Programme

Holyhead Breakwater was constructed between 1848 and 1873, creating a Harbour of Refuge which can be accessed during all weather conditions and at all states of the tide. The breakwater currently: provides refuge to cruise ships, ferries, fishing vessels and pleasure craft; provides a well-used recreation space for locals and visitors alike; and reduces the risk of coastal flooding for seafront amenities.

The breakwater is deteriorating and at risk of breaching unless some form of intervention is undertaken in the near future. Royal HaskoningDHV were appointed by Isle of Anglesey County Council (IoACC) and Stena Line Ports Ltd (Stena) to investigate and develop a long-term solution to maintain the Grade II* listed structure as a robust coastal defence for the next 100 years. This paper outlines some of the studies undertaken to develop a viable refurbishment scheme for the breakwater whilst respecting its value as a heritage asset and contribution to Holyhead’s community and sense of place.

‘Catch-up’ is generally understood as a transient period of accelerated shore recession that follows the removal of a ‘hard’ coast protection structure. It can cause significant rapid near-term losses and so should be accounted for when decisions are made about the implementation or discontinuation of protection. Although less well recognised, it has also been associated with the ‘soft’ coast protection approach of beach maintenance. The likelihood of this kind of coastal catch-up occurring along Poole Bay is explored under a counter-factual scenario of cessation of defence maintenance.

This is done through analysis of a shore profile database maintained by BCP Council. The shore of Poole Bay mainly comprises a sand beach over a consolidated platform (or ‘substrate’). The beach is maintained with groynes and periodic beach nourishment. The substrate immediately seaward of the beach is studied and found to be retreating so that the profile is steepening overall. It is concluded that, as a result, coastal catch-up behaviour should be expected if coast protection were to be discontinued. The substrate recession is used to estimate the overall catch-up distance and also the subsequent equilibrium recession rate.

In this paper rock armour and XblocPlus are compared with regard to costs, carbon emissions and the expected maintenance need. A simplified method is presented to predict damage development during a structure lifetime using a Monte Carlo analysis. This MC analysis is based on a limited number of extreme wave conditions with return periods between 1 year and 1,000 years.

Two case studies are presented for which the authors received a design with rock armour and prepared an alternative design with XblocPlus. The maintenance need of the case studies is predicted for two wave climates: 1) the wave climate for 2015 which is seen as current day wave climate and 2) the wave climate that is predicted for the year 2115.

The rock armoured structures have a high probability to need maintenance during their 50 years lifetime and increasing wave heights due to climate change increase this probability. The XblocPlus structures have a low probability to need maintenance and a high resilience against increasing waves due to climate change. For the two case studies the XblocPlus structures perform better than the rock armoured structures with regard to cost and carbon emissions.

Coastal defences can only ever ‘buy time’ in light of future sea level rise. Globally, increasing lengths of the open coast will therefore no longer be able to be defended in the future due to increasing costs and limited benefits in terms of the number of properties protected. This is particularly the case along coastlines that have already been fixed in position for long periods of time; in the case of Southeast England often for more than 150 years.

Moving beaches landwards mimics natural roll-back and is an option to extend the life of beaches to retain some flood defence, habitat, and amenity. Evidence of the benefits of this approach are presented for two sites in Southeast England together with the plans for a more radical approach at a third site based on the growing experience with this approach.

This paper describes using numerical and physical modelling studies to design a Core-Loc and a caisson breakwater for a new port in Rio de Janeiro State, Brazil. The numerical modelling was carried out to examine the difference between the two breakwater alternatives (one is a combined caisson and rubble mound Core-Loc structure, and the other where the whole structure is a Core-Loc armoured rubble mound breakwater) in terms of the wave conditions in the approach channel and turning basin areas.

Wave conditions inside and outside the port have been assessed using a Boussinesq numerical wave model. As part of the design process, the previous consultant undertook a 3D physical model study to determine the wave agitation inside the port and approach channel produced by the predominant wave directions. This excellent opportunity was taken to compare wave conditions between the numerical and physical modelling.

Beach management through nourishment and annual recycling has been applied for over 37 years to manage flood and coastal erosion risk to 1700 properties at Eastoke, Hayling Island, UK. This form of natural flood risk management has proved successful, in avoiding the annual flooding that blighted this area previously. However there have been unexpected storm events which have caused beach erosion and localised flooding.

Using long term real-time nearshore wave datasets and state of the art statistical methods, extreme wave conditions for both unimodal and bi-modal wave events were generated, which have illustrated some concerning patterns. These extreme events have been applied in Shingle-B, a new parametric model, which has indicated a more extreme beach response to bi-modal sea states compared uni-modal (which the beach was originally design for). The model was then applied to sensitivity test alternative beach profile designs.

This has important consequences for frontages like Eastoke, which depend on maintaining a healthy beach crest to avoid erosion and flooding. The Shingle-B results suggest that a beach designed for uni-model conditions may not provide the expected standard of protection for certain bi-modal wave conditions in terms of crest cut back.

The expansion of the Port of Hanstholm, located on the exposed North Sea coast of Denmark has been carried out from 2017-2020. The port expansion features a new large western breakwater in 9-13.5m water depth with 15t to 32.5t Cubipods® as main protective armour. The breakwater head towards the harbour entrance is established by a large prefabricated concrete caisson (40x22x18m).

Detailed design of the breakwater, the largest ever built in Denmark, was carried out by COWI A/S for the marine contractor Per Aarsleff A/S, who won the port expansion design-build contract. This paper presents the design consideration for the new western breakwater, including considerations of different breakwater concepts and details on why Cubipods® in one layer was eventually chosen as the preferred armour for the breakwater.

Groynes are cross shore structures designed to control coastal longshore transport that form significant elements of the coastal protection and flood defence schemes around the UK's coast. Prompted by work to capture good practice in timber groyne management, an updated CIRIA guide has recently been published. Having briefly summarized the content of the guide, the paper goes on to examine in more detail some specific aspects where more significant innovations from research and from practice development have been identified.

