Coastal Structures and Solutions to Coastal Disasters 2015: Resilient Coastal Communities

In 1931 a major earthquake altered elevations along the shores of Hawke’s Bay, raised by 2 m at the north end of the study area, decreasing alongshore with 1-m subsidence at the south end. While the uplifted gravel beaches created stable barrier ridges, now developed with homes, concerns are that with projected accelerated rates of rising sea levels and increasing storm wave heights, erosion and overwash impacts will return. Analyses have been undertaken of the measured tides, waves, and calculated swash runup levels on the beaches, combined to yield a record of hourly total water levels at the shore. Its extremes are compared with the elevations of surveyed beaches and gravel ridges, to project future property hazards. In that little more than a decade of measured waves were available for our analyses, the morphologies of the ridges provided evidence for past more extreme storm events and water levels, which had occurred in the 8 decades since the earthquake, and land-elevation changes.

Sediment discharge from the rivermouth is very important to conduct numerical simulations of coastal sediment transport in order to propose and evaluate wide area countermeasures of beach erosion. However, the measuring method of suspended load transport rate and bedload transport rate of the river has not been established yet. Therefore, in this study, the measuring method of river sediment discharge was established by using the turbidity meter and ADCP and numerical simulations of coastal sediment transport were conducted by applying observation results to boundary conditions in order to clear the sediment behavior of the Kashima-Nada Coast in Japan.

Folly Beach County Park (FBCP) is situated along ~1,000 meters (m) or ~3,300 feet (ft) of shoreline at the southwestern end of Folly Beach near Charleston, South Carolina, U.S.A. Net sand transport is east to west with the adjacent inlet tending to draw sand from the oceanfront. Nourishment in the form of navigation channel disposal and a 50-year federal shore protection project helped maintain the unstabilized spit at FBCP for many years. However, lack of beach fills after 2005 resulted in dune line recession of over 36 m (~120 ft) in five years, loss of parking facilities, and exposure of underlying marsh sediments along the oceanfront. The authors were retained by the Charleston County Park and Recreation Commission (CCPRC) to evaluate the erosion and outline alternatives for restoration. A total of 317,300 m³ (415,000 cubic yards) nourishment and a 225-m (745-ft) steel sheet pile groin with a concrete cap and armor stone toe protection were determined as the optimal means of restoring and maintaining a recreational beach and protecting park infrastructure. The groin at FBCP was designed to follow the local beach profile to the extent practicable in order to reduce the exposure of the structure. It was composed of three sections: berm, beach face, and low-tide terrace. The berm section served to hold the major dry-beach fillet on the updrift side and a minor fillet on the downdrift side, and the beach-face section followed the average slope of the beach across the intertidal wave swash zone. The low-tide terrace section stabilized the profile above the low watermark, and a scour apron of quarry stone was designed at the seaward end of this section for toe protection. Beach nourishment started on 5 May 2013 and finished in 20 days on 24 May. The groin construction was completed over 35 days between 15 May and 19 June 2013. The project was completed on time and without any environmental incident. FBCP re-opened on 3 July 2013 and remains a premier recreational destination in the Charleston area. The American Shore and Beach Preservation Association (ASBPA) announced in May 2015 that the FBCP project is a winner of its 2015 Best Restored Beach award for its successful enhancement of storm protection, habitat restoration, and recreation restoration.

According to recent issued IPCC 5th Assessment Report (AR5), sea level will rise and wave characteristics will change in future climate with very likely. Shoreline and morphological change has been concerned under the effect of those climate change. In this study, a numerical model of beach profile change which can take into account of the effects of changes of sea level and wave conditions as forcing factors was applied in order to investigate the shoreline and contour line change of sea bottom at Kaike Coast in Japan from present to future climate.

Winthrop Beach faces the open ocean, is approximately 7,000 feet in length, and is situated along the east side of Winthrop between two glacial headlands or relic drumlins. To address the issues of shore protection and “sediment starvation” along the Winthrop Beach shoreline, a beach nourishment project has been designed to return the shoreline to historic conditions. Unlike most beach nourishment projects in the United States, the material proposed for restoration of Winthrop Beach consists of mixed cobble, gravel, and sand sediments. Due to the origin of the native beach (erosion of glacial drumlin deposits), the in situ beach material consists of poorly sorted materials ranging from fine sand to cobble. The total beach fill length was approximately 4,200 linear feet and the equilibrated berm width is designed at 100 feet. The total nourishment volume was approximately 460,000 cubic yards. Once the beach nourishment was completed in late 2014, the high tide shoreline was pushed more than 150 feet from the seawall, with a gradual slope extending approximately 350 feet offshore. Although shoreline change modeling indicated a design life of approximately 10 years, it is anticipated that the coarse fraction of the nourishment material will be naturally sorted by wave action and form a gravel/cobble berm along the upper portion of the beach (observed along the natural mixed sediment beaches of the New England coast). Initial monitoring results after the first complete year post-nourishment support this finding, as minimal sediment loss has occurred, despite an active nor’easter season in the winter of 2014-2015.

The general longshore transport (GLT) model represents a practical tool for the estimation of longshore transport (LT) for a large range of conditions, from sandy beaches till reshaping breakwaters. The GLT model is based on an energy flux approach combined with an empirical relationship between the wave induced forcing and the number of moving elements. In the present paper, the suitability of the GLT model is assessed by means of the comparison between the LT predictions and the observations from different data sets covering a wide mobility range of the units: from stones to sands.

A cross-shore shoreline change model has been applied to the New Jersey coastline to provide predictions of regional shoreline position on timescales ranging from short-duration storm events to longer term seasonal fluctuations. The model relies on environmental input from readily available sources such as wave buoys and water level gauges, and is based on conservation of volume arguments and equilibrium beach profile theory. The model responds exponentially with time to variances in the equilibrium shoreline position, and the rate at which the shoreline approaches equilibrium is determined by a coefficient that is modified based on whether the profile is accreting or eroding. Eight parameterizations of the rate coefficient were investigated, as well as various methods for predicting erosion vs. accretion. The coefficients were calibrated to shoreline position data collected in Mantoloking, NJ. The study results show that the model can be used to predict shoreline position with a minimum mean absolute error of 3.53 m and a maximum correlation coefficient of 0.8104.

Core-enhanced sand dunes are hybrid coastal defence structures that combine the storm surge protection offered by traditional hard coastal structures with the aesthetically pleasing appearance and wave energy dissipation potential of coastal sand dunes. Essentially, these are hard coastal structures covered under a sacrificial sand dune. In this study, ongoing conceptual design efforts of such structures for a potential Houston-Galveston region storm surge suppression system are presented along with results from physical model tests of three different core-enhanced dunes. These tests were carried out in a moveable-bed wave flume to determine the erosion evolution and technical feasibility of various core-enhanced dunes under irregular wave attack. Results were compared to a plain sand dune without core-enhancement. The three different cores under investigation were a clay levee, an armour stone revetment, and a T-wall. Findings showed that profile evolution of the core-enhanced dunes varied significantly based on core structure.

Hurricane Sandy destroyed coastal areas along the Atlantic Coast of the U.S.A. upon making landfall on 29 October 2012. High storm surge and waves caused severe overwash and breaching on both uninhabited and developed barrier islands. In this study, we evaluate the extent to which erosion is affected by infrastructure using the numerical model XBeach. Several scenarios are simulated to represent Mantoloking and Bay Head, which are neighboring townships on an urbanized New Jersey barrier island: the ‘developed’ scenarios include buildings and a buried seawall as they existed in their pre-storm conditions, and the ‘abandoned’ scenarios exclude the buildings and the seawall. Comparing these scenarios, we determine the seawall greatly reduces erosion on the dune and landward side, but erosion is exacerbated by buildings due to flow channelization. When both buildings and the seawall are removed, the barrier island is completely inundated and overwashed into the bay, indicating a landward migration of the island. These results show coastal infrastructure can have extreme effects on barrier island response to storm events.

This paper investigates the damage caused by three different mechanisms-wave impact, scour/high velocity flow (HVF), and debris impact-to the oceanfront structures of two New Jersey coastal communities during Hurricane Sandy. The two neighboring communities, Bay Head and Mantoloking had similar dune sizes and beach profiles before the storm, with one major difference: buried within the dune line along most of the length of Bay Head, was a relic rock seawall. The research compares the effects of the two different shoreline protection systems employed by each town, and finds that: (1) areas with the rock seawall experienced less erosion behind it but more erosion seaward of it, when compared to sections of shoreline without the rock seawall; (2) for structures with the rock seawall protection, wave impact and scour/HVF predominantly resulted in minor damage, whereas for structures without the rock seawall protection, wave impact and scour/HVF predominantly resulted in severe damage; and (3) the variation in distance to the 0 ft NAVD88 contour caused greater variance in damage levels of wave impact and scour/HVF than the variance in beach protection type.

Nature-based solutions to storm protection, such as sand dune restoration and construction, are a flourishing topic in coastal engineering. A crucial aspect of developing nature-based mitigation techniques is evaluating the efficacy of these approaches (i.e., evaluating their economic value) to justify the cost of investment. The objective of this study was to develop a methodology to quantify the monetary storm mitigation value for the dune systems of the Texas Coast during Hurricane Ike. The basic approach for the analysis was to parameterize the pre-storm dune size for different sections of coastline. Then, a regression analysis was used to determine if dune size was correlated with reduced landward home damage. The dune parameters of vegetation area and sediment volume were both significantly correlated with reduced landward home damage at a total value in excess of six million U.S. dollars across the ~18 km of shoreline analyzed. This developed methodology provides the first quantitative estimate of the protective value of dune systems based off storm-induced property damage data, but continued research is needed to improve this methodology and build on this topic.

