Storm Surge Barrier Research Articles

Response of estuarine morphology to storm surge barriers, closure dams and sea level rise

Storm surge barriers and closure dams influence estuarine morphology. Minimizing consequential ecological impacts requires a thorough understanding of the morphological adaptation mechanisms and associated time scales. Both are unraveled using three decades of morphological measurements on the adaptation of the Eastern Scheldt estuary (The Netherlands) to a storm surge barrier and closure dams. Both the storm surge barrier (through a decrease in cross-sectional area) and closure dams (inducing a reduction in surface area of the estuary) contributed to a reduction in tidal prism. As a smaller tidal prism implies a smaller equilibrium volume of the channels, the channels demand sediment to adjust. Consequently, by providing sediment to the channels, the intertidal flats erode. Erosion rates decreased while the sediment demand of the channels attenuated. This attenuation in sediment demand resulted mainly from tidal prism gains, caused by intertidal flat erosion and sea level rise. Erosion rates of the intertidal flats decreased further while they flattened to adapt to the reduced tidal velocities. Furthermore, storms caused erosion events, after which the long-term adaptation pace of intertidal flats suddenly reduced. Despite decreasing erosion, sea level rise enhances the drowning of intertidal flats in sediment-scarce estuarine systems, thereby pressuring these estuarine ecosystems and raising the need for mitigation measures.

Asset management for storm surge barriers: how and why?

Due to increasing flood risks, storm surge barriers become crucial for the socioeconomic continuity of coastal areas. They provide flood protection, especially against extreme events, by operating under specific circumstances. This imposes high-performance requirements for storm surge barriers and their asset management during their lifetime and emphasises the role and criticality of their asset management. For this purpose, the research investigates asset management for storm surge barriers by focusing on the approach in the Netherlands and analysing it relative to distinctive characteristics of storm surge barriers. Based on thematic analysis, the study unfolds that barriers’ characteristics: (1) clarify the vital motives for the asset management approach, (2) confront the approach with challenging conditions, resulting in further maturation of the approach, and (3) require ongoing support from the approach, enforcing continuous improvement and resilience of the asset management approach. These findings demonstrate the strong influence of barriers’ characteristics on their asset management approach and provide a fundamental understanding of asset management for storm surge barriers. This supports flood defence authorities in the development and improvement of asset management for storm surge barriers and underpins associated complexities for future designs and research. Furthermore, the study assists in tailoring approaches for other assets.

Intergenerational transfer of engineering expertise: knowledge continuity management in storm surge barrier engineering

PurposeEngineering knowledge continuity is crucial for the life cycle management of long-lived and complex assets, such as nuclear plants, locks and storm surge barriers. At the storm surge barriers in the Netherlands, engineering knowledge continuity is not yet fully assured, despite long-standing efforts. This study aims to explore the relationship between system characteristics, the organizational demarcation of maintenance and operation and the challenges in achieving engineering knowledge continuity and provides suggestions for improvement of theory and policy.Design/methodology/approachTen semi-structured interviews were conducted with professionals from various backgrounds in construction, engineering and asset management of the Dutch storm surge barriers, augmented with visits to barriers and barrier teams. A thematic analysis was used to identify and describe the challenges to engineering continuity, their origins and potential solutions. We reviewed knowledge management policy documents and asset management consultancy reports to validate the findings. Additionally, we engaged in frequent interactions with professionals at the barriers. We achieved saturation and validation once no new issues were raised during these discussions.FindingsThe thematic analysis developed multiple themes describing the challenges to engineering continuity, their origins and potential solutions. The key findings are that expert engineers are critically important to deal with redesigns induced by obsolescence. Moreover, due to barrier uniqueness, long redesign cycles and reliability requirements, conventional knowledge continuity tools are insufficient to enable new engineers to reach expert level. Finally, the thematic analysis shows that, in some cases, outsourcing should be reduced to facilitate internal learning.Originality/valueThe study introduces the application of the knowledge-based view of the firm and the concept of requisite knowledge redundancy to the long-term management of complex assets. It calls for more attention to long gaps in the use of unique knowledge and the effect on knowledge continuity.

