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Engineering solutions are widely used for the mitigation of flood and erosion risks and have nowadays to face new challenges due to the expected effects induced by climate change in particular sea level rise and increase of storminess. This Chapter describes both active methods of mitigation based on the reduction of the incident wave energy, such as the use of wave energy converters, floating breakwaters and artificial reefs, and passive methods, consisting of increase in overtopping resistance of dikes, improvement of resilience of breakwaters against failures, and the use of beach nourishment as well as tailored dredging operations.

CLASH is concentrating on investigations of wave overtopping for different structures in prototype and in laboraty. The model investigations have focussed on wave overtopping and the comparison of overtopping results from small-scale model tests and prototype measurements. Possible differences in the results from small-scale tests and prototype were analysed with respect to measurement accuracy as well as model and scale effects. This report proposes a methodology to assess the aforementioned effects and to provide the uncertainties and correction factors for quantifying the various influences when performing model tests.

The present guidelines are specifically dedicated to Low Crested Structures on attempt to provide methodological tools both for the engineering design of structures and for prediction of performance and environmental impacts of such structures. It is anticipated that the guidelines will provide valuable inputs to coastal zone management plans. The target audience for this set of guidelines is consulting engineers or engineering officers and officials of local authorities dealing with coastal protection schemes. The guidelines are also of relevance in providing a briefing of current best practice for local and national planning authorities, statutory agencies and other stakeholders in the coastal zone. The guidelines have been drafted in a generic way to be appropriate throughout the European Union taking into regard current European Commission policy and directives to promote sustainable development and integrated coastal zone management.

Guidance on selection of breakwater types and related design safety levels for breakwaters are almost non-existent.

In this paper is presented an improved version of the overtopping formula by Lykke Andersen & Burcharth (2004)valid for berm breakwaters with initial slopes of 1:1.25. In the present paper guidelines is given on how to modify the formula to take into account the initial slope angle. Further the formula is improved so it gives reliable estimates also for more stable structures. The extension of the overtopping formula is based on analysis of front slope stability data from many different data sets. In most cases there is only a small difference between the Lykke Andersen & Burcharth (2004) formula and the present improved formula. However, for a more stable structure and low wave steepness the improved formula performs better. Six different data sets are used to study the validity of the Lykke Andersen & Burcharth (2004) formula, the present improved formula and the CLASH neural network model. The present improved formula seems to be the best choice. The CLASH NN-Model performs very well for berm breakwater data sets included in the fitting of the NN-Model, but much worse for those not included. This demonstrates some degree of overlearning of the neural network due to limited data for berm breakwaters.

The investigation concerns the design of a new internal breakwater in the main port of Ibiza. The objective of the model tests was in the first hand to optimize the cross section to make the wave reflection low enough to ensure that unacceptable wave agitation will not occur in the port. Secondly wave overtopping was studied as well.

Optimum design safety levels for rock and cube armoured rubble mound breakwaters without superstructure are investigated by numerical simulations on the basis of minimization of the total costs over the service life of the structure, taking into account typical uncertainties related to wave statistics and structure response. The study comprises the influence of interest rate, service lifetime, downtime costs and damage accumulation. Design limit states and safety classes for breakwaters are discussed. The results indicate that optimum safety levels are somewhat higher than the safety levels inherent in conventional deterministic designs. Moreover, the analyses show that conservative designs involving very little repair over service lifetime are only marginally more expensive that cost optimised designs. Optimum design safety levels for rock and cube armoured rubble mound breakwaters without superstructure are investigated by numerical simulations on the basis of minimization of the total costs over the service life of the structure, taking into account typical uncertainties related to wave statistics and structure response. The study comprises the influence of interest rate, service lifetime, downtime costs and damage accumulation. Design limit states and safety classes for breakwaters are discussed. The results indicate that optimum safety levels are somewhat higher than the safety levels inherent in conventional deterministic designs. Moreover, the analyses show that conservative designs involving very little repair over service lifetime are only marginally more expensive that cost optimised designs.

