Storm Surge Barrier Research Articles

An integral approach to design the Roggenplaat intertidal shoal nourishment

The Eastern Scheldt, a tidal basin in the southwest of The Netherlands, underwent large physical and ecological changes due to a system-wide human interference. The construction of a storm surge barrier at the seaward side and closure of the upstream branches in the 1980s resulted in intertidal flat erosion. This has far reaching consequences for the ecological functioning of these habitats, especially as foraging ground for many wader species. Therefore, a 1.3 million m3 sand nourishment is foreseen on the Roggenplaat intertidal shoal to mitigate the erosion and preserve suitable foraging habitat for waders for the coming 25 years. This paper presents an integral nourishment design approach. It consists of the following steps: (i) understanding the morphology and ecology, (ii) translation of the nourishment objective into an evaluation framework, (iii) construction of a suitability map indicating potential nourishment locations, (iv) generation of nourishment designs, (v) short-term morphodynamic numerical model simulations, (vi) estimation of the long-term shoal development using a simplified approach, (vii) integral evaluation leading to the preferred design. This integral approach resulted in a design that is expected to fulfill the Roggenplaat nourishment objective, accounting for ecological, morphological, economical and technical aspects. This integrated approach could form a basis for future intertidal shoal nourishment designs worldwide.

Effect of Venting Holes to Relieve Wave Impact Pressures on Flood Gates with Overhangs

Flood gates in storm surge barriers or outlet sluices can be prone to violent wave impacts. When an obstruction is present at the sea side above the gate, confinement of the incoming waves can lead to impulsive wave loads, even when the waves are non-breaking. The large loads can increase the stresses in the gate and structure considerably. One of the measures that is often discussed to relieve the pressures of these impacts is to apply small openings in the gates. In this paper the potential effect of these venting holes on the wave impact loads is determined. The decrease in impact pressure impulse is determined for a range of venting hole geometries is determined by numerical 2D and 3D solutions of a schematized wave impact. In this model the pressure impulse P (integral of the local pressure over the small impact duration) is determined directly by the so-called pressure impulse theory. The potential decrease in pressure impulse due to wave impacts is presented. Moreover, some initial CFD modelling is applied, and the applicability of the pressure impulse theory is discussed.

Liquefaction flow slides in large flumes

Liquefaction flow slides in sand have been investigated during an extensive experimental research programme during the period 1973–1977 on behalf of the design of the storm surge barrier in the Oosterschelde estuary. The programme included more than a hundred tests in large- and medium-sized flumes on submerged, loosely packed sand bodies. Each sand body had a horizontal surface and a very steep, supported slope as initial boundaries. Retrogressing liquefaction flow slides with high retrogression velocity and large retrogression distance occurred in several tests with very loosely packed sand. Retrogression velocities and distances in the other tests were just a fraction of those in first mentioned tests, although liquefaction occurred in some of them. The test set-up, measurements and results of the tests are described in this paper. An interpretation of the liquefaction flow slide process as a sequence of several interacting sub-processes is presented as well. Finally, tentative scaling rules are given and compared with observations.

Observations and Analysis of the Horizontal Structure of a Tidal Jet at Deep Scour Holes

Scour in the vicinity of a hydraulic structure may compromise its geotechnical stability or that of nearby structures. Much fundamental research has been dedicated to the understanding and prediction of these processes, in order to enable the efficient design of mitigation measures. While most of these efforts consider laterally uniform flows, nonuniformity is the rule rather than the exception. This study presents field observations near the storm surge barrier in the Eastern Scheldt estuary, The Netherlands, where significant scour holes have developed. The tidal flow through this semi‐open barrier exhibits characteristics of a shallow jet. A pronounced contraction of this jet toward the nearby scour hole during particular stages of the tidal cycle is revealed, attributed to potential vorticity conservation; the depth‐averaged vertical vorticity increases proportionally to the depth increase. Measurements show a vertically uniform velocity profile in the scour hole that is attributed to a reduction of the adverse pressure gradient due to the contraction, that suppresses boundary layer separation from the upstream slope of the scour hole. A positive feedback mechanism is thus revealed; lateral velocity gradients lead to relatively high near‐bed velocities in the scour hole which enhances erosion—causing an even stronger horizontal contraction—maintaining the scouring potential. If the upstream flow field is laterally uniform (observed around slack tide), horizontal contraction does not occur, and the boundary layer separates from the upstream slope. The scour depth will then tend to an equilibrium. The results infer the importance of the nonuniformity of the horizontal flow field.

