Worldwide, communities are facing increasing flood risk, due to more frequent and intense hazards and rising exposure through more people living along coastlines and in flood plains. Nature-based Solutions (NbS), such as mangroves, and riparian forests, offer huge potential for adaptation and risk reduction. The capacity of trees and forests to attenuate waves and mitigate storm damages receives massive attention, especially after extreme storm events. However, application of forests in flood mitigation strategies remains limited to date, due to lack of real-scale measurements on the performance under extreme conditions. Experiments executed in a large-scale flume with a willow forest to dissipate waves show that trees are hardly damaged and strongly reduce wave and run-up heights, even when maximum wave heights are up to 2.5 m. It was observed for the first time that the surface area of the tree canopy is most relevant for wave attenuation and that the very flexible leaves limitedly add to effectiveness. Overall, the study shows that forests can play a significant role in reducing wave heights and run-up under extreme conditions. Currently, this potential is hardly used but may offer future benefits in achieving more adaptive levee designs.

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Seaport operability is key to the economic viability of ports. Metocean conditions (e.g., wind, short waves, and infragravity waves) affect this operability when certain thresholds are exceeded. This paper describes a method for the global mapping of seaport operability risk indicators using open-source metocean data. This global-scale assessment provides a geographic overview of operability risks and first-order insights into the most relevant metocean risk indicators at each location. The results show that locations around the equator and inland seas have lower operability risk than locations farther away from the equator. “Hotspots” are mainly located along the southern capes (Cape of Good Hope, Leeuwin, Horn), around the ‘Roaring Forties’, and at exposed locations along the oceans. Of the metocean parameters considered, short waves are found to be the most critical risk indicator for port operability at most locations. Using (the insights of) this study, port authorities, operators, and designers can prepare for metocean risks at an early stage and effectively respond with mitigation measures and layout adjustments to improve port operability.

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In Africa, several new seaport developments are being considered. In sedimentary environments, such port developments can have adverse impacts on the evolution of adjacent coastlines. To learn from past port engineering practice, we created a unique database containing the coastline evolution and characteristics of 130 existing African seaports. Whereas the systematic mapping of coastal impacts was previously hampered by data availability, innovative automated satellite image processing techniques have enabled us to intercompare ports at an unprecedented continental scale. We found large geographical differences with respect to the beach evolution. The total detected changes in the beach area between 1984 and 2018 totaled 44 km2, of which ca. 23 km2 is accretion and ca. 21 km2 is erosion. The top 10% “hotspot” ports account for more than 65% of these changes. These hotspots exhibit common characteristics, namely: they are located on open coastlines, have large alongshore sediment transport potential, and have large cross-shore breakwaters. Although these driving characteristics are well established in coastal engineering theory, our results indicate that the beaches adjacent to the existing seaports have been and remain seriously affected by these drivers. Our results can be used to inform beach maintenance strategies for existing seaports and to support planners and engineers to minimize long-term coastal impacts of port expansions and new port developments in Africa in the future.
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To guarantee port accessibility, navigation approach channels need to be well maintained. Annual dredging efforts to maintain navigable channels may well exceed tens of millions m³ of sediment per year, which results in high recurrent costs for port operators. Quantification of expected siltation rates with process-based numerical models helps to effectively design and optimise approach channels. The setup of such models requires several assumptions and parameter settings which introduce uncertainty in model output. However, traditional Monte Carlo methods to quantify that uncertainty in model output are often too resource-intensive with current standard computer resources to be feasibly applied in coastal engineering projects such as approach channel design. Here, we use an alternative multifidelity approach to estimate the probability density function of channel siltation, at lower computational costs compared to direct Monte Carlo simulation. The idea behind this method is to map the output uncertainty of a faster, but inaccurate model to a preferred high-detailed model. The key requirement is that the faster, low-fidelity model and the detailed high-fidelity model are correlated, and that his correlation can be modelled with a probabilistic function. Since linearity of the correlation is not a requirement, the coarse-grid model can be very inaccurate but still serve as an adequate predictor of the high-fidelity model. In this study we did observe a highly nonlinear correlation, which in our case is explained by underestimation of channel siltation near the surf zone by the coarse model. In the presented multifidelity approach we adopted a combination of quasi-random Monte Carlo simulation and a non-parametric Gaussian process transfer function to estimate the uncertainty of total siltation and spatial patterns of siltation in a port approach channel. We argue that the multifidelity approach is conceptually straightforward and found that it can be used to significantly decrease the costs of probabilistic analysis; in our case we found a 85% decrease compared to direct Monte Carlo simulation. An additional advantage is that the approach allows for a trade-off between precision and efficiency by varying the number of high-fidelity model runs. Therefore, we conclude that the multifidelity framework is a potential powerful alternative for cases in which direct Monte Carlo simulation is infeasible or undesirable.