Natural rock with high density is widely used in the Scandinavian countries. However, the use of natural rock with density higher than 2:9t=m3 is ordinarily associated with some kind of problem solving, e.g. where normal density stones have to be replaced with heavier stones without increasing the construction volume or layer thickness. Most common design formulae do not give a clear conclusion on the in°uence of the rock density on the stability. The present paper presents results of small and large scale model tests in which is used rock with different densities. It is shown that the positive effect on stability from the increased density is overestimated by conventional armour stability formulae in case of steep slopes. The infuence of the density depends on the slope angle and the type of armour units.

This report presents the conclusions of Panel 1: Construction engineering, Production and Operation. The Research Council of Norway (NFR) appointed three expert panels to evaluate Research in Engineering Science in Norway . This report presents the conclusions of Panel 1: Construction engineering, Production and Operation. The Research Council of Norway (NFR) appointed three expert panels to evaluate Research in Engineering Science in Norway .

Overtopping and rear slope stability of reshaping and non-reshaping berm breakwaters have been studied in a wave flume. A total of 695 tests have been performed to cover the influence of crest freeboard, crest width, berm width, berm elevation, stone size and sea state. Formula for average overtopping discharge that includes these parameters has been derived. The measurements show good correlation between average overtopping discharge and rear slope damage.

This report deals with the laboratory tests performed to give additional information on overtopping of reshaping breakwaters performed at Aalborg University, 2003-2004.

The objective of the report is to identify the minimum cost safety levels for standard types of breakwaters in small/moderate and deeper water. The objective of the report is to identify the minimum cost safety levels for standard types of breakwaters in small/moderate and deeper water.

The report contains the results of main armour stability, toe stability and overtopping tests for the rehabilitation of the Genova Voltri rubble mound breakwater. The report contains the results of main armour stability, toe stability and overtopping tests for the rehabilitation of the Genova Voltri rubble mound breakwater.

The report is focussing on wave overtopping for different structures and in laboratory. The main scientific objectives of CLASH are to solve the problem of possible scale effects for wave overtopping and to produce a generic prediction method for crest height design or overtopping assessment. This report deals with the laboratory tests performed to give additional information on overtopping of reshaping breakwaters performed at Aalborg University, 2003-2004.

Identification of optimum reliability levels for coastal structures is considered. A class of breakwaters is considered where no human injuries can be expected in cases of failure. The optimum reliability level is identified by minimizing the total costs over the service life of the structure, including building costs, maintenance and repair costs, downtime costs and decommission costs. Different formulations are considered. Stochastic models are presented for the main failure modes for rubble mound breakwaters without superstructures, typically used for outer protection of basins. The influence on the minimumcost reliability levels is investigated for different values of the real rate of interest, the service lifetime, the downtime costs due to malfunction and the decommission costs.

This report deals with the laboratory tests performed to give additional information on obliqueness, short-crested waves and directional spreading performed at Aalborg University, 2004. 736 tests have been performed to give more information on the influence of wave direction and directional spreading on wave overtopping. This report deals with the laboratory tests performed to give additional information on obliqueness, short-crested waves and directional spreading performed at Aalborg University, 2004. 736 tests have been performed to give more information on the influence of wave direction and directional spreading on wave overtopping.

The Port of La Coruna, Spain is to be expanded by a new port at Punta Langosteria. The Port Authority of La Coruna has by contract of October 28, 2002, retained the Hydraulic and Coastal Engineering Laboratory at Aalborg University, Denmark, to make a systematic model test study of the breakwater roundhead situated in 40 meter water depth.

A consequence of Froude-scaling of wave dominated hydraulic models is disproportion of viscosity and surface tension. The flow domain related to the action of incoming waves on a sloping porous structure changes in space and time. During the run-up phase the flow domain can be separated in a jet like surface flow domain and a porous flow domain.

