stream restoration projects have focused on expanding the water-friendly space of streams, promoting the health of aquatic ecosystems, and restoring various habitats, which raise the need for relevant research. Applying integrated environmental analysis, this study quantifies the change in hydraulic characteristics before and after the restoration projects through physical habitat simulation and links the results of physical impacts to estimate benefits of increase in water quality and aquatic ecosystem health due to the implementation of the project. For this, the study area is a 3.3 km long reach of the Anyang-cheon Stream, Korea. Field monitoring revealed that five fish species are dominant and sub-dominant, and account for 76% of the total fish community. To assess the change of before and after ecological stream restoration project, the River2D and Coastal Modelling System (CMS)-Flow 2D models were used for hydraulic and water quality simulations, respectively. For the habitat simulation, the HSI (Habitat Suitability Index) model was used. In addition, the Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI) was used to calculate changes in water quality index and to examine changes in habitat areas with an integrated quantitative index, the methodology of Zingraff-Hamed et al. was adopted. It was found that the ecological stream restoration project significantly increased for the eco-friendly area. In addition, the changes in water quality and habitat suitability grades before the ecological river restoration project were improved to two stages and one stage, respectively. This study applied the integrated analytical framework as a policy/project assessment tool and the results of this study will be useful for the integrated water management policy.

Evolution of the Beaches in the Regional Park of Salinas and Arenales of San Pedro del Pinatar (Southeast of Spain) (1899–2019)

Coastal erosion is anissuewhich affects beaches all over the world and that signifies enormous economic and environmental losses. Classed as a slow phenomenon, the evolution of the coastline requires long-term analysis. In this study, old cartography and aerial photographs from various dates have been used to study the evolution of the coastline. The information has been processed with free software (QGIS) and for the calculation of sediment transport the Coastal Modeling System (SMC) software. The results show the accretion/erosion phenomena that occurred after the construction of the port in San Pedro del Pinatarin 1954 and which changed the coastal dynamics of a highly protected area. In some sectors, the beach has been reduced almost in its entirety, with retreat rates of up to −2.05 m per year and a total area loss of 66,419.81 m2 in Las Salinas beach and 76,891.13 m2 on Barraca Quemada beach.

CMEMS-Based Coastal Analyses: Conditioning, Coupling and Limits for Applications

Recent advances in numerical modeling, satellite data, and coastal processes, together with the rapid evolution of CMEMS products and the increasing pressures on coastal zones, suggest the timeliness of extending such products toward the coast. The CEASELESS EU H2020 project combines Sentinel and in-situ data with high-resolution models to predict coastal hydrodynamics at a variety of scales, according to stakeholder requirements. These predictions explicitly introduce land discharges into coastal oceanography, addressing local conditioning, assimilation memory and anisotropic error metrics taking into account the limited size of coastal domains. This article presents and discusses the advances achieved by CEASELESS in exploring the performance of coastal models, considering model resolution and domain scales, and assessing error generation and propagation. The project has also evaluated how underlying model uncertainties can be treated to comply with stakeholder requirements for a variety of applications, from storm-induced risks to aquaculture, from renewable energy to water quality. This has led to the refinement of a set of demonstrative applications, supported by a software environment able to provide met-ocean data on demand. The article ends with some remarks on the scientific, technical and application limits for CMEMS-based coastal products and how these products may be used to drive the extension of CMEMS toward the coast, promoting a wider uptake of CMEMS-based predictions.