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In process-based numerical models, reducing the amount of input parameters, known as input reduction (IR), is often required to reduce the computational effort of these models and to enable long-term, ensemble predictions. Currently, a comprehensive performance assessment of IR-methods is lacking, which hampers guidance on selecting suitable methods and settings in practice. In this study, we investigated the performance of 10 IR-methods and 36 subvariants for wave climate reduction to model the inter-annual evolution of nearshore bars. The performance of reduced wave climates is evaluated by means of a brute force simulation based on the full climate. Additionally, we tested how the performance is affected by the number of wave conditions, sequencing, and duration of the reduced wave climate. We found that the Sediment Transport Bins method is the most promising method. Furthermore, we found that the resolution in directional space is more important for the performance than the resolution in wave height. The results show that a reduced wave climate with fewer conditions applied on a smaller timescale performs better in terms of morphology than a climate with more conditions applied on a longer timescale. The findings of this study can be applied as initial guidelines for selecting input reduction methods at other locations, in other models, or for other domains.

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Long-term sustainable port development requires accounting for the intrinsic values of ecosystems. However, in practice, ecosystem considerations often only enter the planning and design process of ports when required by an Environmental Impact Assessment. At this late stage, most of the design is already fixed and opportunities to minimize and restore ecosystem impacts are limited. In this paper, we adopt a large-scale, ecosystem perspective on port development with the aim to identify ecosystem-based design alternatives earlier and throughout the planning and design of a port's marine infrastructure. We present a framework, termed the 'ecosystem-based port design hierarchy' (EPDH), to identify ecosystem-based alternatives at four hierarchical design levels: 1) alternatives to port developments, 2) port site selection, 3) port layout design, and 4) design of structures and materials. In applying the EPDH framework retrospectively to a case study of port expansion in Tema, Ghana, we establish that ecosystem considerations played only a limited role in identifying and evaluating alternatives at all four design levels in the case study, whereas more eco-friendly alternatives in terms of port layouts, structures, and materials are identified using the EPDH framework. This reveals that opportunities for ecosystem-friendly port designs may have been missed and demonstrates the need for and the potential added value of our framework. The framework can assist practitioners in earlier and wider identification of ecosystem-based alternatives for a port's marine infrastructure in future seaport developments and, hence, represents an important step towards more sustainable port designs.

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Namhangjin beach is protected by multiple submerged breakwaters (SBWs) which were built to protect the ~4 km long sandy beach. A coastline model (UNIBEST) was used to investigate the long term effect of the SBW structures on the beach. The model computes long-term shoreline changes due to coastal structures as a result of the strong longshore sediment transport gradients at the structures. Bathymetry data of the shoreface and nearshore profiles were obtained from a field survey, while wave conditions from offshore WAM hindcast (Wave Modeling Group) were transformed towards the nearshore with the Delft3D+SWAN modelling system. Local wave sheltering by the SBWs was included in the wave model. A situation with and without the SBWs was modelled. A rapid adjustment of the shoreline was observed in the model as a result of the wave conditions in the first two years. After that, the shoreline shape stabilized without significant changes both for the situation with and without SBWs. A smooth curved coastline shape was obtained in the model without SBWs, while the model with SBWs shows a similar overall shoreline shape with undulations of the shoreline shape behind the breakwaters. A similar undulating shoreline was observed in the Sept-2013 imagery at Namhangjin beach. The local accretion behind the SBWs may induce some erosion in the lee area of the SBWs, causing distortions of the shoreline shape. Most sediment accreted at the first SBW (i.e. the northern most SBW where alongshore transport from the North was trapped), while the coastline change rate gradually decreased towards the South. The effectiveness of the SBWs at the considered shoreline section for maintaining the shoreline is somewhat ambiguous as local areas with accretion or erosion are present with respect to the situation without the breakwaters. The results show that multiple SBWs need to be carefully designed to protect beaches as local distortions of the shoreline shape may be present directly downdrift from the structures.@en