These include: timber groyne distribution around the UK; key factors in setting groyne lengths and spacings; designing for, and adapting to, beach profile fluctuations; ensuring the whole life and sustainability of timber groynes; developments in detailing of timber groyne joints and pile abrasion protection systems.

A probabilistic design approach is proposed here for the design of restoration solutions of existing deteriorated rubble mound harbour breakwaters which are no longer able to ensure safety for port operations. The method allows one to consider both the stochastic nature of the variables involved in the wave-structure interaction (i.e. external loads, structure materials and geometry) and the uncertainties related to the imperfect knowledge of the physical laws that govern such a process.

In this context, physical modelling represents a fundamental tool for the definition of site-specific formulations able to describe the response of non-conventional restored breakwaters to wave load, which may be different from the prediction of existing design formulas. The case study of the Catania harbour breakwater was chosen for the implementation of such a method.

After defining an experimental damage progression formula derived from physical model tests on four upgrading options, the probability of failure during lifetime of each configuration was assessed, considering the limit states corresponding to initial damage, intermediate damage, and collapse of the armour layer.

Ocean View Beach is an 11 km length of urban beach located in Norfolk, Virginia, USA, along the southern coast of the Chesapeake Bay. This area has been heavily developed for many decades, so that the sandy beach is backed by a mix of residential structures and commercial structures, hotels, and urban beach parks. The City of Norfolk has also actively managed and monitored the beach system for decades, using sand nourishment and coastal structures (combination of detached breakwaters and groins), including a collective shoreline length of approximately 4.5 km fronted by detached breakwaters (with gaps between breakwater fields).

In this paper, the morphology of the Willoughby Spit vicinity at the western end of Ocean View, several years before and several years after the 2013 construction of seven breakwaters is evaluated in detail. A three-dimensional (3D) coastal sediment transport model (3DCSTM) modelling study used to design a 2020 breakwater field modification is described, including its calibration to observed shoreline and nearshore bathymetry along with multi-year post-construction performance projections.

Typhoon Faxai passed through eastern Japan along with strong winds in 2019. This typhoon destroyed a wide range of seawalls and caused wave-induced inundation in Fukuura and Honmoku in Yokohama. Considering the design method of Japanese parapets against wave pressure has not yet been established, it is important to clarify the factor of damage caused by this typhoon.

In this study, we performed large-scale hydraulic experiments and numerical simulations to examine the mechanism of this disaster. As a result, we found that the wave pressure acted on parapets during this typhoon was unexpectedly larger than the one calculated by the formula normally used for the seawall design because of the configuration of seawalls; parapets was located behind the front of the caisson. This phenomenon could be reproduced by both hydraulic experiments and numerical simulations. We also showed that the wave overtopping from parapets with setbacks from caisson front could be unexpectedly larger than that from parapets in front due to its collapse.

This paper discusses potential ways to enable coastal structures to fully enter the scope of the limit state design promoted by the Eurocodes. After a review of the main basic expressions of limit state conditions, a reminder of the rationale behind the classification into ultimate and serviceability limit states (ULS and SLS) is given, the differentiation of safety levels according to the Consequence Class of the structure is presented, and current practice in hydraulic design is explored.

Focusing on “hydraulic limit states”, the following main findings are presented: (i) Safety level differentiation according to Consequence Class should be allowed for both ULS and SLS; (ii) A direct statistical assessment of the design value of wave/water conditions for use in hydraulic ULS verifications should be developed, in parallel with the factoring of the characteristic value into the conventional structural and geotechnical ULS verifications; (iii) Multiple statistical methods for case-by-case assessments of marine actions and load values should be permitted; and (iv) The Eurocodes partial factors for resistance and criteria for structural and geotechnical limit states, and the formulae in the literature for calculating the stability of rubble-mound breakwaters, should be properly adapted to coastal structures and Eurocodes safety levels.

This paper presents the design process of a coastal protection design in an energetic swell wave climate, consisting of a low-crested breakwater (LCB) structure in combination with a beach nourishment inside a groyne scheme. Hydraulic conditions and morphological stability have been assessed using 1D and 2DH non-hydrostatic XBeach models, calibrated based on 2D physical model testing results. The hydraulic stability and wave transmission of various designs has been assessed using the same 2D physical model testing, resulting in an optimized design of the LCB structure.

The effect of seepage flow on the bearing capacity of the mound for composite breakwater was investigated using a coupled fluid analysis and ground deformation analysis. To examine the validity of the coefficient of resistance from porosity in the previous formula, numerical permeability tests in a U-tube were conducted using a fluid analysis. As a result, seepage flow velocities due to Kadlec and Knight's formula agreed well with Creager's experimental data. Next, the effect of seepage flow on the effective stress at the mound of the breakwater due to the water level difference was examined.

The results showed that the effective stress did not decrease significantly due to a seepage velocity at around 0.01 m/s, while a slight decrease in the effective stress behind the caisson was observed. There are two possible reasons. One is that the seepage velocity is small in this study, and the other is that the acceleration term of the seepage velocity is neglected in our basic equations. However, it has been pointed out that in the u-P form, the acceleration term of the seepage flow is neglected, which causes the calculation to fail when the seepage flow velocity increases.

The British Standard 6349 series covers maritime works with Part 7 addressing breakwater design and construction. The current version of Part 7 was published in 1991 and has recently undergone a major revision with the revised publication due in 2023. The revision of Part 7 moves the maritime works suite of standards closer to being fully ‘Eurocode facing’.

The revised Part 7 will introduce new design approaches, in part based on new approaches proposed in the forthcoming Eurocode on \coastal structures (EN 1991-1-8), expected to be published in 2026. The new approaches represent a significant change in design practise and therefore require clear communication, training, support and (importantly) validation through trial applications.