Primary frontal dunes at sandy shores are essential features to mitigate flooding and erosion damage to coastal properties and infrastructure by coastal storms. Projecting the geomorphologic response of the beach and dune profile caused by extreme storms is required to establish risk levels to upland improvements. Procedures are available to predict dune erosion, and detailed examination of their performance would be valuable in selecting the appropriate tool for given storm and beach characteristics. Two geometric models (the Kriebel and Dean Method; the McDougal, Komar, and MacArthur method), one analytical model (the Larson, Erikson, and Hanson wave impact model), and two process-based models (SBEACH and XBeach) were applied with data for known storms to surveyed beach and dune profiles along a 10.6 km (6.6 mile) reach of shoreline south of the Grays Harbor Entrance in Washington State. To compare performance of these methods in predicting beach and dune changes in severe storms, locations were selected within this reach that demonstrate a range of morphologies and local sediment budgets. Results of applying the dune erosion models illustrate the predictive accuracy of the geometric models, for which few input adjustments are available, and the range of adjustments that are required for the process-based models to optimally represent measured beach and dune modifications. This paper presents pre- and post-storm profiles of the beach and dune at both accreting and non-accreting locations, details of the storm waves and water levels bracketed by the surveys, and an evaluation of the models’ predictive capabilities.

There is considerable interest in understanding the hydrodynamic and geomorphic response of coastlines to sea level rise (SLR). Various researchers have investigated the nature of these changes in storm surge-dominated environments; however, fewer studies have investigated the response of wave runup-dominated coastlines. This paper develops a conceptual model of total water level (TWL) response to SLR and shoreline change for a variety of shoretypes. The conceptual model was developed through analytical techniques and application of a 1-D transect-based TWL analysis, taking into account the effects of SLR and shoreline change. The results indicate that dynamic shoretypes such as sandy beaches, dunes, and erodible bluffs may experience a linear increase in TWL in response to SLR and shoreline change, while static shoretypes such as resistant rocky cliffs and coastal structures may exhibit a non-linear increase in TWL. The study findings can be used to communicate the implications of implementing various physical adaptation strategies to reduce exposure to coastal hazards and to inform better decision making in the face of changing coastal conditions due to climate change.

The vision for STORMTOOLS is to provide access a suite of coastal planning tools (numerical models, etc.), available as a web service, that allows wide spread accessibly and applicability at high resolution for user selected coastal areas of interest. The first tool developed under this framework was a simplified flood inundation model, with and without sea level rise, for varying return periods. The methodology is based on using the water level vs return periods at a primary NOAA water level gauging station and then spatially scaling these values to generate a map. The spatial scaling was performed using predictions of high resolution storm simulations performed by NOAA using their sea, lake, and overland surges from hurricanes (SLOSH) model for various hurricane categories and by the U.S. Army Corps of Engineers (USACE) ADCIRC/WAM/STWAVE numerical hydrodynamic/wave model predictions performed as part of the north atlantic coast comprehensive study (NACCS) for synthetic tropical storms, to estimate inundation levels for varying return periods for coastal waters. The mapping methodology follows the NOAA sea level rise protocol and is applicable to any coastal region. The scaling for the RI application used Newport, RI, water levels as the reference point. The predicted flooding based on NACCS model predictions were comparable and within the range of uncertainty to that based on the SLOSH-NOAA based method. Predictions are provided for once in 25, 50, and 100 yr return periods (at the upper 95% confidence level), with sea level rises of 1, 2, 3, and 5 ft. Simulations were also performed for historical hurricane events including: 1938, Carol (1954), Bob (1991), and Sandy (2012) and nuisance flooding events with return periods of 1, 3, 5, and 10 yr. The maps are web accessible via ArcGIS and being widely used in municipal and state wide planning ().

The old city center of Gothenburg is constructed as a fortified city in a former marsh at the mouth of the river Göta älv in 1619. The present city expanded around the old city on low laying grounds located just a couple of meters above sea level. The city is now flood prone due to the position of the city. The city has experienced floods several times during the last 10 years. The frequencies of floods will increase due to the expected sea level rise. Storm surge barriers and levee reinforcement are needed in order to prevent the city from flooding. This paper gives an overview of storm surge barrier strategies, the storm surge barrier master planning methodology, a systematic design methodology based on systems engineering, and adaptive delta management principles applied for the Gothenburg case. The methodologies are used in order to assess the flood related problems of the city and the development of a safe protection strategy.

In 2010, a report, Mapping the Zone, Improving Map Accuracy, was prepared by a FEMA flood map committee appointed by the National Academies’ Water Sciences and Technology Board, which discussed theoretical and practical issues related to FEMA map accuracy. The present analysis presents a case study, which addresses in particular one of their major concerns: the use of a 1-D model to solve a 2-D problem. Finding #2 in the report stated: “Coastal flood maps can be improved significantly through use of coupled two-dimensional storm surge and wave models and improved process models, which would yield more accurate base flood elevations”. The study re-computes the 100-year inundation maps in Washington County, using two-dimensional models. The initial and boundary conditions for wave simulations are based on results of fully coupled 2-D surge and wave models, the advanced circuulation model (ADCIRC) and the phase-averaged steady state spectral wave model (STWAVE), respectively, from the North Atlantic Coast Comprehensive Study (NACCS) performed by the U.S. Army Corps of Engineers. Waves are simulated using STWAVE over a series of high-resolution grids in nearshore and overland areas. Results are mapped and compared with FEMA’s maps and transects.

In 2008, Hurricane Ike made landfall over the Bolivar Peninsula in Texas. Most buildings were single-family residences, elevated on piling foundations. Several thousand houses were destroyed. This paper examines the importance of the elevation of building foundation components relative to the maximum wave elevations on the survival or failure of the building. Storm surge/wave gage measurements are compared to Federal Emergency Management Agency (FEMA) flood insurance rate maps and several Ike-specific storm-surge models. The best accurately predicted the observations near the Gulf. All of the models significantly over-estimated wave conditions on the landward side of the peninsula. Near the Gulf, elevated building failures were initiated when maximum wave-crest elevations reached the bottom of the floor joists, with near 100% failures 1.2 m (4 ft) higher. Farther from the Gulf, failures occurred over a lower, wider range. Most building failures occurred within 678 m (2225 ft) of the Gulf, although more inland buildings were deeply flooded without apparent wave damage.

The Coast Guard (CG) has established a successful post disaster infrastructure evaluation process that results in immediate site remediation and damage control, as well as development of future restoration projects. Following a natural disaster, the CG immediately deploys a damage assessment team (DAT) to investigate storm damage and give instructions to a repair team who will take immediate corrective action. The CG’s approach can be replicated and used on facility damage sustained by natural disasters, of any scale. Organizations with multiple facilities can have a small designated assessment team trained to look for specific hazards utilizing a standardized checklist. The importance of a quick response prevents further damage, saves money, and increases the lifespan of that facility. This paper will discuss the CG’s approach to immediate assessment and repair of facilities following natural disasters. The two case studies demonstrate implementation of this process on varying degrees of post disaster destruction.

Above ground storage tanks (ASTs) are thin walled structures that often store hazardous substances. In the United States, a large number of these ASTs are situated near the coast, such as the 4200 tanks in the Houston Ship Channel. Proximity to the coast makes these tanks vulnerable to the multiple threats posed by hurricanes, such as wind and storm surge. During hurricanes Katrina and Rita, several AST failures were reported leading to spillage of over seven million gallons of petrochemical substances. Such spills have catastrophic impact on the surrounding environment and habitat. Reconnaissance reports identify floatation and wind buckling of ASTs as the primary modes of failure. Since floatation failure of ASTs may cause catastrophic spills, one of the solutions is to anchor the tanks to their foundations. This solution may prevent floatation of tanks; however, a recent study, by the authors, suggests that large external hydrostatic pressure due to storm surge may buckle the thin shells of ASTs containing a low level of produce. Buckling of the tank shell may cause delays in resuming operations of facilities and may even rupture the shell leading to a spill. In order to prevent such failures, this study aims to assess the effect of stiffener rings, which are known to be effective in preventing wind buckling but have yet to be evaluated for their potential to mitigate surge buckling probability. For this purpose, surge buckling fragility of a representative tank from the Houston Ship Channel will be evaluated with and without stiffener rings. Such fragility models depict the conditional probability of buckling given surge and internal liquid level. In order to derive the fragilities, buckling simulations in the finite element software package LS-DYNA will be conducted across a range of surge elevations and internal liquid levels, while propagating uncertainty in other modeling parameters. The results of this study aid in assessing a potential surge buckling mitigation strategy which may prevent catastrophic spills and reduce delays in resuming operations in industrial facilities after hurricanes. Future work will evaluate the surge risk to a portfolio of tanks and explore the application of stiffener rings along with other structural and regional protective strategies for mitigating risks across the region.

The objective of this paper is to present the results of a study on the effects of storm surge and sea level rise on the coastal town of Wickford, Rhode Island, and an evaluation of possible mitigation strategies. The analysis included estimating the 100 year still water elevation for Wickford, recreating FEMA’s FIRMs using the Coastal Hazard Analysis Modeling Program, and using a simplified surge model to evaluate flooding from different scenarios of storm surge associated with a given return period and varying amounts of sea level rise. The use of vertical barriers placed at key locations was evaluated and illustrated effectively both the reduction in flooded areas and the limitations of the mitigation strategies.

The objective of this undergraduate research project was to evaluate the Federal Emergency Management Agency’s (FEMA) methods for estimating wave heights, wave crests, and wave loads on residential buildings in coastal flood zones. Laboratory scale model tests were conducted in the United States Naval Academy’s Coastal Engineering Wave Basin to measure the characteristics and forces imposed by shallow water breaking waves on elevated wall panels. Tests revealed that FEMA underpredicts wave height, wave crest elevation, and lateral wave slam forces. This paper details these research efforts, including background information, laboratory setup and procedures, and the analysis. In examining FEMA’s guidelines, this paper suggests that FEMA should re-evaluate coastal construction regulations to reduce the effects of wave slam on buildings during storm conditions.