Entrapment of an estuarine fish associated with a coastal surge barrier can increase the risk of mass mortalities

Estuarine storm surge barriers are designed to prevent the flooding of human-developed landscapes. While such barriers may have a range of ecological impacts, including the fragmentation of aquatic habitats and the alteration of water quality, their impact on obligate estuarine fishes is largely unknown. The sparid, Acanthopagrus butcheri, was used as a model species to determine how surge barriers may influence the movements of solely estuarine species and fish kill events. Individual A. butcheri were monitored for one year using passive acoustic telemetry in the Vasse-Wonnerup Estuary (south-western Australia), in which fish kills occur regularly during summer and autumn. Hydrological data and surge barrier operational information were used to make inferences on the movements and habitat use of A. butcheri. Individuals were largely restricted to the waters downstream of the surge barriers. The fish tended to occupy deeper sites in proximity to complex structure with the distribution also influenced by changes in salinity during the spawning period. A strong seasonal trend existed in the daily distance travelled by the fish and this was positively associated with the annual flow period. The majority of fish that successfully passed upstream through one of the surge barriers did so through a fishgate that operated outside of the spawning period. All those fish were then likely trapped with no downstream fish passage occurring in summer and autumn at a time when water quality was characterised by low dissolved oxygen and cyanobacterial blooms. The surge barrier therefore acts as a seasonal trap and increases the risk of mass mortalities. Given a projected increased need to combat flooding and storm surges associated with climate change in low-lying coastal areas, the study highlights the necessity of ensuring that the life-cycles and movement requirements of estuarine fishes are considered in the design and operation of coastal flood mitigation structures.

A life cycle costing approach for discounting in age and interval replacement optimisation models for civil infrastructure assets

Civil infrastructure assets, such as roads, locks, bridges, treatment plants and storm surge barriers, are often characterised by long service lives and corresponding technical life cycles. When life cycles are long, the time value of money plays a role in asset management decision-making on capital investments and operation and maintenance expenditures. In this paper, a new life cycle costing (LCC) approach for discounting in two classes of maintenance optimisation models is developed. These models are the age replacement model and the interval replacement model. Three well-known LCC techniques, which are the present worth, the capital recovery and the capitalised equivalent worth, are combined and used to develop a stepwise methodology. This methodology is validated with the few case-specific mathematical equations that exist in the literature. The advantage of using this alternative LCC approach is its applicability and flexibility for reliability and maintenance engineers. The resulting LCC method builds on well-known LCC formula and enhances the understanding of the inclusion of discounting principles in reliability models. Understanding these principles makes the method flexible. Practitioners can extend or adapt the method to changing circumstances, such as additional cash flows and altering reliability modelling.

Modeling the Hydrodynamic Performance of a Conceptual Storm Surge Barrier System for the Galveston Bay Region

Modeling the Hydrodynamic Performance of a Conceptual Storm Surge Barrier System for the Galveston Bay Region

Overview and Design Considerations of Storm Surge Barriers

The risk of flooding in coastal zones is expected to increase due to sea level rise and economic development. In larger bays, estuaries, and coastal waterways, storm surge barriers can be constructed to temporarily close off these systems during storm surges to provide coastal flood protection. Worldwide, 18 storm surge barriers have been constructed thus far, but they are increasingly being considered as a future solution for other coastal locations. This study provides a systematic overview of existing storm surge barriers. It analyzes information about the main functions of each barrier, the type of gates used, and the associated costs. It also shows that functional requirements determine the design and layout of the barrier. The main design challenges are discussed. The study results may be of use in future planning and preliminary storm surge barrier design