The paper presents an overview of the design guidelines for low crested structures (LCS's) to be applied in coastal protection schemes. The design guidelines are formulated as a part of the research project: Environmental Design of Low Crested Coastal Defence Structures (DELOS) within the EC 5FP 1998-2002. The Guidelines comprise engineering aspects related to morphological impact and structure stability, biological aspects related to ecological impact, and socio-economical aspects related to the implementation of LCS-schemes. The guidelines are limited to submerged and regularly overtopped emergent structures. The paper presents an overview of the design guidelines for low crested structures (LCS's) to be applied in coastal protection schemes. The design guidelines are formulated as a part of the research project: Environmental Design of Low Crested Coastal Defence Structures (DELOS) within the EC 5FP 1998-2002. The Guidelines comprise engineering aspects related to morphological impact and structure stability, biological aspects related to ecological impact, and socio-economical aspects related to the implementation of LCS-schemes. The guidelines are limited to submerged and regularly overtopped emergent structures.

Coastal structures are used in coastal defence schemes with the objective of preventing shoreline erosion and flooding of the hinterland. Other objectives include sheltering of harbour basins and harbour entrances against waves, stabilization of navigation channels at inlets, and protection of water intakes and outfalls.

Planning and design procedures for coastal projects are described.

Conventional design practice for coastal structures is deterministic in nature and is based on the concept of a design load which should not exceed the resistance (carrying capacity) of the structure. The design load is usually defined on a probabilistic basis as a characteristic value of the load, for example the expectation (mean) value of the 100-year return period event. However, this selection is often made without consideration of the involved uncertainties. In most cases the resistance is defined in terms of the load that causes a certain design impact or damage to the structure, and it is not given as an ultimate force or deformation. This is because most of the available design formulae only give the relationship between wave characteristics and some structural response, such as runup, overtopping, armor layer damage, etc. An example is the Hudson formula for armor layer stability.

Forsøg med anvendelse af lodrette drænrør som kyststabiliseringsmetode blev igangsat ved Gl. Skagen i januar 1999.

The paper deals with concepts of safety implementation in design. An overall safety factor concept is evaluated on the basis of a reliability analysis of a model tested rubble mound breakwater with monolithic super structure. Also discussed are design load identification and failure mode limit state equations including slip failure analysis. The paper deals with concepts of safety implementation in design. An overall safety factor concept is evaluated on the basis of a reliability analysis of a model tested rubble mound breakwater with monolithic super structure. Also discussed are design load identification and failure mode limit state equations including slip failure analysis.

Forsøg med anvendelse af lodrette drænrør som kyststabiliseringsmetode blev igangsat ved Gl. Skagen i januar 1999.

Codes of practice for building and civil engineering works have been produced since 1893 by the "Danish Society of Engineers". Among the early codes are: Reinforces concrete structures (1908, 1943), calculation of reinforced concrete structures in harbour works (1926), Harbour Works (1927), Steel structures (1941). The codes were based on the principle of allowable stresses. However, already in 1948 a Danish consulting engineer used a partial safety factor concept for a power station design in order to secure satisfactory safety. The concept was in fact old as it was used by Gerber in his design of a railway bridge over river Mainz. Codes of practice for building and civil engineering works have been produced since 1893 by the "Danish Society of Engineers". Among the early codes are: Reinforces concrete structures (1908, 1943), calculation of reinforced concrete structures in harbour works (1926), Harbour Works (1927), Steel structures (1941). The codes were based on the principle of allowable stresses. However, already in 1948 a Danish consulting engineer used a partial safety factor concept for a power station design in order to secure satisfactory safety. The concept was in fact old as it was used by Gerber in his design of a railway bridge over river Mainz.