Spatial and temporal variability of water transparency, its primary drivers, and other optical properties in the Hudson River Estuary

Water transparency, measured as the diffuse attenuation coefficient of photosynthetically-active (400–700 nm) radiation, KdPAR, was measured monthly from May–Oct 2020 at 73 locations along 250 km of the Hudson River estuary (HRE) between New York City, NY and Waterford, NY. Three primary optical drivers of KdPAR variability: chlorophyll concentration (CHL), turbidity, and light absorption by colored dissolved organic matter (aCDOM), were measured concurrently to assess their relative importance to spatial and temporal KdPAR patterns. KdPAR was higher and more variable in the brackish HRE relative to limnetic regions further north. KdPAR was also significantly higher nearshore and near sewage treatment plant outfalls relative to midchannel sites. Temporal variability at individual stations was generally lower than cross-channel or cross-region spatial variability. Turbidity was the most important factor in KdPAR variability in all regions of the HRE, followed by CHL, with aCDOM playing a lesser role. Although many water quality variables have changed in the HRE over recent decades, KdPAR measurements in the brackish regions overlapped with published observations from the 1970s–1990s. KdPAR in the limnetic regions was lower in 2020 than measurements made prior to the Zebra mussel invasion in the early 1990s, but similar to measurements in the limnetic regions made since the invasion. Results of this study can be used to optimize satellite-based remote sensing algorithms for synoptic water quality observations of the HRE. Proposed future alterations in the HRE, including dredging and the construction of storm-surge barriers, would likely change existing KdPAR patterns. This study therefore provides an updated baseline for optical parameters in the HRE and highlights the importance of understanding the impacts of any proposed alterations to upper-water-column turbidity in this system. Results also demonstrate that KdPAR, euphotic depths, and Secchi depth measurements were positively correlated throughout the HRE. Secchi depth measurements may therefore be useful for additional retrospective studies, and future monitoring (including by satellite-derived KdPAR) of water transparency in the HRE.

Large-Scale Levee Breach Experiments With Foreshores

Coastal flood risk is expected to increase substantially in the near future. Main drivers are climate induced sea level rise, increased storm surge and land subsidence. Meanwhile, land subsidence compounds to increased extreme water levels as more land is susceptible to flooding. Without coastal defense or adaptation 50% more people are exposed to flooding than present day (Kireczi et al., 2020). Coastal regions are currently primarily protected by hard (grey) flood defenses such as storm surge barriers, seawall, dikes and dunes. Periodically, strengthening of these grey structures is necessary to comply with current or updated safety standards. For dikes, conventional strengthening methods are crest heightening or (base) widening. However, these methods have structural and financial limits. Instead, more sustainable methods are explored in which nature also plays a larger role. These solutions are known as Nature based Solutions (NbS). For flood protection, tidal marshes have gained great interest as a Nature based Solution in the past two decades. Tidal marshes provide a lot of ecosystem services (Barbier et al., 2011). One such service is flood protection, attributed to wave attenuation (Vuik et al, 2016). A secondary effect is flood impact reduction (Zhu et al., 2020) due to the high elevation of tidal marshes limiting the inflow to the breach. Secondly, the tidal marsh can act as a sill in front of the breach when water levels drop below the tidal marsh level. To quantify the effect of tidal marshes on flood impact the breaching process in combination with a tidal marsh (or foreshore in general) needs to be understood. In this study we performed a large-scale physical dike experiment where we breached a dike seven times. Three tests are done without a sediment layer in front of the dike (no foreshore), two with a sandy layer (sandy beach) and two with a clay layer (tidal marsh without vegetation). From the experiments we gain insight into differences in the dike breaching process with and without an erodible sediment layer in front of the dike

Insights on the Extreme Storm Surge Event of the 22 November 2022 in the Venice Lagoon