St. George Island is one of the Pribilof Islands of the State of Alaska located in the Bering Sea. The small island has a single harbor that provides the community’s primary opportunity for generating revenue through the thriving local fishery as well as the only mode of delivering critical supplies and fuel to the remote locale. However, large breaking waves at the harbor entrance and significant oscillations within the harbor create unsafe conditions for harbor users. The Alaska Department of Transportation & Public Facilities (DOT&PF) and HDR Inc. (HDR) are designing improvements to provide a safer, more functional harbor. The small size of the harbor, extreme wave conditions, and high cost of construction in this remote and hazardous location present significant design challenges. BOUSSINESQ wave modeling using BOUSS-2D and FUNWAVE was employed to simulate waves approaching and entering the harbor, capturing wave shoaling and breaking, diffraction and refraction past the harbor structures, and infra-gravity waves within the harbor. These models were applied to analyze both the existing and proposed harbor configurations.

The Coastal Hazards System (CHS) is a coastal storm response data resource. The focus of the product is distribution of regional coastal high-fidelity climatological and hydrodynamic modeling results and associated measurements including storm wind, atmospheric pressure, wave, surge, water level, currents, tropical cyclone parameters, statistics of the above processes, and any other pertinent data. The data files include peaks and time series. Tropical storm parameter time series include latitude and longitude of center, minimum central pressure, central pressure deficit, radius of maximum winds, wind speed, forward speed, heading, and land-falling location. Joint wave and water level statistics are provided. A primary CHS goal is to offer storm responses that span practical probabilities with average return intervals of 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 2000, 5000, 10000 years provided. Epistemic uncertainties in the form of upper confidence limits of 84%, 90%, 95%, and 98% are also provided. Finally, relative probabilities are provided for tropical storms to allow sampling of storms in a life-cycle analysis. This information is generated within regional studies such as the FEMA Risk MAP program and USACE North Atlantic Coast Comprehensive Study. The high fidelity modeling conducted within these studies is produced in a statistical context that is useful for federal, state, and local coastal engineering and risk assessment projects. The comprehensive nature of these studies combined with the high level of computational and statistical analyses is a relatively recent development and the CHS is designed to make consumption of these data relatively simple in order to support probabilistic engineering and science studies.

The present study aims at the development of after-runner storm surge (ARS) forecast model using an artificial neural network in Sakai Minato and Hamada on the Tottori Coast, Japan, that is made in 30 hours in advance. To develop an artificial neural network-based ARS forecast model, local meteorological and hydrodynamic parameters (surge level, sea-level pressure, depression rate of sea-level pressure and typhoon location of longitude and latitude) on the Tottori Coast are collected. A series of experiments is carried out to improve the ARS forecast model as varying the unit number from 13 to 130. As a result, it was found that the accuracy of ARS forecast model is improved as increasing the unit number. Then, we can obtain the best performance of the ARS forecast model with the given lead time. In addition, the optimal unit number for the given lead time can be determined.

Exposed on three sides to the Gulf of Alaska, the Cook Inlet region is an extremely dynamic system which has among the largest waves in the world. In addition, Cook Inlet exhibits the largest tidal fluctuations in the United States, and as a result, the nearshore regions encounter significant flooding and drying which poses threats to a variety of activities in the coastal regions. A coupled wind-wave-current system is developed to obtain daily forecasts of waves and circulation patterns. The SWAN wave model and the quasi three-dimensional EFDC flow model are implemented, using high-resolution WRF winds. The performance of these models is first verified using hindcast simulations. The forecasting system also simulates the extent of “wet” and “dry” regions in the coastal areas. The nested grid approach is utilized with high-resolution grids for two separate regions, namely the Kachemak Bay (KB) and the Upper Cook Inlet (UCI) region. To validate the efficiency of the forecasting system to reliably predict the wave parameters, satellite data from currently flying missions such as JASON-2, and CRYOSAT-2 are utilized. Moreover, the data from the Terra (MODIS) satellite are used to obtain true color and land reflectance (band 1-2) images of the Cook Inlet region. These images are then used to corroborate the efficacy of the system for providing accurate estimates of the extent of “wet” and “dry” regions. Good agreement between data and model results demonstrate the efficiency of this coupled system for operational forecasting.

The Grays Harbor federal navigation project is on the southwest coast in Washington State, U.S.A. Recently, increased wave energy associated with the morphology of the harbor inlet throat has resulted in significant damages to the Point Chehalis revetment. Nearshore wave heights at the revetment have increased to the point where wave overtopping occurs routinely during a typical storm season (late October to late March). The high frequency of overtopping has resulted in progressive damage and subsidence of the structure over the past decade resulting in emergency repairs in 2010. This paper presents risk management tools utilized to help predict where future damages would occur as a result of the evolving nearshore wave conditions as well as a rehabilitation plan to mitigate future damages over the structures life cycle.

This paper presents an example of the use of two-dimensional, localized, high resolution hydrodynamic models to evaluate the flood risk of the Long Island Beach and upland, backwater areas. The flood risk is characterized for several different return periods (up to 1000-year). The coastal flood hazard was determined using the empirical simulation technique (EST) using observed gage data supplemented by simulation of synthetic tropical cyclones. The EST-calculated stage-frequency curve represents the combined coastal flood hazard due to both tropical and extratropical storms. Synthetic hydrographs were developed based on the combined coastal flood hazard and used as boundary conditions to a high resolution Riverflow2D model for Long Beach, which modeled the beaches, tidal inlets, rivers, marshes, and upland areas. The results of the model simulations were highly informative as to the cause and effect of both the beach and backwater, upland flooding and indicated where flood mitigation measures would be most effective. The results were used to establish the flood design basis for the design and construction of new critical infrastructure in the area, as well as design flood mitigation measures.

Here, we present two approaches for storm surge forecasting in coastal areas of Rhode Island: a regional ADCIRC model, and artificial intelligence (AI). Recent numerical modeling results published by north atlantic coast comprehensive study (NACSS) were employed as the basis. Using a downscaling approach, a high resolution ADCIRC hydrodynamic model was developed and interfaced with the NACCS model along the open boundaries. Although this model could effectively predict storm surges for the past historical/synthetic storms, it was numerically very expensive to provide boundary information for any storm surge forecasting scenario. To address this issue, an efficient AI data-based model was developed. The AI model predicts the storm surge using tropical storm parameters (i.e. central pressure, radius to maximum winds, forward velocity, and storm track). The AI model was validated using a set of randomly selected synthetic storms as well as real extreme storms in this region, and the performance was found satisfactory.

A frequent statistical problem in many coastal and off-shore engineering situations is to estimate the probability of structural failure expressed in terms of return period and design quantile. Usually, an univariate approach is carried out to quantify the risk of failure. However, coastal and off-shore structures typically fail because of the occurrence of a critical combination of the variables at play in a single sea storm: thus, it may be important to consider the joint occurrence of dangerous conditions. The present paper provides a sensible multivariate analysis of the available wave data at the Arabian Gulf, including a randomization procedure to cope with repeated observations. In addition, suitable strategies for performing multivariate design are presented and discussed.

Since Hurricane Katrina devastated New Orleans in 2005 and Hurricane Sandy ravaged New Jersey in 2012, it has been a common news story that U.S. East Coast storms are increasing. This study will show that, while the damage costs related to U.S. Atlantic Coast storms have increased in recent years, coastal flood events are not occurring more frequently or more severely. By negating the effects of global sea level rise, this study shows that the severity and frequency of extreme flood events has a similar trend over the past 100 years, which does not show a marked increase. NOAA monthly water level data for seven different locations on the East Coast of the United States was analyzed. The seven cities studied in this case study are places where Naval installations are located, as the authors are both Naval officers and are interested in the vulnerability of these federal assets.

The Gulf of Maine is frequently struck by Nor’easter storms during winter season. The strong wind produced by storm generates large waves and high surge, which may result in coastal inundation in low-lying areas along the coast when the storm peak coincides with high tide. In this paper, the state-of-the-art fully-coupled circulation and spectral wave model ADCIRC-UnSWAN was applied to investigate waves and circulation in the Gulf of Maine. The waves and surge level was well reproduced at wave buoy and tide gauge. While waves at offshore of Saco Bay reaches over 7.0 m at storm peak, it decreases rapidly when propagating into the bay, mainly caused by bottom friction and wave breaking. A clockwise circulation is identified at the offshore of Saco River. With the presence of waves, the clockwise circulation is greatly enhanced and moved further offshore. The surface elevation is also increased by 0.2m along the coast due to wave set-up.

Due to a variety of unique regulatory restrictions, designers of engineered solutions to coastal erosion in Massachusetts often are required to develop innovative projects that make the best use of limited resources. Three recent inlet management projects in southeastern Massachusetts provide useful examples of the competing interests that shape the engineering design process. The results of working together with the environmental regulatory community were efforts that led to balanced and unique solutions that enhanced barrier beach function as storm protection and habitat for the long-term. Because of endangered species habitat issues at all three locations, the effectiveness and sustainability of the enhancements needed to be unequivocally demonstrated to the permitting agencies.