A consistent risk-based design philosophy for vertical breakwaters is proposed. The design philosophy consists of a two-step approach. The first step is the definition of the main function of the breakwater, which leads to a definition of failure. The second step is the choice of the acceptable safety level. This may be done on the basis of comparison to existing codes, or by applying economic optimisation. Both methods are introduced in the paper. A consistent risk-based design philosophy for vertical breakwaters is proposed. The design philosophy consists of a two-step approach. The first step is the definition of the main function of the breakwater, which leads to a definition of failure. The second step is the choice of the acceptable safety level. This may be done on the basis of comparison to existing codes, or by applying economic optimisation. Both methods are introduced in the paper

Design and construction of coastal structures have always been a challenge as engineers are working in still more exposed locations, and the former acceptance of some failures caused by the inpredictable sea is no more valid . Today it is generally expected that the coastal engineer can cope with the vagaries of nature and produce structures which will survive and function for several generations. The design tools available to us are better than ever and we can, in a rational way, deal with the uncertainties inherent in sea states and structural responses. Provided no failure mode is overlooked we can in fact design on the basis of target probability of specific damage within structure lifetime, identified by economic optimization. Design and construction of coastal structures have always been a challenge as engineers are working in still more exposed locations, and the former acceptance of some failures caused by the inpredictable sea is no more valid . Today it is generally expected that the coastal engineer can cope with the vagaries of nature and produce structures which will survive and function for several generations. The design tools available to us are better than ever and we can, in a rational way, deal with the uncertainties inherent in sea states and structural responses. Provided no failure mode is overlooked we can in fact design on the basis of target probability of specific damage within structure lifetime, identified by economic optimization.

The paper presents a summary of the recommendations for implementation of safety in breakwater designs given by the PIANC PTC IT Working Group No 12 on Analysis of Rubble Mound Breakwaters with Vertical and Inclined Concrete Walls. The working groups developed for the most important failure modes a system of partial safety factors which facilitate design to any target safety level. The paper presents a summary of the recommendations for implementation of safety in breakwater designs given by the PIANC PTC IT Working Group No 12 on Analysis of Rubble Mound Breakwaters with Vertical and Inclined Concrete Walls. The working groups developed for the most important failure modes a system of partial safety factors which facilitate design to any target safety level.

Throughout several years Gabbro rocks have been used for various coast protective constructions and breakwaters at the North Sea Coast and in inner Danish waters. So far the use of Gabbro has been based solely on calculations from Shore Protection Manuals, i.e without model tests. Compared to ordinarygranite breakwaters the smaller Gabbro constructions have proved to be very competitive. The Gabbro constructions are more stable and the smaller units makes it possible to use smaller equipment. The choice of rocks is normally based on the consultant's calculations compared to the most favorable offer. In order to exploit the advantages of Gabbro, Franzefoss Bruk, Norway; Havnecon Consulting Aps and the Aalborg University, Denmark have entered a co-operation on the development of a Gabbro rubble mound breakwater.This paper describes the development of the project and explains the savings obtained by using Gabbro instead of ordinary granite. Throughout several years Gabbro rocks have been used for various coast protective constructions and breakwaters at the North Sea Coast and in inner Danish waters. So far the use of Gabbro has been based solely on calculations from Shore Protection Manuals, i.e without model tests. Compared to ordinarygranite breakwaters the smaller Gabbro constructions have proved to be very competitive. The Gabbro constructions are more stable and the smaller units makes it possible to use smaller equipment. The choice of rocks is normally based on the consultant's calculations compared to the most favorable offer. In order to exploit the advantages of Gabbro, Franzefoss Bruk, Norway; Havnecon Consulting Aps and the Aalborg University, Denmark have entered a co-operation on the development of a Gabbro rubble mound breakwater.This paper describes the development of the project and explains the savings obtained by using Gabbro instead of ordinary granite.

An empirical model for time variation of overtopping discharge is verified through a comparison to experimental data. The verification is performed for a parameter range covering overtopping ramps typically used in wave energy converters utilizing overtopping.