Shoreline Solutions: Guiding Efficient Data Selection for Coastal Risk Modeling and the Design of Adaptation Interventions

The Caribbean is affected by climate change due to an increase in the variability, frequency, and intensity of extreme weather events. When coupled with sea level rise (SLR), poor urban development design, and loss of habitats, severe flooding often impacts the coastal zone. In order to protect citizens and adapt to a changing climate, national and local governments need to investigate their coastal vulnerability and climate change risks. To assess flood and inundation risk, some of the critical data are topography, bathymetry, and socio-economic. We review the datasets available for these parameters in Jamaica (and specifically Old Harbour Bay) and assess their pros and cons in terms of resolution and costs. We then examine how their use can affect the evaluation of the number of people and the value of infrastructure flooded in a typical sea level rise/flooding assessment. We find that there can be more than a three-fold difference in the estimate of people and property flooded under 3m SLR. We present an inventory of available environmental and economic datasets for modeling storm surge/SLR impacts and ecosystem-based coastal protection benefits at varying scales. We emphasize the importance of the careful selection of the appropriately scaled data for use in models that will inform climate adaptation planning, especially when considering sea level rise, in the coastal zone. Without a proper understanding of data needs and limitations, project developers and decision-makers overvalue investments in adaptation science which do not necessarily translate into effective adaptation implementation. Applying these datasets to estimate sea level rise and storm surge in an adaptation project in Jamaica, we found that less costly and lower resolution data and models provide up to three times lower coastal risk estimates than more expensive data and models, indicating that investments in better resolution digital elevation mapping (DEM) data are needed for targeted local-level decisions. However, we also identify that, with this general rule of thumb in mind, cost-effective, national data can be used by planners in the absence of high-resolution data to support adaptation action planning, possibly saving critical climate adaptation budgets for project implementation.

Hurricane Scenario Generation for Uncertainty Modeling of Coastal and Inland Flooding

Hurricanes often induce catastrophic flooding due to both storm surge near the coast, and pluvial and fluvial flooding further inland. In an effort to contribute to uncertainty quantification of impending flood events, we propose a probabilistic scenario generation scheme for hurricane flooding using state-of-art hydrological models to forecast both inland and coastal flooding. The hurricane scenario generation scheme incorporates locational uncertainty in hurricane landfall locations. For an impending hurricane, we develop a method to generate multiple scenarios by the predicated landfall location and adjusting corresponding meteorological characteristics such as precipitation. By combining inland and coastal flooding models, we seek to provide a comprehensive understanding of potential flood scenarios for an impending hurricane. To demonstrate the modeling approach, we use real-world data from the Southeast Texas region in our case study.

Seismic and Coastal Vulnerability Assessment Model for Buildings in Chile

This article proposes a vulnerability assessment model for evaluating buildings’ expected seismic performance, as well as their vulnerability to tsunamis. The objective of this assessment is to provide appropriate information for decision makers regarding the need of repairs and reinforcement of buildings or other mitigation measures that need to be applied in a territory. A procedure for assessing seismic vulnerability and another methodology for evaluating tsunami vulnerability faced by coastal structures is presented. Finally, a method that integrates both procedures is proposed, providing a combined index of vulnerability. The assessment model was applied to the central area of the city of Talcahuano, Chile, which was affected by the 2010 Maule earthquake and tsunami.

A novel coastal landscape model for sandy systems

A common measure to mitigate erosion along sandy beaches is the implementation of sand nourishments. The design and societal acceptance of such a soft mitigation measure demands information on the expected evolution at various time scales ranging from a storm event to multiple decades. Process-based morphodynamic models are increasingly applied to obtain detailed information on temporal behaviour. This paper discusses the process-based morphodynamic model applied to the Sand Motor and how the morphodynamic forecasts have benefitted from the findings of an interdisciplinary research program called NatureCoast. The starting point is the morphodynamic prediction of the Sand Motor made for an Environmental Impact Assessment in 2008 before construction began. After the construction, the model computations were optimized using the first-year field measurements and insights by applying advanced model features. Next, an integrated model was developed that seamlessly predicts the morphodynamics in both the subaqueous and subaerial domains of the Sand Motor. Decadal predictions illustrate the need to be able to resolve the marine and aeolian processes simultaneously in one modelling framework in the case of dynamic coastal landscapes. Finally, a novel morphodynamic acceleration technique was developed that allows for predicting the morphodynamics for multiple decades while incorporating storm events in one simulation. Combining the above-mentioned developments has led to a unique, open-source, process-based landscape tool for (complex) coastal sandy systems, which can stimulate further collaboration between research communities. Moreover, this work demonstrates the evolution from mono- to interdisciplinary forecasts of coastal evolution.