This paper documents the trial application of the new standard at three sites with distinctly different environmental characteristics: A site on the United Kingdom (UK) Dorset coast benefitting from medium-term nearshore wave measurements in a micro-tidal environment. A site on the UK Somerset coast benefitting from medium-term offshore wave measurements in a macro-tidal environment. A site on the British Virgin Islands (BVI) Atlantic coast without any measured wave data in a micro-tidal cyclone prone environment

The design approaches taken for each site are described with comparisons drawn between deterministic and probabilistic approaches, the prerequisites to allow application of each and the contrasting levels of risk management and optimisation possible. The paper draws conclusions regarding the ease of use of the revised (draft) standard, lessons learned that may lead to changes to the standard before publication, and compare and contrast the differing design routes available based on the perceived level of project risk and supporting data/ methodologies available.

Along the Northern Gulf of Mexico (NGOM) coastline, land loss due to natural and anthropogenic impacts limits the sustainability and resiliency of coastal habitats, which have been further injured by the 2010 Deepwater Horizon (DWH) oil spill. Here we present three case studies for coastal wetland and shoreline restoration projects (“living shorelines”) along the NGOM, each intended to restore DWH affected locations and resources. Balancing restoration goals with coastal hazard risk reduction and other goals requires creative approaches.

Incorporating hard/grey infrastructure (i.e. breakwaters) as shoreline protection features is often necessary to ensure the resiliency of restored habitats. A risk-based approach is employed for each project to optimize shoreline protection feature costs and maximize habitat restoration benefits. The approach has been validated with the performance of the Lightning Point project after construction, when the breakwaters and marsh creation have protected the site from impacts due to eight tropical cyclones.

In general, the caisson-type quay walls can endure surging tsunamis with a good performance thanks to the earth pressure behind the caissons. However, the earth pressure deteriorates the situation by pushing the caissons under the backwash of the tsunamis. This stability depends on the states of the sensitive surroundings of the caissons, and its mechanism has not been comprehended sufficiently.

In order to examine the stability of a caisson-type quay wall against the backwashes of the tsunamis, this study performs hydraulic experiments. And, the effectiveness of the soil solidification and influences of its damage are examined. From the experiments, the solidified backfill enhances the stability of the caisson-type quay wall against overflowing tsunamis even with a damage of the solidified part. Compensating parameters to evaluate overflowing tsunami forces are obtained from the experiments, and the sea-side parameter αr gets stable values as 1.0 < αr <1.0+0.1/h*, while the land-side parameter αf gets various values depending on the models.

The solidified part gains stability and the peak force is reduced by 20% to that without the solidified part. Moreover, if the overflow depth or the sea-side water level gets deeper, the land-side force is reduced more effectively by the solidified part.

Cherbourg (1781-1853) was Europe’s first modern offshore breakwater in exposed tidal waters, initiating an evolution of similar projects around the world. It was born of a perceived military imperative which attracted the necessary state funding, and a willingness on the part of state-sponsored engineers to undertake, and sustain, this unprecedented challenge in a climate of ongoing technical and logistical uncertainty.

The project to create a breakwater at Cherbourg represented a new phase in the C18th arms race; for it to be effective, the speed of completion of the project was the major success criterion, but the task was technically daunting - as the head of the Ponts et Chaussées was forced to admit in 1788, ‘we have been continually obliged to carry forward both works and trials simultaneously’. The operation of these demands created a Catch-22 for engineers; the result was a hugely expensive and chronically inconclusive project, driven by priorities which tended at the outset to ignore, or reject, the existing knowledge bank and thus increase rather than decrease uncertainty.

This paper investigates the green credentials of blended natural armour stone structures, the development of carbon traceability, and reporting and the scope for development of ‘eco’ features within rock armour revetments whilst ensuring engineering fitness for purpose and appropriate design life of such structures.

In the UK, the Environment Agency in partnership with Glasgow University are driving the ‘Greening the Grey’ initiative to promote awareness and uptake on Green Infrastructure and carbon traceability in the built environment. The recent Elmer Sands sea defence scheme is used as a case study to demonstrate sustainable development in natural armour stone sourcing, carbon tracing and biodiverse habitat creation.

The crest level of seawalls is often based on estimates of the amount of wave overtopping. Methods to estimate the mean overtopping discharge have been provided in several guidelines. One of the important parameters affecting wave overtopping is the wind. However, the effects of wind have not been accounted for in detail in present design guidelines although some guidance for coastal structures with crest elements is provided in literature.

For onshore wind the expected wave overtopping discharge at coastal structures with a crest element can be up to a factor 5 larger than for situations without wind. In the present study the maximum influence of wind on wave overtopping at impermeable seawalls with crest elements has been studied based on physical model tests. The result of the study is a guideline to estimate the maximum influence of wind on wave overtopping at seawalls with crest elements.

The Porthcawl Western Breakwater project demonstrates how combining advanced engineering and marine construction techniques with expertise and historical records to repair a complex historic breakwater structure in challenging marine and weather conditions. The 182m structure shelters Sandy Bay from the most extreme wave activity and hence protects hundreds of homes and businesses from the risk of coastal flooding.

Constructed in 1828, the breakwater has stood the test of time, but substantial repairs and strengthening were required to maintain its structural integrity. The structure is at an increasing risk of structural failure due to the increasing intensity of storms and sea level rise due to climate change. There was also a need to increase the resilience of the historic breakwater structure. The form of construction and the condition of the structure varies with modifications and repairs over time. This brought challenges to understanding the nature and extent of the defects and therefore design solutions accordingly.

Innovative investigations were used to inform repairs and design of the solutions required to increase the longevity of the breakwater. A designer, contractor and client team of delivered the solution to improve the long-term resilience of the Western Breakwater.

In response to anthropogenic activities, coupled with sea level rise and extreme weather events, coastal communities are defending their shorelines by constructing breakwaters, seawalls, and other forms of coastal and marine infrastructure. As such, these structures typically support lower species richness and diversity than natural habitats. However, with the addition of slight structural modifications to increase habitat heterogeneity and surface complexity, increased colonization, and enhanced biodiversity of marine species on artificial substrates can be encouraged.