Hydraulic Experiments on Sinkable Floating Storm Surge Barrier under Various Wave Actions

ABSTRACT Shim, J.-S., Min, I.-K., and Yoon, J.-J., 2017. Hydraulic experiments on sinkable floating storm surge barrier under various wave actions. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 184–188. Coconut Creek (Florida), ISSN 0749-0208. A sinkable floating storm surge barrier is a new type of structure designed to reduce coastal disasters from storm surges. This barrier usually lies on the seabed, but its buoyancy allows it to rise up as a seawall when a storm surge occurs. A sinkable floating-type storm surge barrier consists of a buoyant main body connected to a foundation structure on the seabed by a hinge. In this study, the wave forces acting on the barrier were experimentally investigated. To evaluate the wave reflection and transmission from this buoyant floating-type storm surge barrier, hydraulic experiments were performed under regular and irregular wave conditio...

The differences in morphological development between the intertidal flats of the Eastern and Western Scheldt

Human interventions have a large impact on estuarine morphology. The intertidal flats in the Eastern Scheldt and Western Scheldt estuaries (The Netherlands) have faced substantial morphological changes over the past decades. These changes are thought to be caused by human interventions, such as the construction of the storm surge barrier in the mouth of the Eastern Scheldt, and the deepening of the navigation channels of the Western Scheldt. This paper analyses several datasets and numerical simulations of hydrodynamics, providing an overview of the various morphological characteristics of the intertidal flats in the two estuaries over time and space. Apart from the volume, area and average height of these areas, also the integral steepness of each flat is quantified based on its full geometry. The analyses focus on the intertidal flats surrounded by water, which allows for a robust comparison between the different flats. The intertidal flats in the Western Scheldt appear to be substantially steeper compared to those in the Eastern Scheldt. The data indicates that a larger average height of a flat is related to a larger steepness. Despite variations in the evolution of the different flats, distinct characteristics of both estuaries are observed. An opposed trend is identified over time: the flats in the Western Scheldt have mainly increased in height, whereas the flats in the Eastern Scheldt have lowered after the completion of the storm surge barrier. This opposing development is associated with differences in tidal flow velocities in the estuaries, which are the result of human interventions.

Between conflict and consensus: Searching for an ethical compromise in planning

To resolve conflicts and disagreements in planning, a compromise is often necessary. Where immediate consensus is unlikely and where antagonistic conflicts can lead to worse outcomes, a compromise is especially valued. Yet a compromise is also likely the least desired resolution, except for failure to reach a resolution. In this way, a compromise educes a mixed morality: A compromise has to presume some cooperative goodwill, yet forging a compromise often means violating important principles or abandoning some desired goods. If planners compromise, then this compromise ought to be an ethical one. But what is an ethical compromise in planning? In this article, we examine three cases of planning conflict: namely, the case of the Storm Surge Barriers in the Eastern Scheldt, the Netherlands; the case of the Cross Island Line in Singapore; and, finally, the case of the Calamity Polders, the Netherlands. Through these case studies, we draw out and illustrate three different ideal types of compromises important to planning and further describe the practical and ethical implications of a compromise.

Economic optimization of coastal flood defense systems

Coastal flood defense systems can consist of multiple lines of defense. In case of a system with a front and a rear defense (e.g. a storm surge barrier and levees), the front defense can improve the reliability of the rear defense by reducing the load on this rear defense. This paper develops a framework in order to assess whether including the influence of such a load reduction influences the economically optimal safety targets of both defenses. The economic optimization is carried out using two approaches: a simplified method developed to explore the behavior of the economic optimization with a front and rear defense, and a numerical framework geared towards practical applications. The numerical framework provides more flexibility in defining risk, cost and damage functions, and emphasizes on the applicability and tractability of the necessary steps from an engineering perspective. Both approaches are used in a hypothetical case study in order to quantify the effect of including a load reduction on the economically optimal safety targets. The results indicate that if a front defense can create a significant risk reduction in a cost efficient manner, more efficient economically optimal safety targets can be found by including the load reduction.