Modelling an energetic tidal strait: investigating implications of common numerical configuration choices

Representation of the marine environment is key for reliable coastal hydrodynamic models. This study investigates the implications of common depth-averaged model configuration choices in sufficiently characterising seabed geometry and roughness. In particular, applications requiring a high level of accuracy and/or exhibiting complex flow conditions may call for greater detail in marine environment representation than typically adopted in coastal models. Ramsey Sound, a macrotidal strait in Pembrokeshire, Wales, UK is considered as a case study. The site contains various steeply inclined bathymetric features, including a submerged pinnacle named Horse Rock and a rocky reef called “The Bitches”. The available energy in Ramsey Sound’s tidal currents has attracted attention from tidal energy developers. There is interest in accurately modelling the energetic hydrodynamics surrounding its pronounced bathymetry. The coastal flow solver Thetis is applied to simulate the flow conditions in Ramsey Sound. It is shown that notable prominent bathymetric features in the strait influence localised and, most importantly, regional hydrodynamic characteristics. “The Bitches” consistently accelerate flow in the strait while Horse Rock induces a notable wake structure and flow reversals. The model is calibrated against bed- and vessel-mounted Acoustic Doppler Current Profiler (ADCP) observations, by altering seabed roughness parameterisations. A spatially variable and locally scaled Manning coefficient based on diverse seabed classification observations is found to improve model performance in comparison to uniformly applied constants, the latter a more common approach. The local impact of altering the Manning coefficient configuration is found to be greatest during spring flood periods of high velocity currents. Meanwhile, the effect of coarsening the computational mesh around bathymetric features towards values more typically applied in coastal models is investigated. Results indicate severe misrepresentation of seabed geometry and subsequent wake hydrodynamics unless refined to a mesh element size that adequately represents Horse Rock and “The Bitches”.

Mangrove Forest Management Model at Payum Merauke Beach

The implementation of the coastal resource management model must be adjusted to the characteristics of the coastal communities in the coastal area. This study aims to analyze the management model of mangrove forests in Payum Beach. The research location is Payum coastal area, samkai village, Merauke district. The population in this study are coastal communities, traditional leaders and stakeholders associated with mangrove forest management. Sampling uses a purposive sampling technique, which will be adjusted to the information needs of the study. Data collected includes mangrove forest management. Data analysis using descriptive qualitative. The results showed that there was cooperation between coastal communities and the government in carrying out mangrove rehabilitation in the process the government tended to only inform the community about the decisions that would be made. The management of mangrove forests on Payum beach adopts an instructive co-management management model.

Responses of two fringing salt marsh plant species along a wave climate gradient

Salt marshes are increasingly valued for their role in coastal defense. In particular, marsh plants slow the progression of waves, thereby decreasing wave heights, orbital velocities and associated energy. Practical application of these effects has driven substantial research estimating the effects of plants on waves. However, the effects of waves on plants remain understudied, especially regarding plant responses along a wave climate gradient. To begin to understand these responses, we collected above- and belowground plant data and wave data from 60 sites across Mobile Bay, USA, and tributaries and evaluated plant responses along the range of assessed wave climate conditions. Plant responses among the dominant species, Juncus roemerianus and Spartina alterniflora, varied along the wave climate gradient. However, the basal diameter of shoots in both species declined linearly with increasing wave climate. While wave climate had no observable effect on other S. alterniflora parameters, the declining diameter of J. roemerianus shoots along the same gradient was commensurate with a decline in the percentage of live canopy shoots aboveground and an increase in root and rhizome biomass in the active rooting zone belowground. In contrast to previous studies, other responses including the height, biomass and density of aboveground shoots in both species were not related to wave climate. More broadly, these results demonstrate that plant features important for wave attenuation such as shoot diameter can change in response to varying wave conditions. These feedbacks should be incorporated to improve coastal modeling and successes of coastal conservation, restoration and enhancement projects.