To showcase the ability to apply these ecological design principles to a fully constructive armouring unit ECOncrete® Tech Ltd. designed the COASTALOCKTM. This unit can be incorporated into breakwaters and revetments as an alternative or to complement traditional armour layers, while offering diverse habitats for marine communities, such as water retaining features, overhangs, and cave-like shelter, mimicking natural intertidal habitats that are typically absent along man-made armoured waterfronts. This paper focuses on the drivers behind the structural and ecological design of the innovative armouring units, and the lessons to be learned from the installation within a full-scale pilot project. The results of which support that the design addresses not only the structural and coastal engineering requirements for shoreline stabilization but the awareness of marine habitats when designing any coastal and marine infrastructure.

Overtopping plumes from wave impact is relevant to coastal defence for overtopping analysis of sea walls, levees, and gates. Improved insight into this phenomenon will further enhance the prediction of wave overtopping and its induced hazard, e.g., erosion, saltwater ingress, and a hindrance to traffic. A series of small-scale experiments have been carried out in the WaterLab at TU Delft to characterize the droplets formed by wave impacts.

Focused waves were generated by the piston-type wavemaker to control the wave breaking point on the wall, which allowed the creation of different types of wave impact. Impacts were investigated respectively: non-breaking, flip-through, and air pocket. After the wave impact, all the stages of the plume formation were filmed using a high-speed camera at a frame rate of 500fps. In this study, the spray sheet breakup and droplet formation are investigated. A simple approach to estimate the maximum spray height is proposed, which can be used for the splash type overtopping in the future.

The North Seafront Masterplan of George Town, a UNESCO World Heritage Site, envisioned a much-improved seawall and public promenade along the town’s central Esplanade. The Masterplan foresaw the upgrading of the seawall itself that stretched for about 460m, from the Medan Renong food court to the Royal Malaysian Navy base. The original seawall was not built in one go, but in distinct parts over a period of nearly two centuries, based on necessity and available funds. In the early 19th century, rock revetment and mass gravity walls were the preferred method of erosion control in the face of incessant waves from the North Channel of the Penang Strait.

By late 2017, signs of cavities and holes undermined toe protection. Poorly repaired patches, hastily built to prevent the seawall’s collapse were evident across the entire length of the structure. Various options to protect the structure were explored, with special emphasis on its heritage values and significance within the UNESCO World Heritage Site. Following a thorough muti-disciplinary assessment, a new seawall offset outward from the original footprint of the old wall was constructed.

The initiative was funded by the City Council of Penang (MBPP) and supported by the George Town Conservation and Development Corporation (GTCDC), with the project being jointly supervised by both parties. Following its completion, the project has expanded the city’s limited public space and improved the public amenities along the seafront, receiving overwhelming public response since its opening in May 2022.

Coastal infrastructure is increasing worldwide due to the impacts of climate change and growing populations. There is currently a global drive to create “blue/green” infrastructure in which multifunctional structures are designed to perform their primary function and also provide suitable habitat for marine life. 3D printing technology is an innovative way to produce more complex reef units which can be incorporated into coastal structures to create hybrid multifunctional structures.

The Interreg Atlantic project 3DPARE has designed and printed 3D-printed concrete reef units which test a variety of different habitat features (different sizes of holes, tunnels and overhangs) to determine their attractiveness for marine life. Eight uniquely designed concrete reef units were deployed in the UK, France, Spain and Portugal in Spring/Summer 2020 and have subsequently been monitored to determine their bio-receptivity. After 6 months the reef units have significantly increased the local biodiversity of the sites and there are clear differences recorded between the habitat features.

This pilot study can help inform engineers on the specific features to be incorporated into future subtidal infrastructure to create suitable habitat for marine life and shows that 3D printing provides a convenient method to incorporate these specific features in engineering projects.

Deck structures overhanging rubble mounds are commonly adopted solutions for quay walls for marine terminals in relatively deep water or in geotechnical complex conditions. The interaction of waves with relatively low-lying pile supported decks overhanging wave-absorbing slopes can lead to wave energy amplification and entrapment underneath the deck, which can therefore experience very intense dynamic loading, resulting in significant damage and even structural failure.

A physical model study has been carried out with the aim to explore the relative importance of key parameters and develop new formula for use in the estimation of wave slam forces for design purposes. Different combinations of water level / deck freeboards, wave heights and periods were tested using both regular (monochromatic) and irregular (random) waves. The results showed a relationship between the normalised vertical forces (F*) as a function of the normalised run-up clearance (R*). As expected, once a critical threshold between the freeboard and the run-up has been exceeded, the loads on the underside of the deck start to increase rapidly.

Climate adaptation is a challenge facing coastal communities around the world. Urban waterfronts were invariably developed over centuries and the adaptation of these spaces requires consideration of many competing demands. This paper discusses how the Port of San Francisco located in California, USA has approached the adaptation of 7.5 miles of the San Francisco historic waterfront, the approaches and lessons that have been learned that could be applied elsewhere in the world.

Climate adaptation is a challenge facing coastal communities around the world. Urban waterfronts were invariably developed over centuries and the adaptation of these spaces requires consideration of many competing demands. This paper discusses how the Port of San Francisco located in California, USA has approached the adaptation of 7.5 miles of the San Francisco historic waterfront, the approaches and lessons that have been learned that could be applied elsewhere in the world.

The original “Exposed Jetties Manual” compiled in 2004 by McConnell et al has provided designers and owners of jetties / piers, and related structures with elevated decks, guidance on wave loads on decks and beams since it was published in 2004. That manual developed general guidance on the design of elevated decks subject to wave loadings from site experience, but also included new prediction methods for wave forces on beams and decks based on results from a dedicated series of physical model tests, discussed in 2002 by Tirindelli et al.