Understanding long-term sandbar dynamics can be crucial for informed coastal zone management, but is often hampered by data availability. To increase the number of sandbar observations available from bathymetric surveys, this study proposes and evaluates a method to manually extract the sandbar location using freely available satellite imagery for the case study of Anmok beach in South Korea. Validation of the satellite extracted sandbar locations against 9 in-situ measurements shows good agreement with errors well within the pixel resolution of the satellite imagery (i.e. 30 m for Landsat missions). The applicability of the method is constrained to locations where (1) the cross-shore crescentic length scales are larger than the image resolution, (2) frequent wave breaking and clouds are absent and (3) the water clarity is sufficient to enable the manual extraction of the sandbar crest line. Using the additional sandbar observations from the satellite imagery significantly increases the temporal extent and resolution of the dataset for Anmok beach. This allows the study of sandbar characteristics, dynamics and impacts of human interventions to an extent that would not have been possible without the satellite imagery. Within the study period 1990–2017 it is found that the sandbar maintains a persistent crescentic pattern that is only altered during prolonged and very intense storm conditions. The cumulative alongshore migration of the sandbars is investigated and found to be in the order of hundreds of meters over the 27 years study period. Comparing the sandbar characteristics prior and after the construction of Gangneung port shows that both the amplitudes and wavelengths of the sandbar crescents near the port have decreased after its construction.@en

Measured trends and variability in shoreline position are used by coastal managers, scientists and engineers to understand and monitor coastal systems. This paper presents a new and generic method for automated shoreline detection from the largely unexplored collection of publicly available satellite imagery. The position of the obtained Satellite Derived Shoreline (SDS) is tested for accuracy for 143 images against high resolution in-situ data along a coastal stretch near the Sand Motor, a well-documented mega-scale nourishment along the Dutch coast. In this assessment, we quantify the effects of potential inaccuracy drivers such as the presence of clouds and wave-induced foam. The overall aim of this study is to verify whether the SDS is suitable to study structural coastline trends for coastal engineering practice.

In the ideal case of a cloud free satellite image without the presence of waves, with limited morphological changes between the time of image acquisition and the date of the in-situ measurement, the accuracy of the SDS is with subpixel precision (smaller than 10–30 m, depending on the satellite mission) and depends on intertidal beach slope and image pixel resolution. For the highest resolution images we find an average offset of 1 m between the SDS position and the in-situ shoreline in the considered domain. The accuracy deteriorates in the presence of clouds and/or waves on the image, satellite sensor corrections and georeferencing errors. The case study showed that especially the presence of clouds can lead to a considerable seaward offset of the SDS of multiple pixels (e.g. order 200 m). Wave-induced foam results in seaward offsets in the order of 40 m.

These effects can largely be overcome by creating composite images, which results in a continuous dataset with subpixel precision (10–30 m, depending on the satellite mission). This implies that structural trends can be detected for coastlines that have changed with at least the pixel resolution within the considered timespan.

Given the accuracy of composite images along the Sand Motor in combination with the worldwide availability of public satellite imagery covering the last decades, this technique can potentially be applied at other locations with large (structural) coastline trends.
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Nearshore sandbar patterns can affect the hydrodynamics and, as a result, the beach morphodynamics in the nearshore zone. Hence, spatial and temporal variability in the sandbars can influence beach accretion and erosion. Understanding the variability of the sandbar system can therefore be crucial for informed coastal zone management. So far, the methods to study sandbar dynamics mainly include datasets of video observations or occasional bathymetric surveys. However, at most locations around the world, these types of data are not or only scarcely available. In this paper we present an alternative method to analyze long-term sandbar variability by means of freely available satellite imagery. These images are globally available since the 1980’s and, thus, have the potential to be applicable at any location in the world. Here, we will illustrate the methodology by means of a case study at Anmok beach at the South Korean East coast.@en