The Social Vulnerability eXplorer (SV-X) system is being developed by the Army Corps of Engineers to aid understanding and communication of spatial distributions of vulnerable populations in hazard zones. SV-X’s interactive maps, tabular displays, and exportable datasets provide valuable insights into mitigations, preparedness, and response measures needed for areas of high social vulnerability to environmental hazard including floods, coastal storm surges, impacts, and erosion. This paper provides background on social vulnerability research supporting the development of the SV-X, and introduces the SV-X’s interactive web-based visualization and analysis tool for examining the social vulnerabilities of populations at risk from environmental hazard. The results are intended to help civil works project planners include social factors in their analysis of alternative risk reduction measures, and comparisons of “with-project” and “without-project” conditions. Disaster recovery planners may find utility in the SV-X’s ability to assess sizes and social vulnerability characteristics of populations in disaster impact zones.

Justification for evacuation and evacuation planning is sometimes questioned and there is a need develop approaches which justify the planning and associated expenditure. To this end, it was decided to carry out a pilot evaluation of the impact of a hurricane storm surge flooding on Brunswick, GA, using a dynamic agent based model that represents people's interactions with a flood and provides estimates of the number of people that are likely to be killed as a result of a flood event, as well as the time that is required for them to evacuate the area at risk. Climate change increase of 3ft in mean sea level would increase the population at risk in Brunswick by 20% for a category 4 hurricane. The modelling shows that for a category 4 hurricane managed evacuation can significantly reduce the number of fatalities.

Caltrans has been working on a fish passage/stream restoration project at the Solstice Creek Pacific Coast Highway (Highway) culvert in Malibu. They have been working with resource agencies and stakeholders to develop a sustainable solution to fish passage at the ocean outfall. The proposed design approach consists of removing the culvert invert, the concrete apron on the inlet side of the culvert, and the outlet apron on the beach to improve flow depths for fish migration. The new design will provide a more natural, stream-simulated condition through the existing culvert.

Superstorm Sandy destroyed the Rockaways Boardwalk on the Atlantic Coast of the Borough of Queens in New York City. The boardwalk was a 7.5 km long structure, with an average width of 9 m, running from Beach 20^th Street to Beach 126^th Street. The wooden boardwalk deck was lifted off of their concrete foundations, and some of the access stairways and ramps were washed away. All that remained in most locations was the boardwalk foundation; concrete piles and pile caps that had supported what the community had referred to as its “front street.”

This paper begins by exploring the current condition of Boston’s oldest waterfront infrastructure, namely, its granite blocks seawalls. The authors discuss the historic construction techniques and materials used to build the miles of granite block seawalls lining Boston Harbor. Having an understanding of the original construction, the authors use their experience with repairing and rehabilitating these seawalls by presenting various case studies and reports from past projects along the Boston waterfront. These examples illustrate the typical problems associated with these older seawalls. This paper also addresses the concerns associated with current localized coastal flooding along Boston’s waterfront, in addition to, potential problems arising from continued sea level rise and coastal inundation. Finally, this paper looks at examples of other coastal cities that have undergone extreme weather events and the studies and competitions that have been fueled by these events and what Boston might be able to learn from these disasters and solutions.

A plan to re-align the AMTRAK mainline in the Town of East Lyme, Connecticut, threatened to eliminate a public beach and provided an unworkable replacement to an existing elevated boardwalk. At the time, the Town was already engaged in the process of rehabilitating an adjacent 2,900-ft section of the “Niantic Bay Overlook” that directly connected to the elevated boardwalk that the AMTRAK project threatened. Through a cooperative engineering design process, the Town successfully worked with AMTRAK to create a workable solution that upgraded shore protection for the realigned AMTRAK corridor, re-created the public access along the beach, and enhanced existing beach resources. The entire project represents a design that is substantially more resilient to wave and flood damage, as beach width and overlook elevations were revised to reflect more stringent design protocols. The initial phase of the project consisted of AMTRAK’s realignment of the track system, requiring seaward encroachment of the railroad embankment onto the beach. The initial AMTRAK design replaced a wood pile walkway with a sheet pile seawall, armor stone revetment, and beach nourishment along the seaward edge of the railroad embankment. The final phase of the project is presently under construction and consists a 2,900-ft rehabilitation of a failed portion of the existing overlook that previously incorporated a relatively low-lying stone dust walkway fronted by a rip-rap revetment. Due to funding limitations, the revised design required use of as much of the existing overlook materials as practical. The final design consisted of raising the walkway approximately 3 feet by creating a steel sheet pile wall and utilizing the existing undersized rip-rap to stabilize the fronting beach. Where necessary, a full revetment cross-section fronting the sheet pile wall was designed, as well as repairs to the revetment slope between the existing railroad tracks and the reconstructed overlook pathway.

A lack of appropriate guidelines for the design and assessment hampers the development of multifunctional flood defenses like parking garages in quays and houses in dikes. The aim of the present paper, therefore, is to gain insight in the structural performance of multifunctional flood defenses and to provide a tool to evaluate design alternatives. For this purpose we have developed a generic method to determine the function of structural elements regarding flood protection. A study of diverse multifunctional flood defenses showed that the derived structural element types are indeed generic. We then applied the method to a real case, which showed that it factually provides more clarity and insight in the advantages and disadvantages of adding functions to flood defenses. This method will therefore advance the design and application of multifunctional flood defenses.

Coastal ecosystems provide multiple, valuable services including coastal protection but are globally threatened by human-induced and natural pressures. Traditionally, coastal protection has relied on hardening the shoreline using structures that are difficult to modify or remove once in place and, frequently have negative impacts on adjacent coastlines and coastal ecosystems. Consequently there is growing interest in the design and engineering of "nature-based solutions" (NBS) as elements of coastal protection that are flexible and sustainable and also help maintain or enhance ecosystem health. Despite the increasing interest and body of scientific research around NBS, there remains a gap with regard to guidance and understanding on how these solutions can be managed and integrated within traditional coastal engineering practice. This is partly due to the fact that NBS straddle two distinct disciplines–ecology and engineering. However, the coastal engineering profession has considerable expertise and experience with tools and approaches that can be applied to ecosystem based solutions. Likewise, the vast knowledge on the ecology of coastal ecosystems can help address many of the challenges raised by the consideration NBS for coastal protection. This work reviews the design approach and process within commonly used coastal engineering frameworks in the context of NBS, to find common grounds and overarching principles. Existing guidelines for traditional engineering structures are compared and contrasted with those for NBS to contextualize the position of NBS within engineering practice. A parallelism is thus drawn between NBS and traditional coastal engineering, acknowledging their differences, to provide insights on ways in which NBS can be integrated with standard coastal engineering practice, ultimately, to achieve the dual goals of coastal protection and habitat conservation.

This paper reports on a collaboration between Plymouth University and the General Lighthouse Authorities of the United Kingdom and Ireland, featuring the iconic Eddystone Lighthouse. A combined field observation and structural modelling pilot study was undertaken to shed light on how exposed rock lighthouses respond to wave impacts. Constraints to traditional monitoring methods are described and the solutions, along with some preliminary results from nearly 3000 measured events, are discussed. A finite element model of the Eddystone Lighthouse is briefly described and the modal frequencies are compared with the measured values from the field. These highlight a missing second modal response at 8 Hz which is the subject of on-going investigations.

Recently alternative shoreline stabilization approaches have become increasingly common in the urban northeastern United States. The occurrence of Superstorm Sandy just several months after the completion of two neighboring projects in the Bronx, NY, presented a unique opportunity to examine the performance of non-traditional shoreline projects under extreme conditions. The assessment of the two projects along the East River was part of a larger forensic analysis in which the performance of a total of six traditional and non-traditional shoreline projects was undertaken. Of the two Bronx, NY, sites, Hunts Point received significantly less damage due to its more robust design and more natural gentle slope. At Oak Point, debris impact and scour impacting an oversteep slope were found to be the primary damage mechanisms.

As part of The Hudson River Sustainable Shorelines Project, a multi-year effort lead by the New York State Department of Environmental Conservation Hudson River National Estuarine Research Reserve (), a forensic analysis was performed to investigate the site conditions of six alternative shoreline stabilization treatments, that were impacted by Tropical Storms Irene and Lee in 2011 and Post-Tropical Storm Sandy in 2012. Project objectives included: determining patterns among those structures that survived and those that did not; determining which aspects of structural maintenance lead to the failure/survival; determining the potential impacts from extreme waves, water levels, and increased currents; and determining the impact of vegetation on structure failure/survival. The following tasks were completed as part of the forensic analysis: a review of previous shoreline stabilization attempts, a characterization of the conditions at each site, the collection of all available engineering/design data, post-storm field data collection, and hind-casting of the storm conditions. Factors that were found to lead to the failure of structures included the use of undersized or improperly graded stone, the implementation of inappropriate slopes, and immature vegetation. Severe erosion and scour were caused by large floating debris and were determined to be the primary cause of damage at several of the sites. Impacts were more severe along shorelines with steep slopes, with large waves and heavy debris scouring away soil and vegetation. Common factors amongst those structures that survived the storms with minimal damage included sloping terraces and adequately sized stones, as well as the presence of engineered structural elements for armoring. Mature vegetation with established root systems was determined to be a critical factor for the survival of the plantings. In addition, project maintenance and where necessary, adaptive management was also identified as a key factor in determining performance.

The push for creating environmentally more compatible shore and harbor protection often puts the reality of the needs for resilience and strength at odds with the needs of nature. Softer protection schemes such as floating wave attenuators and non-bottom founded protection methods are typically inadequate to resist the ravages of the storm, while the construction of solid ring breakwaters change the texture of the shoreline and affect the biota. Out-of-the-box thinking was required to find an approach that could both emulate the natural environment and yet still be resilient enough to protect against hurricane events, promote ecology, and offer safe and manageable navigation. The solution was found in building a protection system of artificial islands configured to create wave sheltering, oriented to reduce long term sedimentation effects by controlling tidal flow patterns, and executed to be a living island archipelago with both benthic and terrestrial habitat.