Since that manual, further research information has become available, in particular from re analysing the original test data to reduce uncertainty in the predictions, narrow the confidence bands, and reduce corruption by dynamic effects for short duration loadings. The suggested changes to formulae / coefficients were described in 2007 by Cuomo et al. Since then, further data have become available from laboratory tests on wave loads on bridge decks, on vertical walls (Cuomo et al 2010) and on piles (Wienke & Oumeraci, 2005). This paper introduces the new edition of the “Exposed Jetties Manual”, reminding readers of the 1^st edition, and then describing the principal changes for the 2^nd edition.

Keeping the United Kingdom (UK) at the forefront of climate, biodiversity and oceanographic research, the Natural Environmental Research Council and British Antarctic Survey (BAS) Antarctic Infrastructure Modernisation Programme represents the largest Government investment in polar science infrastructure since the 1980s.

The largest BAS research facility, Rothera Research Station (67° 34’ South) supports a range of UK and international collaborative science programmes. A longer, deeper wharf was required to accommodate the new polar research vessel, the RRS Sir David Attenborough (SDA), and replace the existing facility that had surpassed its serviceable life.

Design and construction presented challenges beyond its unique location, warranting an innovative modular structure to be developed. This enabled all fabrication to take place in the UK, limiting site work to assembly and installation.

In the UK £150bn of assets and 4 million people are at risk from coastal flooding, whilst the construction of sea wall defence schemes typically cost at least £10,000/m. With reductions in public funding, rising sea level and 3200 km of coastal defences (i.e. about £3bn), cost savings are required that do not reduce flood resistance.

The design of new coastal schemes and the setting of tolerable hazard thresholds requires site-specific information of wave overtopping, but this information is very rarely available from in situ measurements.

The National Oceanography Centre converted an existing wave measurement technology into a prototype overtopping measurement system "WireWall" to obtain wave-by-wave observations of overtopping velocity and volume. The system was validated against collection tanks in HR Wallingford’s flume and compared with BayonetGPE predictions. Successful trials followed at Crosby, North West England, collecting quantitative data to calibrate/validate: 1) overtopping tools; 2) flood forecasting services; and 3) site-specific safety tolerances.

Multiple WireWall systems have since been deployed at Dawlish and Penzance, South West England, for up to 12 months. Addition of new on-board processing algorithms and telemetry now enables observation-based overtopping hazard to be nowcast (within 15 minutes of detection) via the British Oceanographic Data Centre.

The challenge for the decommissioning of oil and gas rigs around the world is that they are huge, heavy, awkwardly shaped structures that are expensive to tow any distance and require a fairly unique set up in the decommissioning facility in order to dismantle them quickly and safely. However, the energy companies are obliged by law to decommission them and remove them from the seabed at the end of useful life; therefore, there is a growing demand for suitable facilities within relatively close proximity to the oil fields.

This paper describes the challenges faced by the team that worked on the Dales Voe decommissioning base in Shetland that created what is thought to be the highest load bearing capacity quay in the UK at 60 tonnes per square metre; and the deepest of its type in Scotland. The lessons learned from this pioneering experience will help inform the development of other similar facilities.

Following regular disruptions to the Southwest rail network, especially during the storm events of 2014, Arup was appointed by Network Rail (NR) to complete a feasibility review, optioneering and single option development for the Dawlish railway section from Colonnade to Coastguards (C2C) including Dawlish Station and Dawlish Water River basin.

The objective of the project was to assess resilience options to wave overtopping, determine feasibility of each option and analyse their respective advantages to select the most appropriate option. The criteria included resilience performance, sustainability, buildability, programme, adaptation and whole life cost. This paper focuses on wave overtopping as a key driver of the design process with important lessons learned from a large physical modelling campaign.

A staged approach was developed; it involved development of specific criteria for the assessment of the wave overtopping performance; analytical estimations of overtopping performance based on Eurotop, 2018; testing in a 2D physical model to assess the sensitivity to varying seawall configurations; testing of the initial scheme in a 3D physical model; design optimisation in the 3D physical model; tests of the existing/’do nothing’ in 2D or 3D to highlight the benefits of the proposed scheme; development of an adaptive design.

This paper summarises available data from existing case studies on the effectiveness of petrolatum tape to protect steel piles from the effects of corrosion. The paper also compares this data to a site investigation undertaken in 2019, which obtained thickness measurements on a pile wrapping system installed over 30 years ago.

The data has been used to underpin the 35-year life-extension of a safety critical maritime asset (more than 1,000 Circular Hollow Section “CHS” Piles) with expected through life savings on maintenance and inspection. A small number of laboratory tests and site studies on the effectiveness of the petrolatum tape have been undertaken over short periods of time (weeks or months) and the results extrapolated to provide the annual corrosion rate. However, at the time of writing there is no published field data for the long-term corrosion rates of steel CHS piles protected by petrolatum tape.

This paper presents the site data from a UK case study in which piles have been wrapped with petrolatum tape for over 25 years. The site data has then been compared with the published short-term corrosion rate data. When considering the use of the tape system in design or life-extension projects, the corrosion rate can be considered to be a maximum of 0.005mm/year based on a UK site. This assumes that an effective maintenance regime has been implemented to ensure that the tape is not exposed to mechanical damage. Therefore, a petrolatum tape system can be effective at obtaining and extending the design life of marine structures.

The coastal village of Vík is located on the South Coast of Iceland. The area is subjected to the full force of extratropical cyclones of the North Atlantic. The village beach is not a stable phenomenon, after a nearby volcanic eruption in 1918 it accreted by 500 m over 50 years but has eroded since 1970, which poses increased flood risk in the area. Therefore, a study was conducted using a multivariate extreme value modelling to evaluate the current coastal defense structures.

The method in question uses a multivariate joint probability model to simulate variables that cause extreme coastal flooding events. It generates a large sample of extreme ocean events based on a 52-year time series of hindcast data. The large sample of extreme events can then be used to determine return periods for certain events and to determine a desired crest height for coastal defense structures. The study suggests improvements on current coastal defense structures and the design specification for defense structures along a planned road along the coast.