The Italian Institute for Environmental Protection and Research (ISPRA) manages the national sea state real time monitoring system for Italy, which consists of the National Sea Level Network (RMN), the North Adriatic and Venice Lagoon Sea Level Network (RMLV), the National Wave Networks (RON), and a marine weather forecasting system. These systems are particularly deployed to monitor and predict storm surges that affect the northern part of the Adriatic Sea and the Venice Lagoon, usually causing damages and morphological impacts over the highly anthropized coastal areas. On 22 November 2022, an extreme storm surge event occurred in the northern Adriatic Sea, producing severe damages on its coastline. Venice and the surrounding urban settlements have been protected from flooding thanks to the operation of the Mo.S.E. (Modulo Sperimentale Elettromeccanico) system, a set of artificial barriers built to isolate the lagoon from the sea in case of extreme high tides. Coastal flooding prevention measures, such as storm-surge barriers, are indeed being widely adopted globally because of the accelerating rise in sea levels. An analysis of this extreme event is presented here to highlight the functionality and the usefulness of the ISPRA sea state monitoring system. In particular, the analysis of the as-if scenario reproducing the natural tide propagation within the lagoon, neglecting the operation of the Mo.S.E. system, can only be pursued by using hydrodynamic models forced using extensive observed data. Results highlight that the “not-regulated” sea level would have exceeded 200 cm above the reference datum at Chioggia, a threshold never recorded in the Venice Lagoon since sea level monitoring systems have been operational.

How should storm surge barrier maintenance strategies be changed in light of sea-level rise? A case study

Sea-level rise and changes in storminess, together with population growth and coastward migration, are increasing the risks of coastal flooding. The impacts are amplified in coastal cities due to the high concentration of inhabitants, infrastructure and services in low lying areas. Many coastal cities are located in estuaries, and storm surge barriers are often constructed to provide flood protection in these areas with long exposed coastlines. For these complex and unique structures, maintenance is vital to ensure they remain reliable and comply with legal protection standards. To ensure safe conditions for workers, storm surge barriers typically define water level thresholds, at which maintenance work must stop when these water levels are reached or exceeded. This paper evaluates the changes in past and future water levels exceeding the maintenance threshold to inform management, maintenance and operation strategies, and design, of storm surge barriers. The Maeslant barrier in Rotterdam, Netherlands is used as a case study to test this analysis. Water levels from measurements taken at the Hoek van Holland tide gauge are compared to the maintenance threshold level. The number of past threshold exceedances is determined and the sensitivity of exceedances to threshold level are assessed. Results show that the maintenance threshold has been exceeded 991 times of which 13% occurred during the maintenance season. Conversely, there were periods in the storm season when water levels were below the maintenance threshold and work could have been carried out safely. The effect of sea-level rise and natural inter-annual tidal cycles on future threshold exceedances is also assessed. Findings reveal that the maintenance window will shift earlier in the year and narrow until exceedances of the maintenance threshold occur regularly all year around. With 1 m sea-level rise maintenance threshold exceedances are likely to occur regularly all year around by 2048. This analysis highlights that maintenance strategies at the Maeslant barrier will need to be adapted for the barrier to remain operational until its design life of 2 100. This is due to the increase in maintenance threshold exceedances resulting from natural interannual tidal cycles combined with sea-level rise. This analysis framework is applicable to existing barriers worldwide to assess future intervention points and for barriers in the design phase to verify the implications of design decisions on planned maintenance.

Discount Rate Selection for Investments in Climate Change Adaptation and Flood Risk Reduction Projects

The selection of an appropriate discount rate is a critical yet often neglected aspect of valuing flood protection and climate adaptation projects. We examine current discounting practices in flood risk management and climate adaptation literature and compare these practices with a proposed fair market value (FMV) discounting approach, in which we discount project cash flows based on their levels of systematic market risk, consistent with practice in the private sector. Using publicly available data, we demonstrate minimal correlation between flood risk–related cash flows and overall market returns, suggesting flooding-related cash flows are most appropriately discounted near the risk-free rate. We consider the example of a proposed storm surge barrier in Boston Harbor and compare prevailing public-sector discounting approaches with this FMV approach. Our results suggest prevailing discounting approaches systematically undervalue flood risk reduction benefits and climate adaptation investments relative to the private-sector valuation implied via the FMV approach.

Assessment of the impact of tidal power extraction from the Eastern Scheldt storm surge barrier through the evaluation of a pilot plant

Hydraulic structures can be a promising place for tidal energy extraction due to the high flow velocities, easy access to the power grid and easy access for maintenance. However, quantification of the impacts of a tidal power plant in a hydraulic structure is not straight forward. In 2015 a pilot plant consisting of an array of five Tocardo tidal turbines was installed in the Eastern Scheldt Storm Surge Barrier in the Netherlands. This pilot was accompanied by monitoring studies to verify that the operation of the plant had no adverse impact on the barrier and its surroundings. This paper presents the assessment of the hydraulic impact of the tidal power plant in the storm surge barrier based on an analysis of water level and current measurements, combined with numerical modeling and followed by an assessment of the environmental impact with emphasis on the effects on the intertidal areas in the estuary. This validation approach by a pilot plant is imperative to understand the interaction between tidal turbines and the hydraulic structure on the local scale. This understanding gives extra credibility to the predictions of the extrapolated large-scale and large array assessments which will always be fully numerical.