A modeling approach to assess coastal management effects on benthic habitat quality: A case study on coastal defense and navigability

The natural coastal hydrodynamics and morphology worldwide is altered by human interventions such as embankments, shipping and dredging, which may have consequences for ecosystem functionality. To ensure long-term ecological sustainability, requires capability to predict long-term large-scale ecological effects of altered hydromorphology. As empirical data sets at relevant scales are missing, there is need for integrating ecological modeling with physical modeling. This paper presents a case study showing the long-term, large-scale macrozoobenthic community response to two contrasting human alterations of the hydromorphological habitat: deepening of estuarine channels to enhance navigability (Westerschelde) vs. realization of a storm surge barrier to enhance coastal safety (Oosterschelde). A multidisciplinary integration of empirical data and modeling of estuarine morphology, hydrodynamics and benthic ecology was used to reconstruct the hydrological evolution and resulting long-term (50 years) large-scale ecological trends for both estuaries over the last. Our model indicated that hydrodynamic alterations following the deepening of the Westerschelde had negative implications for benthic life, while the realization of the Oosterschelde storm surge barriers had mixed and habitat-dependent responses, that also include unexpected improvement of environmental quality. Our analysis illustrates long-term trends in the natural community caused by opposing management strategies. The divergent human pressures on the Oosterschelde and Westerschelde are examples of what could happen in a near future for many global coastal ecosystems. The comparative analysis of the two basins is a valuable source of information to understand (and communicate) the future ecological consequences of human coastal development.

Modeling Coastal Vulnerability through Space and Time

Coastal ecosystems experience a wide range of stressors including wave forces, storm surge, sea-level rise, and anthropogenic modification and are thus vulnerable to erosion. Urban coastal ecosystems are especially important due to the large populations these limited ecosystems serve. However, few studies have addressed the issue of urban coastal vulnerability at the landscape scale with spatial data that are finely resolved. The purpose of this study was to model and map coastal vulnerability and the role of natural habitats in reducing vulnerability in Jamaica Bay, New York, in terms of nine coastal vulnerability metrics (relief, wave exposure, geomorphology, natural habitats, exposure, exposure with no habitat, habitat role, erodible shoreline, and surge) under past (1609), current (2015), and future (2080) scenarios using InVEST 3.2.0. We analyzed vulnerability results both spatially and across all time periods, by stakeholder (ownership) and by distance to damage from Hurricane Sandy. We found significant differences in vulnerability metrics between past, current and future scenarios for all nine metrics except relief and wave exposure. The marsh islands in the center of the bay are currently vulnerable. In the future, these islands will likely be inundated, placing additional areas of the shoreline increasingly at risk. Significant differences in vulnerability exist between stakeholders; the Breezy Point Cooperative and Gateway National Recreation Area had the largest erodible shoreline segments. Significant correlations exist for all vulnerability (exposure/surge) and storm damage combinations except for exposure and distance to artificial debris. Coastal protective features, ranging from storm surge barriers and levees to natural features (e.g. wetlands), have been promoted to decrease future flood risk to communities in coastal areas around the world. Our methods of combining coastal vulnerability results with additional data and across multiple time periods have considerable potential to provide valuable predictions that resource managers can effectively use to identify areas for restoration and protection.

A Numerical Modeling Approach to Predict the Effect of a Storm Surge Barrier on Hydrodynamics and Long-Term Transport Processes in a Partially Mixed Estuary

Floodgates or storm surge barriers are increasingly being considered as feasible climate change adaptation strategies to mitigate flooding risk. We developed a numerical modeling approach for a partially mixed estuary to simulate long-term alterations to hydrodynamics and transport processes induced from human modifications; two types of partially embanked storm surge barriers across the mouth of Chesapeake Bay were examined. Under modeled scenarios, surge barriers exerted a significant influence on the tide, salinity, residual current, and transport processes. The surge barrier caused (1) a reduction of tidal range inside the estuary, (2) stronger stratification and further salt intrusion, weaker vertical mixing and larger vertical exchange time, and (3) a decrease of bottom inflow in the mainstem and weakened horizontal water exchange. The change of horizontal water exchange and residence time was not a linear response with the barrier size and it varied at different regions of the estuary. The modeling approach is suitable to assess large-scale long-term ecosystem changes induced by human modifications or adaptations under a changing system.