A section of the eastern sea wall at Maîtresse Île in the Les Minquiers archipelago, situated 20km south of the Cannel Island of Jersey and also approximately 20km north from the north coast of France, had suffered several recent collapses in 1978, 2011 and 2018. The archipelago, in an historic agreement of designation between the UK and France in 2016, became under the protection of the UK Dependency Jersey. It is a platform of rock larger than any of the Channel Islands, is larger than say the city of Manchester and several minor European states.

The reef is also one of the Ramsar convention sites protecting migratory birds, is uninhabited, has no power or water and the same 11m tidal range as Jersey itself. Its location is facing directly into the Western Atlantic and the strength of the storms in this part of the Channel and the large area of rocks in the reef makes this a very dangerous location for any sea farers. The rocks are also rich lobster and fishing grounds and have been disputed between French and Jersey fishermen for several hundred years until the agreement of designation to be protected by Jersey.

The publication of the new national Flood and Coastal Erosion Risk (FCERM) Strategy in England sets out a vision of a nation ready for, and resilient to, flooding and coastal change – today, tomorrow and to the year 2100. This ambition needs to be turned into reality for those at risk of flooding and coastal change both now and with a changing climate.

Humber 2100+, a tidal strategy to manage risk against a backdrop of economic growth and development in a sustainable way, is a project leading how we implement that ambition. Humber 2100+ is balancing working in partnership with limited funding to deliver an adaptive pathway to manage flood risk over the coming years, exploring what is necessary for the region to be resilient in a changing climate. Resilience will require a broad spectrum of measures from flood warning and evacuation, through to changes in planning and defence improvements.

In the short-term Humber 2100+ will deliver a substantial programme of investment in both defence improvements and resilience measures to enable the implementation of an adaptive pathway in response to rising sea levels and climate change. We are working with our partners and are seeking to have all the technical work (including consultation) completed by the end of 2023 prior to embarking upon an approval and adoption process.

This paper discusses the use of 2DVertical Computational Fluid Dynamics (2DV-CFD) numerical wave flumes to inform assessments of suffusion risks in permeable structures protecting land reclamation areas. A typical rubble mound breakwater section is presented and key processes during wave interaction with the permeable structure are discussed. Emphasis is given in assessing the influence of the filter layer / geotextile to wave transmission in the breakwater. Results of pressure transmission in the breakwater are presented and compared with empirical methods.

Following the analysis of these processes and CFD model results, recommendations are provided, with respect to best practice and limitations of CFD models for assessing suffusion risks, and for their best use. Recommendations include the use of random waves, to capture the effect of groupiness, recommendations for Darcy-Forchheimer coefficient values (A=150 and B=2 for armour layer and underlayer, use of existing empirical relations for core layer) and the consideration of internal overtopping to estimate water build-up at the landfill. Assessing suffusion risks at the filtering layer with the help of CFD models should be based on estimates of pressure differences rather than calculation of pressure gradients directly from the model.

On the 26th of February 2021, a storm hit the Solent leading an undermined section of the East Wing wall of the Hurst Castle to collapse. An emergency temporary solution was designed, to be constructed in one month, followed in parallel by the design of a permeant coastal protection both having the function to prevent further undermining of the castle and allowing repair works.

The Hurst castle repair works project is an example of a how the design of a coastal structure can change continuously to adapt to variations to budget, materials, construction methods, sequences, time schedule, environmental constrains and many other matters that are not necessarily known at the start of the design phase. A good design is not only one that follows guidelines, analytical calculations and the designers experience, but also one that adapts to the everchanging project requirements and situations while continuing to be a reliable and robust solution.

This paper describes the different design steps which led to the evolution of a temporary repair revetment into a permanent design solution and finally an actual constructed rubble mound. The paper aims to show how a relatively simple design can indeed become complex, when more factors than the purely environmental ones (waves and water levels) come into play. A solution can be found when good communication exists between all involved parties, and problems are tackled one at the time.

Awareness and focus on the climate crisis is increasing, driving the focus on reducing greenhouse gas emissions, particularly carbon, in order to halt, or at least slow down, global warming. The Environment Agency, a non-departmental public body sponsored by the UK Government’s Department for Environment, Food and Rural Affairs (Defra), is responsible for managing flood risk in England. As a leader nationally in environmental and sustainable practices, the Environment Agency has set itself the ambitious target in its emission sustainability strategy to achieve net zero carbon in its activities, including managing flood risk, by 2030 (Reference 1).

Construction is the single largest contributor to the current carbon footprint of the Environment Agency, and thus project teams tasked with delivering flood risk management outcomes have been challenged to seek out opportunities to reduce carbon. This means low carbon designs as well as low carbon materials and methods. This paper explores the feasibility of achieving flood protection in a carbon neutral way, with reference to the annual beach nourishment scheme undertaken on the Lincolnshire coast.

When constructing land reclamations, often sand is placed on top of the coarse rock of the bund surrounding the reclamation. The use of a geometrically open filter between the interface of sand and rock could be cost effective. It is expected that even a geometrically open filter with sand on top of gravel might be stable due to the arching mechanism. For such a “reversed” open filter the actual stability is unknown. Hence this study focusses on the stability of a reversed geometrically open filter under cyclic loading.

This paper mainly describes the development of the test setup.

First the numerical model OpenFOAM was used to extract the gradients from a representative case study. Next a test setup was developed to generate these low-magnitude loads at full-scale. Various sand-filter combinations were tested, with a range of ratios of the diameters of the gravel filter (D15F) and the sandy base layer (D85B) and sand with a unimodal distribution. They were tested for both parallel (i//) and perpendicular (iꞱ) gradients.