Economic optimization of coastal flood defence systems including storm surge barrier closure reliability

AbstractStorm surge barriers are large movable hydraulic structures which close during a storm surge to prevent coastal floods. In the regions they protect, a failure to close the barrier is often the most likely cause for a catastrophic flood. Nevertheless, flood risk assessments usually only focus on raising flood defences behind the barrier. Despite its importance, there is no general method to assess the costs and benefits of improving the closure reliability. This paper presents a model that optimises investments considering both closure reliability improvements and raising flood defences behind the barrier, using the region protected by the Maeslant barrier as a case. We substantiate that constructing the Maeslant barrier was an optimal economic decision. Moreover, we demonstrate large investments such as a redundant barrier already being economically sound with a few decimetres of sea level rise. Based on our experience with this case study, we expect the model is useful in finding strategies to adapt to rising sea levels and other developments that cause coastal flood risk to rise worldwide.

Drivers of spatial and temporal micro- and mesozooplankton dynamics in an estuary under strong anthropogenic influences (The Eastern Scheldt, Netherlands)

The Eastern Scheldt estuary in the Netherlands has been anthropogenically changed by the construction of a storm surge barrier about 30 years ago, affecting abiotic conditions as well as phytoplankton and zooplankton (ZP). As the ZP communities have not been sampled in the last decades, it is unclear to what extent they have changed during the last 30 years. We analyzed the micro- and mesoZP composition and background parameters at eight stations in the Eastern Scheldt in spring, summer, and autumn 2018. Additionally, we conducted dilution experiments to estimate phytoplankton growth and microZP grazing rates. Seasonal variability of ZP was higher than spatial variability, but there were differences between stations. In agreement with data from the 1980s, we identified salinity and chlorophyll a as the most important factors in explaining the ZP community. Suspended particulate matter and water retention time were additionally identified for mesoZP, as well as dissolved inorganic nitrogen and phosphate concentration for microZP. We observed some changes in ZP composition with respect to the 1980s, most of which could be explained by the changes induced by the barrier construction. However, increased abundances of the cyclopoid copepod Oithona sp. were likely related to changes in phytoplankton composition due to large-scale bivalve cultivation in the estuary. Phytoplankton growth and microZP grazing rates were variable between seasons, which could be explained by changes in the phytoplankton community during the annual plankton succession. Overall, the observed alterations in the ZP community due to changed background parameters and intense bivalve filtration could affect the microbial loop as well as consumers of mesoZP and thus the functioning of the pelagic food web.

Assessment of exposure, coping and adaptation strategies for elements at risk to climate change-induced flooding in urban areas. The case of Jangwani Ward in Dar es Salaam City, Tanzania

Urban areas are the engines of socioeconomic growth and the homes of billions of people around the globe. In a changing climate, urban areas are inexorably from vulnerability to climate hazards including flooding which deters their social, economic, and environmental sustainability. The main objective of this paper was to explore exposure to elements at risk due to climate change-induced flooding in urban areas. In addition, the paper analyses the coping and adaptation strategies practiced at the community and national levels and recommends appropriate policy measures for enhanced climate resilience in urban areas. The study adopted purposeful sampling in which n = 95 households were selected for the study. Data collection methods involved household interviews with structured questionnaires, focused group discussions, documentary reviews, transect walks, surveys, and observations. Data analysis was done with a statistical package for social sciences. The results revealed that the elements at risk of exposure to climate change-induced flooding in the study area were physical infrastructures, socio-economic activities, livelihoods, and ecosystems. The study recommends enhancing resilience of elements at risk to climate change-induced flooding at national and local levels in urban areas. This is through promoting flood policies, strategies, laws, planning and management measures; enhance non-structural actions including flood forecasting, mapping, emergency evacuation plans and land use zoning and structural measures namely dams, dikes, storm surge barriers for adaptation to urban flooding.