This study presents a field investigation to qualitatively examine wave setup induced water ponding/piling-up behind a low-crested engineered oyster reef breakwater structure. Field monitoring of a prototype breakwater segment located near Alabama Port, Alabama, in May 2015 did not reveal significant changes in the mean water levels near the breakwater prototype location. The typical wave climate observed during the monitoring period consisted of short-crested wave heights of less than 0.1 m with wave transmission as high as 78% of the incident wave height. Collectively, the mild wave climate and the poor wave attenuation capabilities of the low-crested breakwater structure likely prevented the development of wave setup during the monitoring period. It is recommended that further studies continue to investigate hydrodynamic interactions related to low-crested oyster reef breakwater structures used in living shoreline stabilization projects, particularly during storm events or more energetic conditions.

The use of artificial reefs as wave attenuating structures is becoming more common in the design of living shoreline projects. Unfortunately, their behavior and performance are not widely known. A series of geometrically scaled laboratory experiments were conducted to measure wave transmission behind bagged oyster shell breakwaters, concrete wave transmission frustums, and triangular oyster shell cages. The experiments covered a range of water depths and wave characteristics representative of conditions commonly encountered at project sites throughout the Gulf Coast. The wave attenuating capabilities of the various structures are described in terms of hydrodynamic parameters and structure geometries. Experimental results reveal strong correlations between wave transmission and simple, dimensionless parameters. However, existing methods for estimating wave transmission through rubble mound structures do not provide accurate estimates for these structures. This work will lead to the development of simple predictive equations for estimating wave transmission coefficients, within an appropriate range of uncertainty, for these complex and unique non-rock alternatives.

A set of 9 artificial oyster reef products were proposed for use in an erosion control project in coastal Louisiana with the goal of reducing shoreline retreat and providing ecosystem benefits through creation of a platform for oyster growth, thus creating a living shoreline. Performance characteristics of available artificial oyster reef products are limited due to the experimental nature of the products. Their performance in terms of wave energy reduction and unit stability are generally poorly understood with available data. Due to the large number of different units, potential variability in unit geometry, and high costs for physical modeling, the artificial oyster reef structures were analyzed using the 3-D volume of fluids CFD model FLOW3D, with 3D structure models integrated into the model. The structures tested included a typical low-crested rock breakwater for the purpose of model wave transmission validation, as well as fixed and floating concrete precast units. A range of wave conditions were tested and the results of interest included wave transmission over/through the structures, as well as hydrodynamic loads on the structures for use in design. The CFD modeling was performed in a manner analogous to a full scale laboratory experiment with sufficient units included to capture variability in wave transmission along the length of the structure. Modeling results were used to evaluate wave energy reduction performance, hydrodynamic stability, and as part of an evaluation of artificial oyster reef overall cost-effectiveness.

This study assesses the effectiveness of linear berms versus circular mounds to reduce wave height for wetland restoration. The Hamilton Wetlands are modeled using the phase-average spectral wave model STWAVE. The model is first validated with field data. The model results show that the berms are approximately twice as effective in attenuating the wave height as circular mounds of approximately the same volume. The presence of vegetation on the berms and mounds increases wave attenuation as long as the water depth is sufficient to submerge the vegetation. Because the circular mounds have more vegetated area, the vegetation induces greater additional attenuation for the mounds than the berms. Berms provide a longer extent of high crest elevations for the same volume of sediment compared to mounds, so are in general more effective in attenuating waves.

A series of experiments investigating the dissipation of wave energy by artificial Spartina alterniflora were completed using a large-scale flume at the U.S. Army Engineer Research and Development Center. A previous experiment identified trends in wave attenuation with respect to hydrodynamic and plant parameters, changes in spectral shape, and parameterized the bulk drag coefficient. However, the trends with respect to wave height and peak period were indefinite and unexplained behavior of the bulk drag coefficient between submerged and emergent conditions led to a subsequent experiment that spanned a wider range of Reynolds numbers and degrees of plant submergence. Plant submergence is again shown to be a crucial variable affecting the degree of wave attenuation. Wave attenuation slightly increased with wave height at all modeled water depths whereas wave attenuation with respect to peak wave period depended on plant submergence. Accounting for bottom friction in the Mendez and Losada (2004) approach better collapsed the bulk drag coefficient across water levels, although two different curves, one for emergent and one for submerged conditions, were evident.

Quantifying the penetration depth of a dragging anchor on a horizontal layer of rockfill provides the possibility to optimize the layer thickness of rockfill layers with a protective function. Current research on this subject is limited and is often aimed at anchor capacities in sand and clay. Penetration behaviour in rockfill is mainly investigated for protections with a limited width. Anchor dragging tests carried out for a canal expansion project show that as the rock size increases, the penetration depth and the holding capacity of the anchor decrease. A semi-empirical prediction formula is derived. An additional series of scaled down tests shows that the process of anchor drag in rockfill is scalable, as long as all aspects of the trial design are taken into account. This provides possibilities for accessible further research, expanding on the prediction of penetration depth and further anchor behaviour in different types of rockfill.

During the last two decades, the Port Authority has developed an enormous work of design and construction to expand its facilities and develop a new basin in Punta Langosteira. In 2011, it was completed the construction of the main breakwater, 3.35 km long, exposed to the harshest design conditions, Hs[m]=15.1 and Tp[yr]=140. The Port sheltering was completed during the years 2013 and 2014 by the Port Authority of A Coruña with the collaboration of GEAMA group from the University of A Coruña, developing the design of the secondary breakwater of the port. The works are under construction, with the completion planned in 2016.The aim of the paper is to present the design procedure to analyze and reflect on critical issues, in addition, present the potentialities of probabilistic methods applied to rubble-mound breakwater design.

Currently, there are many available formulae to calculate the required rock size in the toe berm of the structure. The stability number, N_s, is assumed to be linearly proportional to the incident wave height. However, the incident wave characteristics are transformed by the presence of the breakwater and the oscillation patterns in front of the structure is the sum of the incident and reflected waves. The objective of this work was to analyze the toe berm stability as a function of the total wave height in front of the breakwater (H_f). The study was done applying the hydraulic performance curves proposed by Vílchez et al. (2016) to data from van Gent and van der Werf (2014) in order to evaluate the complex reflection coefficient (modulus and phase). It is shown here that the influence of the wave steepness disappears if the total wave height in front of the breakwater is used instead of the incident wave height. The reason is that the influence of this variable is already included in the value of H_f.

The mechanical and hydrodynamic efficiency of a new wave energy converter device, called MICO, is presented in this paper. MICO is a point absorber WEC, consisting of a floating buoy attached to a long lever that conveys the mechanical energy to the generator. The device was tested in a wave flume at the National University of Mexico, using a small-scale model. The experimental work focused on improving the design of the WEC and obtaining empirical relations to determine its optimal geometry as a function of wave conditions. Results from these tests gave the optimum dimensions for the diameter of the buoy and the length of the lever, as well as information on the sea states for which the device would have best responses. The experimental results showed that MICO is more efficient in sea climates with steep waves, i.e. short periods associated with large wave heights. The main advantages of MICO are its low maintenance costs and its environmentally friendly operation.

The following paper presents a case study of the Village of Surfside, Texas, where various coastal structures have been analyzed, designed, constructed, and monitored. The lessons learned from the performance of a revetment during Hurricane Ike is presented, which was assessed after the storm and modifications were implemented at various stages to ensure its future performance. The various structural and non-structural solutions that were proposed aim to increase the resiliency of the Village of Surfside’s coastal community. This paper also discusses the unique hydrodynamic and morphodynamic conditions at this site due to the receding delta, navigation channel, and jetties, the solutions that have been proposed and the priority of implementation based on funding constraints. The features that have been constructed have been tested during extreme events and were monitored to determine their performance. The revetment structure has been enhanced two times since its original construction to adapt to the damage experienced during Hurricane Ike and increased ongoing erosion due to a hot spot near its terminus. Future erosion response project construction work in the area will likely consist of groins, which would be implemented as part of the overall resiliency plan for the community.

Information regarding the likelihood of structural failure of flood defences forms an essential part of any flood risk analysis (FRA). At present, when conducting FRA the probability of a defence failing is expressed conditionally upon a single variable either a hydraulic loading or a composite variable—a function of several hydraulic loading variables. A methodology has recently been proposed for simulating realistic sets of extreme nearshore sea conditions that comprises all of the hydraulic loading variables that can combine to produce an extreme sea state. By acting as the boundary conditions for a coastal FRA, the methodology has opened up the possibility of incorporating more detailed representations of the susceptibility of a coastal defence structure to failure into such analyses. It is anticipated that this more accurate description of a structure’s likelihood of failure will ultimately lead to more accurate flood risk estimates. In this paper, the newly derived fragility representations are introduced before the difference/improvement in their description of a defence’s susceptibility to failure is assessed by comparing the annual failure probabilities given by the new and existing representations.

Coastal communities in low-income countries are often very vulnerable to storm surges. Many low-income countries have achieved considerable success in increasing the resilience of their populations to coastal flooding and tropical cyclones. For example, the Bangladesh Cyclone Preparedness Programme has successfully warned, evacuated and sheltered millions of people from cyclones since its inception in the early 1970s, reducing loss of life from extreme cyclonic events by several orders of magnitude. Cuba is affected by hurricanes that often hit the U.S.A. However, when normalized the number of deaths caused by recent hurricanes is 20 times lower in Cuba than it is in the U.S.A. This paper briefly examines how Bangladesh and Cuba, have increased their social resilience to coastal flooding and whether the lessons learnt are transferable to disadvantaged coastal communities in the U.S.A. in order to assist them in improving their own resilience to hurricanes and coastal flooding.