The order of magnitude of the occurring gradients obtained with the numerical model for the case-study were a parallel gradient of i//,2% ≈ 1%, decreasing to 0 going downward, and a rather constant perpendicular gradient of iꞱ,2% = 0.2-0.3 for the lowest 4 m of the reversed granular filter. The critical perpendicular gradients were estimated at iꞱc ≈ 0.2 to 0.1 for filter ratios of D85F/D15B = 7.5 to 9.5. The critical parallel gradients were measured at i//c ≈ 2% down to 1%, but might be influenced by simultaneously occurring perpendicular gradients. Even though for the test case no stable situation could be proven with respect to the perpendicular gradient, realistic situations with stable reversed open filters seem possible.

The existing seawall in Georgetown Guyana experiences significant overtopping leading to flooding of the urban area and is, in places, in a poor condition. The existing structure is a 1970’s concrete crest wall and concrete apron on an older embankment. The 7.5 km seawall protects the commercial centre of the city.

There was a limited amount of data available for the design leading to significant uncertainty in all design parameters: no ‘as built’ drawings could be located; local estimates of long-term sea-level rise were not robust; an existing wave study was not intended for use for the design of the seawall; there is no database of ground investigations. Mud waves propagate along the Guyana coast with a period of around a decade and affect the nearshore bathymetry so wave modelling only represents a transient condition.

Design options were considered and assessed for zones along the frontage. The assessment of options considered the sustainable use of materials and the capabilities and practices of local contractors. The chosen options include strengthening and raising the existing crest structures with local raising of the rock revetment. All of the options needed to preserve or enhance the seawall as a recreational community asset. Foundation designs were developed that could be adapted in response to results of localised ground testing during construction.

The UK has set out ambitious targets to achieve net zero on all greenhouse gas emissions by 2050, and as such members of the Flood and Coastal Erosion Risk Management [FCERM] supply chain are responsible for driving a reduction in carbon emissions in response to the 2019 Climate Change Act.

This paper explores the role of the Client within the FCERM infrastructure supply chain in managing carbon. Designers and Suppliers are racing ahead to provide innovative ideas and solutions, but if the Client is not prepared, opportunities to reduce the carbon footprint of these FCERM schemes may be missed entirely. Coastal Partners is preparing to deliver the outline design of an intertidal habitat creation scheme within the Solent on the South Coast of the UK.

The Client has proactively designed the scope of this work to embed principles of carbon reduction from the outset. The Designer’s scope is to include investigations to identify a sustainable and viable solution that is not only value for money, our society and the environment, but now also best for carbon. Whilst it is recognised this project is still in the early stages of the supply chain, the message is clear that the Client has an urgent role in realising opportunities for carbon management at the conception of FCERM infrastructure projects, and that it is necessary to show leadership throughout the supply chain process to ensure that targets are met alongside the delivery of the scheme.

Once the scheme is delivered, it will be too late. This paper aims to inspire other Clients entering the supply chain for delivery of FCERM projects between now and 2050 through demonstration of simple steps that can be taken to set up a sustainable supply chain for collaboration and innovation in carbon reduction to net zero by 2050.

At the Shinmoji-Oki disposal pond (S-3 area), as one measure to expand the acceptable capacity of dredged material, the revetment has been raised by using mechanically dewatered clay (MDC) lumps which is made of forcibly dewatered dredged clay and compacted. In general, hill-cut material soil is used as the material for revetments; MDC was used for the first time in Japan. Since MDC is an artificial material, its long-term characteristics should be confirmed.

Therefore, an incremental-loading consolidation test has been conducted since 2011 when the extra-fill of revetment was constructed. Furthermore, a direct shear test has been conducted last year and it has been confirmed that the failure criterion used in the design of revetment is valid. In this paper, we described the results of its geotechnical properties through these tests and verify its stability for 10 years.

In the New Safi Port Project, which was constructed in the Moroccan city of Safi on North Africa’s Atlantic west coast; Antifer blocks were used as the main breakwater armour layer. The location of the project, which was exposed to rough sea conditions resulting from the major Atlantic swells. Due to a very tight work schedule the project team had to focus on an alternative placement technique for the Antifer blocks rather than the conventional methods of using divers.

It was decided to use the Echoscope® system to overcome poor visibility and improve productivity. A unique hydraulic lifting apparatus and frame was designed by the project engineering department to adapt this sonar imaging system to the cranes. The system gave a 3D view underwater in real time and allowed the crane operator to place the blocks. Consequently, the operation continued 24 hours a day, independent of the underwater visibility, and in most sea conditions.

In a short while, the daily installation rate improved from maximum 20 blocks per crane, to over 90 blocks per day. This was the first time, the Echoscope®, hydraulic lifting apparatus, was used for the placement of Antifer blocks in a tidal Atlantic coast port project.

The Bacton Sandscaping scheme is a large-scale beach nourishment, designed to protect the Bacton Gas Terminal from coastal erosion while also reducing flood and erosion risk to the neighbouring communities of Bacton and Walcott, buying the time they need for adaptation to coastal change. The scheme was inspired by the Dutch Zandmotor project, designed to work with natural processes and achieve multiple benefits.

The scheme was implemented in 2019. Since then, the beach has changed shape and size in response to storms and daily tides, closely observed by an extensive programme of monitoring and analysis, including development of a Digital Beach Twin. The programme included innovative monitoring techniques to produce a complete Digital Terrain Model, with no gap between topography and bathymetry data.

The analysis identified and tracked the emergence of a nearshore bar and beach scarp, assessed changes in volume and shape of the beach, estimated longshore transport and attempted a volume balance. It also reviewed the design prediction of 15-20 years functional life. The main conclusion is that the scheme is behaving broadly in line with the design predictions, in terms of alongshore interaction and scheme life.

With sea level rise and the potential impacts of climate change, wave overtopping of seawalls around the UK is of increasing concern and importance. This paper briefly describes the current information available to designers and engineers for predicting overtopping discharge of vertical or steeply sloping structures. Three physical model experimental studies undertaken for Arup are described and the measured discharges used to investigate the influence of the different structural elements.

The majority of the elements reduced mean overtopping discharge compared to a simple vertical wall. A set-back wall, even a small one, was the most effective element. The three studies also highlight the value of physical modelling in accurately quantifying the overtopping for the different structure configurations, particularly for more complex structures.

