Transmission of wave energy at permeable low crested structures

This paper presents a conceptual model for the prediction of energy transmission in presence of emergent permeable low crested structures. The transmitted wave is reconstructed from the superposition of perturbations generated leeward the structure by filtration and overtopped volumes. The model requires only structure geometry and incident wave conditions (wave height, period). A fair agreement is obtained by comparing the predicted transmission coefficients and wave spectra with measurements performed in wave flume and wave basin.     

Wave overtopping and piling-up at permeable low crested structures

The paper aims at providing a simple model for evaluating piling-up, overtopping, filtration and rip currents for low crested structures. The model is essentially based on mass and momentum balance and on resistance laws that relate piling-up and mass fluxes. A procedure is suggested and validated against 2D and 3D experimental data. This procedure is innovative with respect to existing formulations since it applies both to emerged and submerged structures and it simultaneously accounts for structure permeability, return flow through gaps and dissipative effects.     

Wave overtopping and induced currents at emergent low crested structures

This paper deals with wave overtopping associated to low emergent detached breakwaters. It starts presenting the various mechanisms which define the functional behaviour of detached breakwaters which are frequently overtopped. The emphasis is on the role played by overtopping and how this contributes to the wave pumping in the area around the structure. The paper then reviews the available formulations for predicting overtopping, considering the sensitivity of various equations to climatic drivers and their suitability for low crested coastal structures. The paper then analyzes nearshore circulation models and how overtopping discharges can be included. This is illustrated with a sample Q-3D model by analyzing the differences obtained with/without overtopping. The emphasis is on the implications for the functional design of the structure and its morpho-hydrodynamic impact. The main conclusion is the sensitivity of the functional design of such structures to the underlying hydrodynamics processes and the importance to explicitly include overtopping for numerical simulations of the morpho-hydrodynamic behaviour of low crested breakwaters.     

Hydrodynamic and morphodynamic response of isolated and multiple low crested structures: Experiments and simulations

Low crested structures for beach defence purposes are frequently configured in the form of cells. This paper investigates the hydrodynamic and morphological response of such defence schemes by means of laboratory experiments and numerical simulations.Experiments were carried out at the large mobile-bed basin of the “Laboratorio di Idraulica Costiera” of the “Politecnico di Bari”, IT. Tests peculiarity is the simultaneous simulation of three different types of lateral confinement: a channel, representative of an indefinitely long structure, and two areas with narrow and wide gaps, representative of a common scheme and of an almost isolated structure respectively. Submerged, zero freeboard and emerged conditions were tested. A typical storm of the Northern Adriatic sea was reproduced by 6 wave attacks.Water level and currents were measured in front and behind the structures, at gaps and roundheads. Results, focusing on rip current intensities and piling-up, are presented and discussed. An extensive plan view of wave intensities and flow patterns inside the basin is provided through numerical simulations with MIKE 21 numerical suite.The sand bed was surveyed along 30 profiles covering the narrow gap area and the isolated structure roundheads. For the submerged conditions tests, 15 of these profiles and the shoreline position were monitored after each step of the simulated storm.Average and maximum values of local erosion at the structure toe are presented. Time evolution of erosion at gaps is related to the main hydrodynamic variables through Bijker sediment transport formula. Evaluation of volume changes in the protected area shows that sand is in average trapped behind the barriers, being transported offshore from gaps and returning inshore over the crest. The observed and reconstructed transport mechanism is a combination of bed load and suspended transport, the latter being slightly more important.Bed level changes are well predicted by morphodynamic simulations performed with MIKE 21 CAMS.     

Structural stability of detached low crested breakwaters

The aim of the paper is to describe hydraulic stability of rock-armoured low-crested structures on the basis of new experimental tests and prototype observations.Rock armour stability results from earlier model tests under non-depth-limited long-crested head-on waves are reviewed.Results from new 2-D and 3-D model tests, carried out at Aalborg University, are presented. The tests were performed on detached low-crested breakwaters exposed to short-crested head-on and oblique waves, including depth-limited conditions. A formula that corresponds to initiation of hydraulic damage and allows determining armour stone size in shallow water conditions is given together with a rule of thumb for the required stone size in depth-limited design waves.Rock toe stability is discussed on the basis of prototype experience, hard bottom 2-D tests in depth-limited waves and an existing hydraulic stability formula. Toe damage predicted by the formula is in agreement with experimental results. In field sites, damage at the toe induced by scour or by sinking is observed and the volume of the berm is often insufficient to avoid regressive erosion of the armour layer.Stone sinking and settlement in selected sites, for which detailed information is available, are presented and discussed.     

Unfinished business: Taiwan's experience with rights-based coastal fisheries management

This paper examines a case involving a mix of Territorial Use Rights in Fisheries, co-management and the competition for using coastal zones. In the 2000s, Taiwan's government initiated a remodeling of the fishery right system, which is a rights-based approach to fisheries management, as an attempt to address conflicts between fishers and developers regarding the use of coastal space and to put community-based co-management into practice. The paper particularly compares the system before and after 2000 and identifies areas of concern in the implementation of the remodeled system. The results show that the government's support for this system signifies progress in the right direction. However, concerns emerge, mostly involving fishers' low participation, fishermen's association's lack of technical skills and financial resources, and the division of management responsibility. The government is advised to play a more active role in dealing with these concerns. Finally, the paper reveals that the factor of competition for using coastal zones poses a challenge to co-management, and suggests a holistic view with integrated coastal management or marine spatial planning practices, for developing co-management under the fishery right system.     