Flooding has been regarded as one of the main natural hazards threatening central Europe and the United States of America (U.S.); its destructive impacts on life, economy, and environment could spread from areas regularly exposed to water to those that are some distance from watercourses and lakes. Estimating regional flood risk is a crucial part of the decision making process undertaken by government mitigating agencies, catastrophe risk managers, and insurance companies to optimally allocate resources and develop sound business strategies. Furthermore, flood losses must be kept as small as possible by the use of flood mitigating measures. However, data about the effects of these measures are rare and consequently the decrease of losses by reducing vulnerability is unclear. To address the above two challenges, a comprehensive loss estimation model was developed, for central Europe and U.S. separately, to estimate inland flood risk and quantify the effects of mitigation measures. The model framework incorporates the event-based fully-probabilistic meteorological hazard model and vulnerability model. The vulnerability model used incorporates a component based approach to capture losses from inland flood events utilizing important structural and regional features such as construction, occupancy types, and building height.

The objective of this study was to create a generalized risk assessment tool for assessing the vulnerability of Rhode Island marinas to storm surge and sea level rise. A vulnerability assessment tool was developed to evaluate the infrastructure and environmental conditions at a marina in the form of a detailed questionnaire to be completed by marina operators. Supporting environmental information was provided online for the entire Rhode Island coastline. The assessment was applied to two marinas: Brewer Greenwich Bay Marina in Warwick, RI, and Brewer Cove Haven Marina in Barrington, RI. Flood maps including wave effects were generated for 25, 50, and 100-year return period events with 0.30, 0.91, and 1.52 meters (1, 3, and 5 feet) of sea level rise for both marinas. Based on the assessment, Brewer Greenwich Bay Marina was given a high risk designation based on environmental conditions, and a moderate risk designation based on its infrastructure. Due to its moderate infrastructure risk designation, the breakwater, piles, and wave fence at this location were evaluated and redesigned to prevent failure. Brewer Cove Haven Marina received a moderate risk designation in both assessment sections and no mitigation measures were recommended. This assessment tool is now available for use throughout Rhode Island as a planning tool to help marina operators identify areas of weakness and prepare for the effects of storm surge and sea level rise on their facilities.

The ten Northfrisian Halligen are small undiked marsh islands. They are located in the German part of the UNESCO World Natural Heritage Wadden Sea. The houses of the inhabitants are built on artificial dwelling mounds and during storm events these mounds are the only places which are not completely inundated on the islands. The design of these artificial dwelling mounds is mainly based on tradition and no scientific design approach exists. In order to prioritize protection measures for the different dwelling mounds, a safety standard has to be defined. The most important criterion for safety during storm surges is the water depth due to wave overtopping on the dwelling mound. For this reason, maximum allowed water depths on the dwelling mounds are defined. Numerical simulations are performed to simulate the water depths due to wave overtopping on the dwelling mounds and to test the compliance of safety standards.

Shoreline protection is an important but confusing and costly endeavor for small municipalities. Which material should be used? What are the financial costs related to the project? What are the environmental impacts of the project? Can the project be permitted by the federal government and state government? These are some of the questions that every shoreline protection project must tackle. This paper details the process that Ocean City, New Jersey, went through to select a shoreline protection project for a vulnerable stretch of beaches on the north end of the island. The shore protection project was completed in the spring of 2011 almost 18 months prior to Hurricane Sandy. Ocean City is located south of Atlantic City and is 11 miles south of the landfall of the eye of Sandy. The paper will detail the impacts of Hurricane Sandy on the shoreline protection project.

The coastlines of the Caribbean are unique in many ways. Their warm waters and sandy beaches attract millions of visitors to their shores and these attributes provide an essential economic opportunity. Coastal hazards affecting the region include hurricanes, tsunami, and coastal erosion. For islands with mountainous interiors, development is often concentrated along the coastlines. This paper draws on more than 20 years of experience designing and evaluating coastal protection schemes in the region, and the related issues, constraints and opportunities are discussed. Projects in the Bahamas, St. Vincent, Guyana, Jamaica, and Barbados are cited and the reasons for their appropriateness to the region and specific locations are highlighted. The paper highlights the importance of multi-criteria analyses for coastal project selection and the need for funding agencies to insist on a thorough evaluation of options at the design stage. The unique nature of both the local and regional issues must be recognized and, as such, the design parameters used must have a Caribbean focus. Stakeholder consultation is an essential component of the design process and projects should be treated as an opportunity for socio-economic enhancement as much as possible. Eco-system based approaches should also be given due consideration. Experience has shown that the regulations and codes that govern coastal development need to be updated in most cases. Further, proper enforcement of these regulations will be key if Caribbean coastlines are to survive the next century of anticipated sea level rise.

Resilience is a ubiquitous term in the aftermath of hurricanes Isabel, Katrina, and Sandy. Nevertheless, there have been few attempts to quantify resilience in coastal engineering practice. This paper addresses this gap and presents a method to quantify resilience. The basic concept is to integrate: (1) Structure/Beach damage during a storm and (2) Time needed to recover from storm damage. Both items need to be summed over a range of storm return periods. The above integration provides a single numerical score that can be used to rank alternative coastal structure and beach nourishment plans. The methodology is based on the work of Chang and Shinozuka (2004) in the context of earthquake engineering and has been recently advanced by Schultz and Smith in preparation (2015).

In a bold experiment, the Basque Government constructed an innovative oscillating water column (OWC) power station breakwater outside the small fishing port of Mutriku during 2007-2008. While the main structure was a rubble mound, the OWC section of the breakwater consisted of 16 chambered vertical wall units formed by stacked concrete layers. Before the power station could be completed however, storms hit the breakwater in December 2007 and March 2008). A further storm in January 2009 result in severe structural damage to a number of the OWC cells. Previous papers have explained some of the contributions to damage, but have not described detailed flows, loads, and consequent responses. In order to understand the causes of the damage, this paper will describe recent numerical model (CFD) experiments to calculate flows, pressures, and resulting loads at critical positions within the OWC cells, both for the intended operational condition (H_s=8m, T_P=12.8s), and January 2009 storm wave conditions (H_s=13.7m, T_P=14.5s). OpenFOAM CFD modelling tools have been used, supported in part by contemporaneous large scale physical model tests in the GWK in Hannover. The CFD modelling has examined key flow processes and dynamic pressures to explore whether these may explain the onset of damage to the OWC cells. Modelling so far suggests that impulsive pressures were developed within OWC chambers where the air turbine or control valves had not been fitted. Around critical corners of the front face and OWC chamber, flows, and pressures following impulsive processes may have seen the onset of cavitation, potentially leading to localised failures, particularly at joints between the stacked cell units.

This paper presents results of the physical experiments that were performed to investigate horizontal wave loading acting on the perforated caisson breakwater having two wave chambers. The main focus of this research was placed on evaluation of the maximum horizontal force on the porous middle wall between the two wave chambers, which was found to be on average less than half of the estimate by Goda's formula for the solid wall. This implies that the peak wave loading on the middle wall is comparatively smaller than those on the front or rear walls of the double-chamber perforated caisson.

Coastal design guidance is available to estimate structural forces caused by waves breaking against vertical surfaces. Studies have been made to evaluate forces created by these significant hydrodynamic transient forces. Studies on both rigid wall and scale-model wood structures from wave impacts have shown that there is a time delay between the initial wave contact and the peak deflection recorded. This delay is generally consistent for individual systems and structures, regardless of wave size or orientation. The purpose of this study is to review existing literature and to evaluate possible explanations for this phenomenon observed in wave tank studies at OSU (Oregon State University). It is proposed that structural response to wave impact loads is analogous to that created by seismic events. Following theories are proposed based on literature review and analyses. These are required to be confirmed through additional research. 1. Structures respond to coastal wave impacts similar to forces created by seismic events. Buildings or walls respond to wave forces based on natural or fundamental frequencies of structural systems impacted. 2. Building uplift forces and horizontal deflection vary based on wave characteristics, but the time to the peak response does not. Waves generate negative acceleration upon initial impact. The presence of water around the structure after impact appears to dampen the deceleration phase. 3. Normalized equations are developed that predict deflections and time to peak. The fundamental deflection equation appears to be primarily a function of a peak k_g value, gravity coefficient, and time. The harmonic portion of the equation is a cubic parabola function of the natural frequency of the impacted structural system. 4. A peak k_g function determines magnitude of deflection and appears to be predominantly a sigmoidal curve distribution function of the structures inertia and wave heights. Oscillation frequencies create minor transients as structures and waves interact. These findings if expanded and validated by further research can simplify wave force analysis for onshore coastal structures. It can also potentially reduce damages to structures and resulting financial losses due to storm surge.

An investigation of the lateral restraining stiffness effect on the bridge deck-wave interaction under hurricane waves is conducted numerically using a dynamic mesh updating technique. At first, a mass-spring-damper system is implemented in a commercial CFD program in order to realize that the bridge superstructure can vibrate laterally under the wave actions. Then, a wave model based on the Stokes 2^nd order wave theory is developed and verified with analytical solutions. The shear stress transport (SST) k-ω model is used as the turbulence closure for the RANS equations. This developed methodology is further verified with experimental measurements in the literature which assures its valid applications in the following parametric study. Finally, general characteristics of the structural vibration and the wave forces are observed and discussed through a parametric study. The obtained results show that increasing the structural flexibilities in the lateral/transverse direction does not necessarily benefit the bridge structure with an obvious force reduction for both the horizontal and vertical forces on the bridge superstructure.