Concrete armour unit single layer breakwater control with 3D digital twin SEABIM® is a patented shape recognition process to create an as-built 3D model of a concrete armour unit breakwater, using a high-density point cloud as input. The resulting model constitutes a digital twin of the breakwater, that enables to check for singularities during the construction or to plan for maintenance operations. Indeed, the 3D model allows for an objective analysis of the interlocking of the blocks, especially around the hidden faces which are hard to control in video inspections or in a point cloud.

The model can be stored and compared with other models created at further dates, to follow the evolution of the structure in the asset management phase. It can be shared amongst the stakeholders of a project and facilitate the handover after construction. The breakwater construction should follow precise installation rules.

Working with experts in breakwater certification, a set of tools has been implemented to check those criteria automatically in the 3D model, like the packing density, the off-profile blocks, neighbouring blocks placed in column or with similar orientations, and holes in the armour where rocks from the underlayer could pass through. The process has been generalized to the most common types of units and has already been validated on several large-scale projects.

At Sabah Al Ahmad Sea City, Kuwait; the extension of an existing shore-aligned promontory to provide high value residential development with a high-quality amenity beach environment. The tightly curved end of the promontory, exposed to waves, tides and currents, created a particular challenge. This paper describes the engineering process and optioneering undertaken to enable the construction of beaches within this environment, with specific application of the static equilibrium bay method developed by Hsu et. al. It comments on the challenges of using this tool for beaches exposed to highly oblique wave attack and presents a slight modification to the Hsu et. al. method to account for divergences experienced. The concluding section provides a commentary on the construction methodology adopted for the promontory and initial feedback on the performance of the design validated through satellite imagery and site survey.

This paper contains two topics: stability of a pitched rock slope (in contrast to randomly placed rock) and mitigation of excessive wave overtopping at an existing rock slope. The stability of a single pitched rock layer could reasonable well be predicted by the Van der Meer formula. The criteria for start of damage and failure, however, become much stricter for a single armour layer. The commonly used EurOtop-equations for wave overtopping were used to fit influence factors for a vertical wall, with and without bullnose, and for a wave return wall.

A vertical wall will increase the crest level, where the wave return wall, replaces a part of the crest of the rock structure and has the same crest level as the original structure. Test conditions were focused on steep waves (high wave steepness) only, as this is the actual design situation for Singapore structures facing the sea directly.

The Cowes Outer Harbour Project (COHP) comprises a 300m long breakwater across the entrance of the Medina Estuary. The breakwater has turned the Medina Estuary into a sheltered harbour thus allowing the expansion of permanent and temporary berthing facilities in Cowes. The breakwater was constructed between 2015 and 2017 and is unusual because over most of its length the ground conditions comprised soft and compressible clays of up to 19m in depth. These challenging conditions required carefully planning and collection of soils information and the selection of a suitable construction method.

The form of construction chosen was a low crested rubble mound breakwater. This was designed to reduce wave transmission into the harbour so that good berthing conditions could be achieved. The foundation included the consolidation of the underlaying soft soils through preloading, which was accelerated by using installed plastic vertical drains and a sand blanket. The design analysis determined that a high strength geotextile reinforcement was also required to achieve global stability particularly for the construction phase. At the end of the defects period in 2017 it was expected that the residual settlement would be no more than 0.3m over the remaining design life.

ABSTRACT Interest in applying nature-based and living shoreline solutions is increasing globally, and the benefits of these multifunctional approaches to managing shorelines are well documented. However, the application of coastal engineering design methods to develop structures suitable for the development of habitats is still evolving. This paper presents the approach adopted in the design of 33 low-crested breakwaters for the restoration of oyster reef habitat at a north Florida Gulf Coast project site in the Pensacola Bay System.

This paper presents a new set of physical model tests on wave propagation over complex coastal bathymetry and wave overtopping. These relate to a coastal defence with a steep front wall and a setback wall. The experimental measurements are reproduced numerically using the SWASH model. Experimental measurements are also compared to state-of-the-art numerical and analytical methods of predicting wave overtopping (Artificial Neural Networks, EurOtop equations). Considerable discrepancies between experiments and predictions are observed.

These are resolved using a newly proposed method, which adapts theoretical predictions to measurements. Finally, this method is verified against additional experimental data and is shown to provide an effective way to define adaptations to existing infrastructure to satisfy engineering design criteria.

The unconventional inclusion of monolithic vertical type structures besides traditional rubble mounds in shallow water yacht harbours can pose interesting challenges for both design and construction. This paper describes the problems and solutions of two recent microtidal projects in western Italy, located at the mouth of the river Arno (Boccadarno at Marina di Pisa) and of the drainage channel Rio Martino (Latina, near Rome). The vertical structures made with either r.c.caissons or a crown of micropiles improve the stability, the navigational safety, the wave attenuation and the siltation problems.

This paper presents a case study into the Eko Atlantic City development in Lagos, Nigeria. It describes the planning, design and construction of the development and explains how the project, in combination with the repairs to the Lagos Moles (breakwaters), has provided a solution to the long-term erosion of Bar Beach which fronts Victoria Island.

Following extensive damage associated with a major (Category 5) hurricane which made landfall in the northern Gulf of Mexico coastline in 2018, Tyndall Air Force Base (AFB) is currently being rebuilt to achieve higher levels of resilience to high wind and flooding, whilst also being environmentally and socially sustainable.

Alongside the rebuilding work, a range of studies have been carried out to investigate how the USAF mission activities at Tyndall can be protected from coastal flooding into the future i.e. how the resilience of the AFB can be provided in the face of rising sea levels and hurricane activity. This paper summarises the work that has been done to build coastal resilience at Tyndall AFB and explains how nature-based solutions (NBS) have been considered. Key aspects of the work include the development of pilot projects, stakeholder engagements and the development of a long-term strategic plan.