The role of the European Community in the Mediterranean coastal zone management

The objective of this paper is to focus on the role of the European Community (EC) in the management of the coastal zones of the Mediterranean. The EC performs this role at two levels of involvement: with respect to its Mediterranean member states and through the Euro-Mediterranean co-operation, in co-ordination with international and regional initiatives, such as those of the United Nations (Mediterranean Action Plan (MAP)) and the World Bank. According to this, the coastal policy of the EC is considered with special attention to past and current developments, and the main policy objectives and instruments are discussed. This review is followed by a brief analysis of the EC Mediterranean coastal zone: the general use and development patterns, the main pressures bearing upon it, and its definition from a legal and administrative perspective. An evaluation of the role of the EC in the Mediterranean context then follows, with particular reference to the ongoing developments of the Euro-Mediterranean co-operation within MAP and the Barcelona Convention system. On this basis, conclusions are drawn on the need to improve the EC Mediterranean coastal policy through a strengthened integration between the various EC sectoral policies, and between these policies and the policies of the member states, and through an optimised co-ordination with MAP.     

The new wave overtopping database for coastal structures

Significant effort has been made to generate a homogeneous database on wave overtopping consisting of more than 10,000 irregular wave overtopping tests from more than 160 independent projects or test series, each described by means of 31 parameters. Many coastal structures, including dikes, rubble mound breakwaters, berm breakwaters, caisson structures and combinations have been considered and have been schematised for inclusion in the database. All these overtopping tests are represented by over 300,000 numbers in the database.     

Rethinking post-tsunami integrated coastal management for Asia-Pacific

The December 2004 Indian Ocean tsunami wrought environmental damage beyond the normal framework of integrated coastal management and has implications for coastal management in Asia-Pacific in the post-tsunami phase. Fieldwork conducted on the coasts of four tsunami-affected countries in 2005 and 2006 identified several “practitioner-type” issues that would have implications for ICM policy. These include the loss of land with accompanying land tenure problems; the safety zone in conflict with the buffer zone; the need for better integration of livelihoods restoration with the rehabilitation of coastal ecosystems; and the inclusion of tsunami mitigation in the larger framework of climate change mitigation. A discussion of these issues and future role of ICM would provide a fresh perspective to policy-practice of ICM. A proposal is made to study various development pathways of selected coastal villages as they recovered in the post-tsunami phase.     

Modeling of storm-induced coastal flooding for emergency management

This paper describes a model package that simulates coastal flooding resulting from storm surge and waves generated by tropical cyclones. The package consists of four component models implemented at three levels of nested geographic regions, namely, ocean, coastal, and nearshore. The operation is automated through a preprocessor that prepares the computational grids and input atmospheric conditions and manages the data transfer between components. The third generation spectral wave model WAM and a nonlinear long-wave model calculate respectively the wave conditions and storm surge over the ocean region. The simulation results define the water levels and boundary conditions for the model SWAN to transform the storm waves in coastal regions. The storm surge and local tides define the water level in each nearshore region, where a Boussinesq model uses the wave spectra output from SWAN to simulate the surf-zone processes and runup along the coastline. The package is applied to hindcast the coastal flooding caused by Hurricanes Iwa and Iniki, which hit the Hawaiian Island of Kauai in 1982 and 1992, respectively. The model results indicate good agreement with the storm-water levels and overwash debris lines recorded during and after the events, demonstrating the capability of the model package as a forecast tool for emergency management.     

Wave run-up on bermed coastal structures

Reliable estimation of wave run-up is required for the effective and efficient design of coastal structures when flooding or wave overtopping volumes are an important consideration in the design process. In this study, a unified formula for the wave run-up on bermed structures has been developed using collected and existing data. As data on berm breakwaters was highly limited, physical model tests were conducted and the run-up was measured. Conventional governing parameters and influencing factors were then used to predict the dimensionless run-up level with 2% exceedance probability. The developed formula includes the effect of water depth which is required in understanding the influence of sea level rise and consequent changes of wave height to water depth ratio on the future hydraulic performance of the structures. The accuracy measures such as RMSE and Bias indicated that the developed formula is more accurate than the existing formulas. Additionally, the new formula was validated using field measurements and its superiority was observed when compared to the existing prediction formulas. Finally, the new design formula incorporating the partial safety factor was introduced as a design tool for engineers.     