GCOAST: Skill assessments of coupling wave and circulation models (NEMO-WAM)

The coupling of models is a commonly used approach when addressing the complex interactions between different components of the Earth system. This study presents the development of a new, high -resolution, coupled ocean and wave model system for the North Sea and the Baltic Sea, which is part of the Geestacht COAstal model SysTem GCOAST. We focus on the nonlinear feedback between strong tidal currents and wind -waves, which can no longer be ignored, in particular in the coastal zone where its role seems to be dominant. The proposed coupling parameterisations account for the feedback between of the upper ocean on the atmospheric circulation by accounting for the effects of the sea level, and ocean temperature and salinity. A focus is given on the newly implemented parameterisations that consider the effect of non-liner contribution and the component transfer of the momentum and energy fluxes from the atmosphere to the ocean thought the waves interface. Sensitivity experiments are performed to estimate the role of different wave-ocean coupling components. The performance of the coupled modelling system is illustrated for the cases of several extreme events. For example, the inclusion of wave coupling changes sea surface temperature, the mixing and ocean circulation and the total sea level leading to better agreement with in -situ and satellite observations. The model comparisons with data from satellite altimeter and in-situ observations showed that the use of the fully coupled system reduces the errors, especially under severe storm conditions.

Impacts of deep-water spills on mesopelagic communities and implications for the wider pelagic food web

Mesopelagic fishes link lower trophic levels and higher predators, as well as production at the surface to the deep sea. Mesopelagic fish may be vulnerable to deep entrained oil plumes of the type seen in the 2010 Deepwater Horizon spill; even at low concentrations, exposure to polycyclic aromatic hydrocarbons (PAHs) may cause lethal and sublethal effects, such as endocrine disruption, growth inhibition, and genetic damage. A reduction in the abundance of mesopelagic fish could potentially shift predation pressure by large pelagics to epipelagic forage or other species, with potential fisheries consequences. We explored this hypothesis on the West Florida Shelf using an Atlantis model for the Gulf of Mexico. Atlantis is a 3-dimensional, spatially explicit marine and coastal modeling framework that incorporates multiple submodels integrating biophysical, chemical, ecological, and fisheries dynamics. We found that biomass, trophic niche width, and predation mortality exerted by mesopelagic predators showed small but varied responses across different contributions of mesopelagics to predator fish diet under oil impacts. We observed shifts in the diet of pelagic predators with increasing availability of mesopelagic fish prey, suggesting that pelagic fish predator populations are more vulnerable to oil exposure if they are tightly coupled to the mesopelagic food web. These results suggest that when measured at the population level, oil-spill impacts may be harder to detect due to the response of individual fish species.

SUBGRID NUMERICAL MODELING OF TSUNAMI AND STORM SURGE INUNDATION IN A COASTAL URBAN SETTING

An experiment using a physical model of a coastal city was conducted to simulate tsunami and storm surge conditions which may lead to city inundation. The results of the physical experiment were compared with those from a subgrid numerical model based on the shallow water equation using the topography of the physical experiment obtained from LIDAR scanning. The experiment aims to provide a better understanding on the variation of tsunami or storm surge inundation level at different locations of the city due to the ground elevation, building arrangement, and shielding effects. The result from this experiment will serve to increase the accuracy of coastal numerical models and revise the current hazard maps and evacuation plans.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/k4v5EotRpfg

BEACH SLOPES FROM SATELLITE-DERIVED SHORELINES

The slope of the beach face is a critical parameter for coastal scientists and engineers studying sandy coastlines. However, despite its importance for coastal applications (engineering formulations, coastal flood modelling, swimming safety), it remains extremely difficult to obtain reliable estimates of the beachface slope over large spatial scales (hundreds to thousands of km of coastline). This presentation describes a new method to estimate the beach-face slope exclusively from space-borne observations: shoreline positions derived from publicly available optical imaging satellites and tide heights from satellite altimetry. This new technique is first validated against field measurements and then applied across hundreds of beaches in eastern Australia and California, USA (data available at http://coastsat.wrl.unsw.edu.au/).Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/U9zMbFX4gPk