Management options for restoring estuarine dynamics and implications for ecosystems: A quantitative approach for the Southwest Delta in the Netherlands

The Delta Works, a series of dams and barriers constructed in the 1960's–1980's changed the estuarine landscape of the Rhine-Meuse-Scheldt delta (SW Netherlands) into more stagnant and disengaged freshwater, brackish water or saltwater lakes. The remaining tidal systems were adapted by building a storm surge barrier in the Oosterschelde and dike reinforcement works along the Westerschelde. The Delta Works brought protection against flooding, but at the same time resulted in environmental and socio-economic problems, such as degradation of ecological quality and ecosystem functioning, disruption of fish migration routes, water and sediment quality problems.In this study we explore in an integrated, quantitative way the consequences of a number of management options for the Southwest Delta and their implications for the occurrence and distribution of aquatic and estuarine habitats, considering the mutual coherence between the water basins. Five scenarios were evaluated using a 1D hydraulic, water quality and primary production numerical model and GIS habitat mapping. Scenarios vary from small-scale interventions, such as changes in day-to-day management of hydraulic infrastructures or creation of small inlets in dams, feasible in the short term, to restoration of an open delta by removing dams and barriers, as a long term potential. We evaluate the outcomes in relation to the restoration of estuarine dynamics, as this is in policy plans proposed as a generic solution for the current ecological and environmental problems. Net water flow rates show more complex patterns when connectivity between water basins is increased and when sluice management is less strict. Estuarine transition zones and fish migration routes are partly restored, but only fully develop when basins are in open connection with each other. Area of intertidal habitats, tidal flats and tidal marshes, increases in each scenario, ranging between 7 and 83%, 1–56%, and 8–100% respectively, depending on scenario. Large scale infrastructural adaptations are needed to restore estuarine dynamics at large scale.The use of a 1D numerical model allowed to quantify the effect of different management measures for all water basins simultaneously, but also has its limitations. The model does not resolve more complex processes such as vertical mixing and morphodynamic changes. This requires expert judgment and more detailed 3D modelling.

Application of data assimilation for improved operational water level forecasting on the northwest European shelf and North Sea

For the Netherlands, accurate water level forecasting in the coastal region is crucial, since large areas of the land lie below sea level. During storm surges, detailed and timely water level forecasts provided by an operational storm surge forecasting system are necessary to support, for example, the decision to close the movable storm surge barriers in the Eastern Scheldt and the Rotterdam Waterway. In the past years, a new generation operational tide-surge model (Dutch Continental Shelf Model version 6) has been developed covering the northwest European continental shelf. In a previous study, a large effort has been put in representing relevant physical phenomena in this process model as well as reducing parameter uncertainty over a wide area. While this has resulted in very accurate water level representation (root-mean-square error (RMSE) ∼7–8 cm), during severe storm surges, the errors in the meteorological model forcing are generally non-negligible and can cause forecast errors of several decimetres. By integrating operationally available observational data in the forecast model by means of real-time data assimilation, the errors in the meteorological forcing are prevented from propagating to the hydrodynamic tide-surge model forecasts. This paper discusses the development of a computationally efficient steady-state Kalman filter to enhance the predictive quality for the shorter lead times by improving the system state at the start of the forecast. Besides evaluating the model quality against shelf-wide tide gauge observations for a year-long hindcast simulation, the predictive value of the Kalman filter is determined by comparing the forecast quality for various lead time intervals against the model without a steady-state Kalman filter. This shows that, even though the process model has a water level representation that is substantially better than that of other comparable operational models of this scale, substantial improvements in predictive quality in the first few hours are possible in an actual operational setting.