In the design of breakwaters, the wave pressures out of the surf zone are estimated by the maximum wave height which corresponds to the 1.8 times of significant wave height according to Rayleigh theory. On the other hand, the nonlinear four-wave interactions can lead to a significant enhancement of occurrence frequency of extreme waves whose height can exceed above maximum wave height. It is necessary to appropriately evaluate the effects of the deviation from Rayleigh theory on the wave pressures acting on breakwaters under extreme wave conditions. In this study, the analyses of data obtained from the physical experiments in a wave tank were conducted through the comparison with the numerical simulations based on the Boussinesq equations. As a result, it is possible to evaluate the uncertainty of the wave pressures including the deviation from the Rayleigh theory by using the occurrence frequency of the maximum wave height depending on the kurtosis changing.

Extreme storm events and a potential sea level rise are great threats for low lying areas, e.g. in Belgium. Both the wave-induced loading and wave overtopping of vertical coastal structures are identified as the main challenges with respect to coasts in low-lying countries. Therefore, the overall objectives of this study are to understand and measure wave-induced loads on vertical storm walls caused by overtopping waves and shallow foreshores. Hydraulic model tests were performed (scale 1:25) in the wave flume of the Department of Civil Engineering at Ghent University. The foreshore (1:35) and the dike (1:2) were built with two different dike crest levels (+9 mTAW and +10 mTAW) and two promenade widths (10 m and 30 m). The analysis of the tests showed that the interaction between overtopping rate, freeboard, wave conditions and water level influences the wave-induced loads significantly. Empirical relationships were developed for the present setup combining the dimensionless force with the dimensionless overtopping.

The so-called post-overtopping processes are of wide interest for coastal engineers. Dedicated middle-scale tests have been carried out to measure impacts of an overtopped wave on a storm wall at low freeboard coastal structures. A smooth dike slope and a vertical wall, both with a promenade at crest level and a storm wall at the end of it, have been tested in a scale of 1/6. Impacts have been measured both with pressure and force transducers; the two systems provided similar results. A correlation between the hydraulic conditions and the wave impacts on the storm wall is proposed. Further analysis is ongoing to also include the post-overtopping characteristics to increase insight on the acting parameters in this process.

In recent years, the required performance of breakwaters against tsunamis or high waves is increased. In Japan, the design concept of breakwater has been changed after the 2011 off the Pacific Coast of Tohoku earthquake with subsequent huge tsunami. However, the details of property of such huge waves are not studied sufficiently due to difficulty in measuring them, and thus, numerical approach is increasingly expected as the alternative. This paper presents numerical simulations targeting composite phenomenon with overflows and overtopping waves acting on breakwaters by using the recently developed accurate particle methods with a porous model for reproduction of permeability of caisson mounds. From the results of the numerical simulations, the structural effectiveness of the breakwaters with a parapet is discussed from the viewpoint of the wave pressure and velocity fields of overflows.

Experiments were conducted to analyze the commonly accepted assumptions of the linearity of the uplift pressure on crown walls and the simultaneity of the occurrence of their maximum values with those of the horizontal pressures. A small-scale model of a rubble mound breakwater with an “L” shaped concrete crown wall was tested in a wave flume. Regarding the vertical pressure distribution, its non-linearity was evidenced and it was found that its dynamics and unpredictability increase as the vertical position of the crown wall is close to, or lower than, the still water level. A simple model for estimating the uplift pressure is presented and a 3D numerical model, Flow 3D, was calibrated and tuned to serve as a tool for further tests.

Impulsive pressure acting on an upright wall is usually generated when the mound is relatively high, the berm width is suitably wide or the slope gradient is gentle. However, it is also liable to be generated when the bottom slope is steeper than about 1/30, and the Goda formula is not applicable to such cases. In the present study, several application methods for extended Goda formula, as well as the numerical simulation (CADMAS-SURF) were investigated to compare the experimental results of impulsive pressure generated on a steeply sloping sea bottom. The impulsive pressure on the steeply sloping sea bottom can be estimated extended Goda pressure formula regarding the slope in front of the wall as a foundation mound and using the breaking wave height. The impulsive pressure on the steeply sloping sea bottom also can be reproduced by the numerical simulation (CADMAS-SURF).

Rubble-mound breakwaters using granular cover layers of rock or concrete units are mainly designed using empirical equations, scaled hydraulics laboratory test models and precedent practice. Multi-body solids numerical models can now represent the geometry and contact forces in such armour systems, when at rest or in a dynamic state of motion. The challenge tackled in this paper is to introduce oscillatory wave disturbance forces to such solids models with sufficient realism so that useful new numerical model information on armour stability can be used by designers. This is achieved using advanced 3D numerical wave tank simulations of wave-induced fluid flows inside the armour and under layers. Pressure-time histories of 2D sea states are also modelled enabling longer runs and entire storm sea states to be investigated for the equivalent rubble-mound structure. The correctly calibrated pressure-time storm history for the entire 3D domain heralds the introduction of a new ‘wave proxy’ method, based on the multi-body solids FEMDEM solver, Solidity. The integrated surface pressures acting on units yield the required oscillatory hydraulic and buoyancy forces. These drive the potential instability and movements and are superimposed on each unit in combination with the constantly updated contact, inertia and body forces. Results of this ‘one-way’ coupling method are briefly illustrated. We compare the effect of two different extreme storm conditions on the stability of a Core-Loc structure.

A good understanding of the overtopping performance of a structure involves not only the determination of the average overtopping rates but also of the individual overtopping volumes. However the knowledge on individual overtopping volumes in literature is still limited for specific conditions. To improve the understanding of individual overtopping volumes on steep low-crested structures in deep water, we performed 2D physical model tests for these conditions, with additional wave-per-wave overtopping volume measurements. This paper summarizes the knowledge on individual overtopping volumes, describes the physical model tests, and analyses the individual overtopping distribution and probability of overtopping of the dataset. The shape factor b of the Weibull distribution of individual overtopping volumes increased for increasing relative crest freeboards and for milder slopes; while the probability of overtopping decreased for increasing relative crest freeboards. The existing prediction formulae for b values performed well although slightly overpredicting the results. The probability of overtopping is consistently overpredicted by all the formulae.

Wave overtopping measurements acquired during the FlowDike small-scale physical model tests were analyzed to extract information related to individual overtopping waves. Individual overtopping wave volumes and associated hydraulic parameters were determined at the seaward edge of the model dike crest for normally-incident wave conditions impinging on either a 1V:3H or 1V:6H planar seaward-side dike slope. A two-step “supervised” procedure was used that combined the best features of automated wave volume determination along with manual error correction. This resulted in a well-vetted data set consisting of 5,799 individual overtopping wave volumes. New empirical relationships are presented for the maximum velocity, maximum flow thickness, maximum instantaneous discharge per unit crest length, and overtopping duration as functions of individual wave volume, and in some cases, mean spectral wave period.

This paper focuses on new methods that have been implemented and tested in the artificial neural network (ANN) recently developed by the authors to predict the wave overtopping discharge. An improved representation of the non-significant wave overtopping conditions can be obtained by extending the training database of the existing ANN to include all the non-zero values. The modification of the ANN architecture by the set-up of a classifier-quantifier scheme to improve the prediction of both low and high values of the overtopping is also investigated and discussed. The accuracy of the improved ANN is finally verified through the prediction of new datasets.

A new wave run-up simulator has been designed, constructed, calibrated and used for testing of the seaward face of dikes. The upper part of dikes or levees often have a clay layer with a grass cover. The new device is able to test the strength of the grass cover under simulation of up-rushing waves for pre-defined storm conditions. The cumulative overload method has been developed to describe the strength of grass covers on the crest and landward side of dikes, for overtopping wave volumes. In essence there is not a lot of difference between the hydraulic load from an overtopping wave volume or from an up-rushing wave. Therefore the hypothesis has been evaluated that the cumulative overload method should also be applicable for up-rushing waves. Tests on a real dike have been used to validate this hypothesis. The main conclusions are that the new wave overtopping simulator works really well, but that the results on testing till so far has not yet been sufficient for a full validation of the method. More research is required.

This paper describes a review and analysis of available hydraulic model tests on overspill basins at the crest of sloping structures. Based on an analysis of these tests, further model tests were performed in the wave flume of Ghent University (Belgium) to determine the wave overtopping rate for smooth impermeable sloping structures with various sized overspill basins at the crest. The different test set-ups and test parameters are presented in this paper. Results of the wave overtopping rates are then discussed and extensions to the existing overtopping prediction formulae are proposed. The fitting of the new formula to the different data sets is discussed and the influence of various key geometric parameters is analyzed in detail.

We present a series of complementary physical experiments and numerical model simulations based on a coupled Boussinesq-nonlinear shallow water equation scheme to investigate extreme wave runup on a plane beach. Extreme incident waves are modelled as focused wave groups using the NewWave design wave, and the maximum runup elevations generated by these focused waves are compared to the extreme runup elevations recorded during related irregular wave runup simulations. The maximum runup of a focused wave group exhibits strong dependence on the linear amplitude, focus location and phase at focus of the focused wave group. The extreme values of irregular wave runup in a random sea compare well to the runup values from equivalent incident focused wave groups with amplitudes set with Rayleigh statistics and optimised focus position and phase.

This paper will explore the process of ‘suffusion’–the movement of fine material through the voids of a granular matrix with particular reference to the retention of sand-fill by a rubble bund. Guidance on suffusion has hitherto been derived for rock-fill dams, where hydraulic gradients are steep, and persist for the life of the dam. In contrast, sand protected by rubble mound bunds will experience hydraulic gradients that are much smaller, and intermittent. The paper presents a series of empirical analyses and physical model tests for an idealised defence in which detailed pressure measurements within the rubble bund were used to define representative hydraulic gradients. Test data from studies on onset of movement of fine materials reported in 1991 were then used to identify where hydraulic gradients were sufficiently reduced to avoid significant loss of sand-fill.