Increased Utilization of Storm Surge Barriers: A Research Agenda on Estuary Impacts

AbstractRising coastal flood risk and recent disasters are driving interest in the construction of gated storm surge barriers worldwide, with current studies recommending barriers for at least 11 estuaries in the United States alone. Surge barriers partially block estuary‐ocean exchange with infrastructure across an estuary or its inlet and include gated areas that are closed only during flood events. They can alter the stratification and salt intrusion, change sedimentary systems, and curtail animal migration and ecosystem connectivity, with impacts growing larger with increasing gate closures. Existing barriers are being used with increasing frequency due to sea level rise. New barrier proposals typically come with maximum closure frequency recommendations, yet the future adherence to them is uncertain. Given that the broader environmental effects and coupled‐human dynamics of surge barriers are not well‐understood, we present an interdisciplinary research agenda for this increasingly prevalent modification to our coastal zone.

Effects of Storm Surge Barrier Closures on Estuary Saltwater Intrusion and Stratification

AbstractGated storm surge barriers have been constructed or proposed in many estuaries worldwide for coastal flood risk reduction. Past studies have shown that, even when open, a barrier system's fixed infrastructure can increase estuary stratification and salt intrusion, potentially affecting water quality and ecological processes. However, surge barrier closures could have a much stronger influence on estuary conditions by temporarily blocking the tidal exchange. In this project, we use an existing regional three‐dimensional hydrodynamic model, with modifications to simulate surge barrier closure and reopening, to study the effects on estuarine salt intrusion and stratification of the Hudson River. Across a range of modeled scenarios of gate closure frequencies, durations and river streamflows, we evaluate the changes caused by gate closures, as well as the recovery time to normal conditions. Our results for the Hudson show long‐duration gate closures (three or more days) with low streamflows temporarily lead to salt intrusion and stratification beyond recent historical extremes. Moreover, monthly frequency closures, which could occur as soon as 2070 under realistic scenarios of sea‐level rise and barrier management, do not allow for recovery under low streamflow conditions and could lead to durable changes to estuary physical conditions. As a result, long duration closures and high‐frequency closures both constitute a threat to municipal water supplies. This study demonstrates a framework for understanding the potential impacts of any proposed surge barrier system and can help improve our understanding of corresponding ecological impacts.

A framework for assessing the remaining life of storm surge barriers

Over the course of the last century, storm surge barriers have been built in several countries and proven to be successful in preventing flooding. However, the operation, reliability, and remaining life of these structures have come under increased pressure due to changing demands, intensified utilisation, and climate change. Yet, there is relatively little known about how these factors affect the remaining life of storm surge barriers. To address this issue, a framework is presented to assess the impacts of external drivers on the remaining life in a systematic manner. The framework considers both the technical state and functional performance and uses scenarios to evaluate the impact of external drivers. The application of the framework is demonstrated for the Hollandsche IJssel barrier (the Netherlands). The results indicate that sea level rise (SLR) is the dominant physical driver. Even in moderate SLR scenarios, the lifespan of the barrier may end in the 2040s if the functional performance with respect to flood protection and navigation cannot be improved. Ultimately, the study demonstrates how the remaining life of storm surge barriers could be assessed systematically and the impact of external drivers on the remaining life could be evaluated.

Changes in Estuarine Sediment Dynamics with a Storm Surge Barrier

Changes in Estuarine Sediment Dynamics with a Storm Surge Barrier

Coastal Defense Megaprojects in an Era of Sea-Level Rise: Politically Feasible Strategies or Army Corps Fantasies?

Storm surge barriers, levees, and other coastal flood defense megaprojects are currently being proposed as strategies to protect several US cities against coastal storms and rising sea levels. However, social conflict and other political factors add a layer of complexity that casts doubt on their status as practical climate adaptation options. The specific mechanisms responsible for some projects not progressing beyond initial planning stages remains unclear. In this study, we examined the outcome of two USACE storm surge barrier proposals to explore the political reasons why some coastal flood protection megaprojects break ground in the US, while others do not. Using original archive research, we concluded that storm surge barriers are politically challenging climate adaptation options because of modern environmental laws that provide avenues for expression of oppositional views within the decision process and the allure of alternative options that are more aesthetically pleasing and cheaper and faster to implement. To better allocate public resources and utilize the expertise of USACE, future flood protection megaprojects should first achieve broad support from the public, nongovernmental organizations (NGOs), and elected officials before beginning serious planning. This support could be achieved through new innovative designs that simultaneously address adverse environmental impacts and provide cobenefits (e.g., recreation). New designs should be studied to better understand the level of protection offered and their associated reliability so that USACE has confidence in their use.