Objective Ports are designed for their economic function, i.e., to accommodate trade. Traditionally, engineering perspective prevails in port design and environmental and social aspects are accounted for at a later stage. A growing consensus recognizes the need for sustainable port development, aimed at finding the right balance between economic, social, and ecological aspects. However, sustainability is an easily coined term to which stakeholders and experts give different interpretations or at least set different priorities, often related to their background and interests. A critical element including sustainability in port design process is gaining insight in the meaning of sustainability and in particular how this can be operationalized. In this paper we give insight in stakeholders’ and scientists’ perspectives from an engineering, ecological, governance and economic viewpoint on sustainability in port infrastructure. Furthermore, we discuss how these perspectives can contribute to a more integrated approach, based on co-creation, giving space to disciplines or viewpoints that are traditionally not that much involved. Hence, broader economic and societal values can be included and opportunities identified, rather than considered as institutional constraints. Methodology The research project employs a bottom-up approach involving a wide range of stakeholders directed at the port of Tema, Ghana. To obtain insight in the perspectives of the four disciplines of engineering, ecology, governance and economy and those of stakeholders in the field, the following activities have been conducted: 1.Literature review and desk research over aspects such as sustainability and sustainable port development andeco-system based port designs was carried out. 2.Scoping workshop in 2016 on problem identification in the Port of Tema, in Ghana. 3.Survey and serious game play across scientists and supporting parties of the projects on the meaning of sustainability in ports in general 4.A large workshop and field mission in Tema Harbour in February 2017 with participation of a wide range of local stakeholders. A game structuring approach was followed for generating visions for the future. During the field mission port authorities and scientists have been interviewed. Results/Findings The different viewpoints provide the following priorities: -Engineering: oFirst and foremost, a port should function as a port (i.e. enable transfer of goods). oNeed for this mild conditions and sufficient depth to allow for berthing and navigability -Ecology: oConserve: Preferably, a port does not affect its surroundings: Location choice is critical, whereby scarce locations such as estuaries should be avoided, rather expand than develop new sites and similar sites well protected. Large scale perspective is necessary. Maintain connectivity oCreate: Smart design (eg gradual transfers, variability), and material choice. -Socio-Economic: oUse Ecosystem services basis for the design; specific values include congestion, coastal erosion, spiritual values, employment and housing oSCBA can be critical in convincing policy makers and investors; this includes fast implementation by reducing complaints and legal constraints -Governance: oStakeholder inclusive design allows for broadening the scale and scope of the issue at hand and may lead to new or creative opportunities oPPPs most likely allow for successful implementation and flexibility in the long term Implications for Research/Policy •Learning about the values and knowledge resources of local stakeholders is essential to create system understanding and identify opportunities for creating added value. From a sustainability perspective, ports are no longer considered in isolation but as part of a coastal, societal and transportation system. This directly allows for broadening the scope and scale on which trade-offs are being made and opportunities searched. The search for opportunities , rather than being reactive, distinguishes a sustainability approach from traditional design approaches. •Based on the perspectives of stakeholders conceptual port lay-outs can be developed, including port expansion plans, ‘add-on’ modules, and how to develop a fully stakeholder inclusive design process •Lastly, the stakeholder/expert perspectives enable the development of a set of evaluation criteria to assess proposed lay-outs, and provide insight in prioritization of different criteria categories.@en