Integrated coastal fisheries management

There are two principal threats to sustainable coastal fisheries. The concern which has been evident in most parts of the world for many years is the existence of open access to fisheries which has led to over-capitalization, over-fishing of the resource and, often, conflict. Increasingly in recent years, however, a second threat has become apparent. This is the loss of fish habitat and deterioration of water quality brought about by environmental changes generated in other sectors. Integrated coastal fisheries management addresses these issues through a strategy in which the removal of open access plays the key role, supported by elements such as creation of awareness, local participation in management, training and research, and improved sectoral coordination and planning. It is noted that, very often, the amelioration of the second of the two principal threats may be dependent on the fishery sector resolving the first.     

THESEUS decision support system for coastal risk management

While planning coastal risk management strategies, coastal managers need to assess risk across a range of spatial and temporal scales. GIS-based tools are one efficient way to support them in the decision making process through a scenarios analysis starting from social, economic and environmental information integrated into a common platform. However, this integration process requires a significant effort from a team of scientists in terms of a) identifying the appropriate scales and data resolution for analysing social, environmental and economic issues; b) selecting and linking an appropriate set of tools to build a coupled model; c) representing key emerging (and hence challenging) research issues, such as risk perception and social resilience in the model; d) developing multi-criteria analysis to integrate social, environmental, economic impacts; and e) accounting for the expectations of the stakeholders and therefore optimizing the opportunity for them to interact with the tool development and with the final tool itself.In this spirit, this paper presents an open-source Spatial Decision Support System developed within the THESEUS Project to help decision makers to scopeg optimal strategies to minimise coastal risks. The exploratory tool allows the users to perform an integrated coastal risk assessment, to analyse the effects of different combinations of engineering, social, economic and ecologically based mitigation options, across short (2020s), medium (2050s) and long-term (2080s) scenarios, taking into account physical and non-physical drivers, such as climate change, subsidence, population and economic growth.     

Implications for place attachment in coastal Reserve management

This study determined the characteristics of North Carolina Coastal Reserve and North Carolina National Estuarine Research Reserve (jointly referred to as Reserve) visitors, visitor opinions of site conditions, visitor understanding of site management objectives, and patterns of visitation. The latter were investigated to obtain a proxy of place attachment and its effects on knowledge of ownership and perceptions of management. Data were collected on demographics, use patterns, visitor perceptions, and visitor knowledge during the period of 25 May-28 October, 2007. Visitors were educated, wealthy, older, racially homogeneous, and frequent returnees. The majority of respondents supported existing management activities and the implementation of additional use restrictions should site conditions deteriorate. Data indicated that respondents were unaware of which agency manages the Reserve sites or its mission. These findings suggest that management needs to engage in more education of the visiting public. Sensitizing the public to the mission of the Reserve and increasing place attachment could decrease negative visitor impacts.     

Heritage management plans and integrated coastal management

This paper examines at the origins of coastal zone management and planning in England and from that, how integrated coastal zone management techniques were developed. The lack of heritage management planning in coastal plans in England is discussed and put into context of ‘integrated heritage zone management’ approaches. Having looked at these two systems, examples of good practice are discussed. The concept of spatial planning is also discussed and the opportunities that this might offer for integrating coastal and heritage planning in the Solent are considered.     

The opportunities of spatial planning for integrated coastal management

This paper explains the nature of spatial planning and its incorporation into amended town and country planning legislation for England. It comments on current coastal management in England, including discussion on marine spatial planning, and examines how the new planning legislation provides opportunities for implementing aspects of coastal policy through planning, using shoreline management and coastal regeneration as examples. It considers how these opportunities may be developed for the Solent. The paper concludes that these opportunities must be seized if the longer-term sustainable future of the English coast is to be secured.     

Integrated monitoring of the hydro-morphodynamics of a beach protected by low crested detached breakwaters

The aim of this paper is to propose an integrated low cost system for monitoring the performance of beach defence works during storms. For this purpose, the site of Igea Marina, Northern Adriatic Sea, Italy, which is protected by low crested detached breakwaters, is selected. The monitoring system is composed by a video installation, for the identification of the shoreline position and of the intertidal bathymetry at high space and time resolution, and a 2DH numerical model, to reconstruct the hydrodynamics induced by coastal defenses. The accuracy of the monitoring system is verified against available measurements of waves and currents performed during a field campaign with acoustic Doppler profilers. Assimilation of data on the shoreline position in 2DH model operatively working is challenging in the improvement of the production of risk maps. These show the current intensities and flooded areas during forecasted storms. First promising results suggest the possibility of setting up an early warning tool.     

Numerical investigations of wave overtopping at coastal structures

Under the numerical modelling work package of the EU funded CLASH project, the time accurate, free surface capturing, incompressible Navier–Stokes solver AMAZON-SC has been applied to study impulsive wave overtopping at Samphire Hoe, near Dover in the United Kingdom. The simulations show that the overtopping process on this vertical, sheet pile, seawall is dominated by impulsive, aerated, near vertical overtopping jets. In order to perform the simulations AMAZON-SC has been extended to incorporate an isotropic porosity model and for validation purposes the solver has been applied to study overtopping of a low crested sea dike and a 10:1 battered wall. The results obtained for the battered wall and Samphire Hoe tests are in good agreement both with predicted overtopping discharges calculated using the UK overtopping manual and with available experimental results.