CHALLENGES OF BOUNDARY CONDITIONS IN OPEN OCEAN MODELS

The development and calibration of coastal numerical models to support engineering design and environmental impact studies is a challenging process and one that requires professional judgement and continual assessment of all aspects of the model makeup. Fundamental to the integrity of the model are appropriate boundary conditions and quality observational data for calibration. Open ocean boundary conditions are typically the most complex and important aspect of a model build. They represent the influence of dynamics occurring beyond the model extent, bridging large-scale dynamics to the small-scale processes in the model. This study discusses the challenges of open ocean boundaries and how we utilised data to achieve an effective model.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/evL7f_17wZg

COMBINING DATA-DRIVEN AND NUMERICAL MODELLING APPROACHES TO STORM EROSION PREDICTION

Physics-based numerical models play an important role in the estimation of storm erosion, particularly at beaches for which there is little historical data. However, the increasing availability of pre-and post-storm data for multiple events and at a number of beaches around the world has opened the possibility of using data-driven approaches for erosion prediction. Both physics-based and purely data-driven approaches have inherent strengths and weaknesses in their ability to predict storm-induced erosion. It is vital that coastal managers and modelers are aware of these trade-offs as well as methods to maximise the value from each modelling approach in an increasingly data-rich environment. In this study, data from approximately 40 years of coastal monitoring at Narrabeen-Collaroy Beach (SE Australia)has been used to evaluate the individual performance of the numerical erosion models SBEACH and XBeach, and a data-driven modelling technique. The models are then combined using a simple weighting technique to provide a hybrid estimate of erosion.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/v53dZiO8Y60

DO WE NEED PRE-STORM SURVEYED BATHYMETRY FOR OPERATIONAL EROSION FORECASTING? EVALUATION OF REPRESENTATIVE AND SYNTHETIC BATHYMETRY ALTERNATIVES

Immediate pre-storm bathymetry is a key input required for numerical models used in coastal hazard Early Warning Systems. However, the expense and challenging nature of hydrographic surveying means that the availability of high-quality data is extremely rare. This study evaluates the extent to which synthetic and representative bathymetry alternatives can be used to obtain reliable predictions of storm induced sub-aerial erosion using the XBeach coastal erosion numerical model. Multiple storm events at 2 contrasting sites are modelled using 6 bathymetry scenarios including pre-storm surveyed bathymetries, an average bathymetry, and Dean profiles. The output is analysed to evaluate the skill of XBeach erosion predictions as a function of the bathymetry used.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/bE3aXVXxZqQ

NEW SUSPENDED SAND CONCENTRATION MODEL FOR BREAKING WAVES

Process-based morphodynamic modelling suites (as well as other process-based models) are often considered to be inefficient and unsuitable for simulating medium- to long-term morphodynamics due to the various theoretical (e.g. robustness of sediment transport models) and practical (e.g. computational costs) limitations. In particular, a lack of knowledge of sediment transport processes and how they relate to hydrodynamics makes the application of short-term models to long-term coastal evolution challenging. Even the state-of-the-art coastal area modelling suites (such as Delft3D and MIKE21) consist of relatively simple physics, relying instead on numerous semi-empirical parameterizations, which are often poorly supported by measured data and/or physical process understanding. In particular, suspended sediment transport in the highly turbulent surf zone is poorly modelled under breaking wave conditions. Six existing suspended sand concentration (SSC) models were critically evaluated against four high-resolution datasets with field-scale breaking waves and co-located velocity and concentration measurements over multiple cross-shore zones (shoaling, breaking and inner-surf zones). A new improved concentration model was proposed based on a novel empirical relationship observed between local water depth and reference concentration, as well as latest process understanding and insights.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/2iBrnXs4b3M