Characterizing the hydraulic interactions of hurricane storm surge and rainfall–runoff for the Houston–Galveston region

Planning of traditional coastal flood risk management strategies are largely predicated on storm surge protection against extreme hurricanes, i.e. storm surge. However, (1) hurricane storm surge and (2) hurricane rainfall–runoff are not mutually exclusive flood hazards. Little research has emphasized the need for quantifying and characterizing the joint hydraulic processes between hurricane storm surge and rainfall–runoff during real events for enhancing effective flood risk mitigation. In this regard, an improved hydrological and hydrodynamic modeling framework has been developed for the Houston Ship Channel (HSC) and Galveston Bay to serve as a quantitative testbed for evaluating coupled hurricane storm surge and rainfall–runoff. Modularity within the modeling framework allows for landfall shifting of historical hurricane tracks, wind fields, and corresponding rainfall patterns to serve as numerical model inputs, as well as providing an expanded dataset of storm events. Distributed hydrologic and unsteady hydraulic analyses of upstream rainfall–runoff and storm surge are conducted for hurricanes Katrina (2005), Ike (2008), and Isaac (2012) under three synthetically shifted landfall locations near the HSC and Galveston Bay regions. For the modeled scenarios, results show that peak flows from storm surge easily dominate those of rainfall–runoff, but that rainfall–runoff can constitute more than half of the total flood volume draining towards the HSC. Most modeled scenarios reveal less than 24h of separation between peak surge and peak rainfall–runoff. In the same way that storm surge is sensitive to hurricane landfall location and angle of approach, so are spatial rainfall distributions and associated inland runoff processes, due to wide topological variations in coastal watershed boundaries. Analysis of coastal flood mitigation is extended with the dynamic modeling of a proposed storm surge barrier system at the HSC, with its performance quantified under the given hurricanes. The surge barrier system is demonstrated to be hydraulically feasible for all scenarios, with maximum water surface elevation reductions ranging between 0.63m and 3.28m. However, accurate storm surge and riverine flood forecasting methods will be critical for achieving optimal gate and barrier operations.

Evaluation of a tidal flat sediment nourishment as estuarine management measure

The tidal flats in the Eastern Scheldt tidal basin (The Netherlands) are eroding as a result of the construction of the storm surge barrier. These intertidal areas are important foraging grounds for birds and therefore it is important to mitigate the negative effects of erosion. As a pilot, a small part (20 ha) of the Galgeplaat tidal flat in the middle of the Eastern Scheldt was nourished with 130,000 m3 of sediment in 2008. This paper investigates this tidal flat nourishment using a large set of morphological and ecological monitoring data from 2008 to 2012. The nourishment proved effective in mitigating the negative effects of tidal flat erosion. The elevated tidal flat provides a foraging area for birds that is available for a longer period. The nourished area was relatively stable, giving time for the recovery of benthic macrofauna such that birds can benefit from the longer exposure time. Therefore, we conclude that sediment nourishments are an effective management measure to counteract the negative consequences of tidal flat erosion in the Eastern Scheldt, and have potential for other estuaries worldwide.

CLIMATE CHANGE ADAPTATION IN TOKYO BAY: THE CASE FOR A STORM SURGE BARRIER

Increases in typhoon intensity and sea level rise could pose significant challenges to coastal defences around Tokyo Bay. In order to analyse the extent of future problems the authors determined the increase storm surge that could result from an increase in typhoon intensity and sea level rise to this area around the turn of the 21st century. Results show how the various settlements around Tokyo Bay are at considerable risk of storm surges and sea level rise in the future. If defences are breached the potential direct economic consequences could be significant, potentially in excess of 100 trillion yen, with the indirect costs likely to be even greater. As a result it is likely that sea defences will have to be strengthened around Tokyo Bay in the future, which could cost in the order of 370bn yen to defend against a 1 in 100 year storm by the year 2100. Alternatively, a storm surge barrier could be built, which would be more expensive (possibly in the range of 700-800bn yen), though it could increase the protection level and would be able to cope with 1 in 200 or 500 year events, amongst other benefits.