Eight tests in a wave flume with a sand beach were performed in order to examine the reaction of ten wooden blocks (idealized houses) on the foreshore and berm as well as on short and long pilings. The still water level was varied to create accretional and erosional profile changes on the foreshore and berm. The cross-shore wave transformation on the beach and the wave overtopping and overwash of the berm were measured in 71 runs of irregular waves where each run lasted 400 s. The initial block elevation above the sand surface is shown to have little effect on the hydrodynamics, sediment transport, and profile evolution in this experiment with widely-spaced blocks. The block floating and sliding on the sand surface and the block falling from the pilings depended partly on the block elevation above the still water level but on the swash hydrodynamics and block clearance above the foreshore and berm whose profile varied during each test.

This paper presents the development of an innovative design to adopt geotextile tubes as core in a concrete Core-Loc breakwater. The concept was considered as both a valuable engineering exercise (cost and time saving) to take advantage of abundance of both dredged material and volcanic sand at the remote project site. The paper details the number of design challenges that were considered through the breakwater’s design development and 2D physical modelling study. A comparison is then presented between the geotextile tube breakwater and a traditional breakwater of rock core, with resulting conclusions and recommendations.

In this paper, an integrated model is proposed to investigate the wave-induced seabed stability around a breakwater on a sloping seabed. In the present model, the Volume-Average/Reynolds Averaged Navier-Stokes (VARANS) equations are used for wave simulation, while the Biot’s poro-elastic equation is used to govern the soil model. Unlike previous studies, pre-consolidation due to hydrostatic and the structure are considered in this model. Based on the proposed model, the effects of wave characteristics and seabed slopes on the wave-induced seabed instability (including liquefaction and shear failure) in the vicinity of a breakwater are investigated. Numerical results indicate that the wave-induced seabed instability is more likely to occur in a steep slope and under large wave loading.

This paper presents the results of an experimental investigation performed to understand the occurrence of scour in front of a vertical seawall. A single wave steepened by an artificial slope that breaks on the seawall or as close as possible to it was generated. For this purpose, a physical model was constructed and placed in a 2D wave flume where a focused wave group was generated at the toe of the fore slope. Three distinctive sediment types for the slope were tested (sand and two gravel sizes) and the experimental program included tests with different slope angles, relative submergence, still water depths and energy spectra (Jonswap and Top-Hat). Empirical models for the prediction of scour as a function of the maximum wave height at toe of the slope were obtained for the sand and smallest gravel slopes.

Permeable coastal structures typically contain granular filters in one or more layers. These filters are normally geometrically tight to prevent material washout. A cheaper alternative is a geometrically open filter where only minimal base material loss or settlement occurs. In Van Gent and Wolters (2015) physical model tests were performed to estimate the amount of erosion and accretion of sand underneath one or two layers of rock. Here, a numerical model has been applied to compute hydraulic gradients at the internal sand-rock interface for conditions in which the structure is exposed to wave action. The results show that the model can accurately compute hydraulic gradients at the internal rock-sand interface and that the position of erosion and accretion of sand can be predicted. The performed parameter analysis shows which parameters affect the hydraulic gradients and which parameters do not. Moreover, processes that contribute to erosion and accretion have been analysed.

This paper describes the design process and hydraulic stability tests corresponding to the western breakwater in the outer port at Punta Langosteira (A Coruña, Spain). This breakwater is the second phase of the 1.35 km-long secondary breakwater; the first phase was the single-layer Cubipod armored southern breakwater. The western breakwater is protected with a single-layer 25- and 30-tonne Cubipod armor in the trunk and a double-layer 45-tonne Cubipod armor in roundhead. The design was validated with small-scale 3D tests of the two alignments of trunk and the roundhead. 1,360 15- and 25-tonne Cubipod units are being re-used from the Southern and Northern breakwaters, completed in 2012 and 2013, respectively. 6,670 new 25-, 30-and 45-tonne Cubipods were manufactured using 25 vertical formworks and 87 bases, in a 24 hour/day work cycle and 3.5 units/day/formwork with a 6-hour demolding time; 1,100 m³/day of concrete was consumed and Cubipods were piled up to five levels. The construction of the western breakwater started in April 2015; armor is being completed before the winter season and a crown-wall is planned to be built during the summer of 2016.

The role of physical modelling in advancing port design is demonstrated by means of a case study in which three-dimensional physical modeling is used to guide the design of an offshore logistics support base being developed at an unprotected site on the coast of Brazil. The project was driven by the need for a safe harbour for offshore supply vessels, to prevent vessel damage and damage to the dock and berth during normal operations, as well as during extreme storm events. A 1:70 scale model of the proposed supply port and a portion of the surrounding bathymetry was designed, constructed, operated, and then modified to simulate several alternative layouts and design concepts. Froude scaling laws were applied to estimate prototype behaviour from observations and measurements in the model. The physical model proved to be an effective method for assessing the operability of the new port in various metocean conditions and for optimizing its design. It allowed the design team to investigate and assess the impact of many factors influencing wave conditions and the corresponding behaviour of a moored drill supply ship in an efficient and cost-effective manner. The important influences of wave direction, wave height, wave period, and water level were investigated, as were the sensitivities to ship location, loading condition, mooring configuration, mooring line pretension, and mooring line stiffness. Numerous modifications to the port layout were also investigated, which included lengthening the main breakwater, altering the entrance geometry, constructing a new offshore breakwater (of several different lengths), and widening the navigation channel. The outputs from the physical model study have been used in combination with information on the local wave climate at the site to assess operability and estimate downtime due to adverse weather for different port layout and breakwater configurations.

In 2012 Amtrak replaced a 1907-era bascule bridge over the Niantic River at East Lyme and Waterford, Connecticut. The new bridge was parallel with and 58 feet south of the bridge it replaced. Its construction closer to Niantic Bay, an arm of Long Island Sound, displaced an existing recreational beach and boardwalk. Up to 27 feet of the existing beach width was impacted, with the greatest displacement occurring near the new bridge. This paper describes the wave environment and coastal processes at Niantic Bay, the design of scour protection for a railroad embankment retaining wall, the design of a restored beach and the design of a terminal groin/jetty at the mouth of the Niantic River.

Structural and functional aspects of berm breakwaters have been covered in earlier papers by the present authors and with geometrical design rules for berm breakwaters presented at ICCE 2014, this paper mainly focuses on design aspects related to armourstone, armourstone grading, quarrying for armourstone, and construction aspects of berm breakwaters, especially where these aspects differ from conventional rubble mound structures.

This paper presents the results of a systematic validation of numerical simulation of reflection and transmission of rubble-mound breakwater structures. The aim of the study is to provide a body of validation measurements for increasingly complex situations, starting simple and building up the complexity in terms of breakwater geometry, wave conditions, and numerical simulation models. The predictions from a set of three different numerical models were compared against measurements from small scale physical model tests. The results of the comparison and the achieved level of accuracy are reported. Finally, a hypothetical application for the design of rubble-mound breakwaters is presented.

A new and symmetrical single layer armour unit, the crablock, has been designed in the U.A.E. One breakwater was reconstructed with crablock, but very limited testing had been performed. Just to become more acquainted with this new unit, pre-competitive research at a university has been performed, which is the subject of this paper. Being a new armour unit, the placement was investigated first. Then physical model tests were performed in a wave flume to come up with results on stability and wave overtopping. Moreover, to determine the interlocking properties of armour units, pull tests were also conducted in this research. Those results are not part of this paper. Test results on stability showed that the longer waves affected the armour layer a little more, with larger movements and earlier displacements. Packing density as well as placement pattern showed no influence on wave overtopping. The overtopping tests gave larger overtopping than expected, which might be due to the fairly steep 1:30 foreshore.

The concrete-enhanced synthetic turf (CEST) revetment system is an innovative technology suited for use protecting coastal structures. It provides an aesthetically pleasing hardened revetment with exceptional armoring and hydraulic performance. This paper introduces the innovative technology of CEST revetment systems, and describes their performance and potential use for protecting coastal structures. This performance includes the results of an extensive full-scale testing program which has been successfully completed at Colorado State University–Engineering Research Center (CSU). The testing included steady-state overtopping, hydraulic jump, unsteady wave overtopping, large debris evaluation, and intentional damage to the system (pulverize infill and puncture holes). Lastly, example installations of the CEST system are presented in the paper.

Since 1977 dedicated studies are made to the stability of rubble mound break-water toes under wave attack. A large number of stability methods is available, but prediction accuracy is low and validity ranges are too small for use in practice. In this research the decoupled model approach is used to evaluate prediction capacity of existing toe stability methods. The approach uses numerical model IH-2VOF for a prediction of stability. Review of the model showed that it is highly sensitive to stone properties and that turbulence was not modelled. Under the assumption that the latter is not of major importance, calibration of motion formulae against physical measurements and evaluation of the stability methods was performed. The decoupled model approach appeared to give good stability predictions. Validity limits of the stability methods seemed to be too strict. A ranking of stability methods was made. Future validation should confirm the results before incorporation in design manuals.

The objective of this paper is to evaluate damage in breakwaters armoured with tetrapods using physical modelling data. The hydraulic laboratory tests reproduced the complex geometry of a rubble mound breakwater armoured with tetrapod concrete blocks and subjected to breaking wave action. The test programme included both flume (2-dimentional; 2D) tests and wave basin (3-dimentional; 3D) tests using several combinations of input parameters, such as wave heights, wave periods, and wave directions, water level elevations, and tetrapod sizes. During physical model tests, the hydraulic stability of the tetrapod-armoured breakwater was evaluated, and the damage was measured for every design storm segment using the ‘flickering’ technique. The results obtained from the laboratory tests are in general similar to those predicted using published literature regarding the stability coefficient (K_D) of Hudson’s formula.