A867 Sustainable port development and integrated coastal management (ICM) require: (i) ecosystem-based or integrated design, (ii) a future orientation, (iii) stakeholder-inclusive processes. Stakeholder-inclusive processes, the focus of this paper, increase the diversity of knowledge and the availability of information, and expand the pool of creativity in a development initiative. As such, they address the bounded rationality of a single actor or group of actors with limited information on their coastal (port) system and limited ability to explore and process all potential options for such a system. Stakeholder participation is also considered ‘good governance’, and forms an inherent component of ICM. In this paper we investigate the added value of stakeholder-inclusive processes conducted in the scoping phases of several coastal and port projects in data-poor environments. We evaluate 5 cases: Sustainable port development in Tema (Ghana), ICM in Sao Tome, ICM in Guinee for the island of Kaback, for Grand Bassam (Ivory Coast),and Richards Bay/ Mhlatuze in terms of 7 categories of added value, namely: 1. Data collection/ Ground-truthing: biogeophysical and social aspects 2. System understanding: governance, social and biogeophysical aspects 3. Insight in past and current actions/ strategies 4. Eliciting problem perceptions, values and priorities 5. Developing new solutions/ Creativity: changing scale, issues involved, future visions 6. Process design preferences: who should be involved, how and when 7. Increased support for new coastal and port development strategies. Overall, we determine that although scoping was the primary focus of the cases, the participatory processes contributed to generating potential solution options, and preparing for evaluation and decision making. The range of potential solution options broadened– more issues were identified, and the fit with the local needs improved. The added value of the participatory process is clarified further by comparing with earlier non-participatory initiatives in some of the case studies. Then, the implemented ‘solutions’ came as a surprise to the local community as stakeholders were not engaged, nor informed about the measures that were implemented. Finally, the lessons learned from the case studies regarding the added value of stakeholder inclusive approaches within the scoping phase of ICZM and seaport development projects are linked explicitly to data poor situations. In particular, we find indications that data gathering and ground-truthing and developing a shared system understanding and insights on the effects of past and present actions, are particularly valuable.@en

Connecting to the trend of harmonization of port developments with nature, this paper presents a framework for the explicit inclusion of ecosystem based alternatives in the early planning and design stages of seaport developments. The framework aims to shift the focus from offsetting environmental impacts afterwards to avoidance and reduction of environmental impacts as integral part of seaport planning and design. Our framework, labeled the ecosystem based port design hierarchy, helps to identify ecosystem based alternatives at 4 hierarchical levels of port planning and design: (1) consideration of alternatives to port developments to meet a perceived transport capacity problem (i.e. “no-port” alternatives), (2) port site selection, (3) port layout selection and (4) selection of port structures and materials. Application of the framework to the planning and design process of Tema port expansion in Ghana in hindsight shows that ecosystem based considerations barely played a role in alternative generation and evaluation. Therefore, opportunities for environmental impact avoidance and reduction may have been missed in the decision making process. It is recognized that decision making is a multi-disciplinary and multi-stakeholder process which is not based on environmental considerations only, but requires tradeoffs with functional, operational and socio-economic requirements. Nevertheless, we believe that explicit identification and inclusion of ecosystem based alternatives as part of this decision making process, as supported by our framework, is a requirement to arrive at port developments that are (better) harmonized with nature.@en

A prototype harbour design toolbox has been developed, with a Graphical User Interface, incorporating simple model instruments to rapidly assess the impact of a harbour construction on a coastal environment, such as expected siltation rates and impact on the coastline evolution. The toolbox can be useful for different stakeholders, particularly in the early phases of a harbour development project, to explore order of magnitude impacts, relevant design parameters and dominant processes. This paper will set out the current status of the harbour design toolbox and investigate the benefits of use for specific stakeholders. The ambition is to further extend the harbour design toolbox towards an integral coastal design tool, facilitating the implementation of other type of interventions and linking to other disciplines such as marine ecology and navigation. It is intended that the integral coastal design tool will facilitate a multi-disciplinary approach to aid in the feasibility, design, construction or maintenance phase of coastal development project.

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A study of siltation processes was undertaken for the harbour of Harlingen in the Netherlands, to investigate their relative importance for potential sedimentation. Three distinct harbour siltation processes were studied: tidal filling and emptying, horizontal eddy circulation in the harbour mouth and density driven vertical circulation. The Harlingen case, with its complex harbour geometry, seemed a promising candidate for a very early pilot application of D-Flow Flexible Mesh, a new hydrodynamic simulation code. Objective of this paper therefore was to investigate its performance, flexibility and efficiency by means of a qualitative comparison with an existing calibrated Delft3D curvilinear model. It was found that the flexible mesh allows for a more precise distribution of high resolution grid cells and capturing of complex geometries using a local triangular network. Moreover, the accuracy of the model was in line with existing Delft3D results. The tide and density driven current were found to be the main contributors to the siltation in Harlingen. Concluding, the applied research method combined with the Flexible Mesh approach look like a promising tool to help identify possible mitigating measures against harbour siltation problems.

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