Return periods of extreme sea levels: From magnitude to frequency, duration and seasonality. Implications in a regulated coastal lagoon

Extreme sea levels (ESLs) affect coastal ecosystems worldwide. Protection and adaptation strategies rely on the characterization of the extreme's occurrence probability in the future. However, knowledge on the occurrence rate and duration of ESLs is also needed to properly characterize the associated future risk. In this paper, we focus on the Venice lagoon, where a system of storm surge barriers can disconnect the lagoon from the sea to mitigate ESLs. Using long-term (96 years) sea level records, we model occurrence rate and duration of ESLs while accounting explicitly for seasonality and mean sea level rise. While historically ESLs occurred in the winter season, we project a significant increase (up to 10-fold with a mean sea level increase of +100 cm) of the occurrence rate also in the summer season, when disconnections from the sea can have profound impacts on the lagoon's ecosystem. We also predict an increase in ESLs durations up to 200 h, leading to longer disconnections of the lagoon from the sea in the future. Therefore, several adaptation strategies will be needed to limit the adverse effects of storm surge barriers on the lagoon ecosystem.

Effect of Mo.S.E. Closures on Wind Waves in the Venetian Lagoon: In Situ and Numerical Analyses

In the Venetian lagoon, the storm surge barriers (Mo.S.E. system) are crucial to prevent urban flooding during extreme stormy events. The inlet closures have some cascading effects on the hydrodynamics and sediment transports of this shallow tidal environment. The present study aims at investigating the effects of the Mo.S.E. closure on the wind-wave propagation inside the lagoon. In situ wave data were collected to establish a unique dataset of measurements recorded in front of San Marco square between July 2020 and December 2021, i.e., partially during the COVID-19 pandemic. Ten storm events were analyzed in terms of significant wave heights and simultaneous wind characteristics. This dataset allowed for validating a spectral wave model (SWAN) applied to the whole lagoon. The results show that the floodgate closures, which induce an artificial reduction of water levels, influence significant wave heights HS, which decrease on average by 22% compared to non-regulated conditions, but in the shallower areas (for example tidal flats and salt marshes), the predicted decrease is on average 48%. Consequently, the analysis suggests that the Mo.S.E. closures are expected to induce modifications in the wave overtopping, wave loads and lagoon morphodynamics.

Developing a framework for the assessment of current and future flood risk in Venice, Italy

Abstract. Flooding causes serious impacts on the old town of Venice, its residents, and its cultural heritage. Despite this existence-defining condition, limited scientific knowledge on flood risk of the old town of Venice is available to support decisions to mitigate existing and future flood impacts. Therefore, this study proposes a risk assessment framework to provide a methodical and flexible instrument for decision-making for flood risk management in Venice. We first use a state-of-the-art hydrodynamic urban model to identify the hazard characteristics inside the city of Venice. Exposure, vulnerability, and corresponding damage are then modeled by a multi-parametric, micro-scale damage model which is adapted to the specific context of Venice with its dense urban structure and high risk awareness. Furthermore, a set of individual protection scenarios are implemented to account for possible variability in flood preparedness of the residents. This developed risk assessment framework was tested for the flood event of 12 November 2019 and proved able to reproduce flood characteristics and resulting damage well. A scenario analysis based on a meteorological event like 12 November 2019 was conducted to derive flood damage estimates for the year 2060 for a set of sea level rise scenarios in combination with a (partially) functioning storm surge barrier, the Modulo Sperimentale Elettromeccanico (MOSE). The analysis suggests that a functioning MOSE barrier could prevent flood damage for the considered storm event and sea level scenarios almost entirely. A partially closed MOSE barrier (open Lido inlet) could reduce the damage by up to 34 % for optimistic sea level rise prognoses. However, damage could be 10 % to 600 % higher in 2060 compared to 2019 for a partial closure of the storm surge barrier, depending on different levels of individual protection.