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One of the failure mechanisms of a rubble mound breakwater is the failure of its armour layer. In order to determine the stability of an armour layer, the design load has to be defined, which is in fact the wave that attacks the structure. Being a highly stochastic phenomenon, the wave action is not easily defined, while there is always some uncertainty inherent to its definition. In a deterministic calculation this uncertainty is totally overlooked, as the possible variations of the design wave height are not taken into account. In order to incorporate uncertainties into the design process, and therefore increase its reliability, probabilistic design methods should be applied. A commonly used approach is a semi-probabilistic computation on level 1, which introduces the application of partial safety coefficients, yet the indicated methods to derive and apply them do not clarify the uncertainties incorporated, adding an undefined degree of safety in the process, or end up with incorrect results under certain conditions. Another approach is a fully probabilistic computation on level 2 or 3. This type of design tackles explicitly a great deal of uncertainties, hence its results can be considered much more accurate. However it is not commonly used, due to the fact that there are not straight forward guidelines to support it, and therefore a number of critical decisions by the designers are required. The main objective of this study is to indicate the weaknesses of the existing design methods, and to suggest a design approach that is both attractive to designers and sufficiently reliable. This is achieved through application of the existing methods in an example case, whose features facilitates a critical assessment, and enables formulation of an improved approach. The chosen case is the jetties at the entrance of Galveston port, in the Gulf of Mexico, and the features of interest are the hurricane-dominated hydraulic climate and the fact that the structure is located in shallow water, meaning that the design load is determined by depth-limited waves. The design methods that are demonstrated are a classical deterministic design, a semi-probabilistic calculation on level 1 as proposed by PIANC in 1992, and a fully probabilistic calculation on level 3 with a Monte Carlo simulation. Based on the evaluation of the three design processes and the results, the new approach can be developed, which suggests a rational framework for deriving safety factors. According to it, a set of safety factors is generated which incorporate the same uncertainties as a fully probabilistic design; hence an equally reliable result is extracted. The final product is a guideline for code makers indicating the procedure to derive the safety factors and a guideline for future designers indicating the analytic steps for a proper use of the safety factors. In addition a large number of concluding remarks are summarized, which can contribute in optimizing the performed analysis. The concluding remarks refer in particular to the determination of hydraulic boundary conditions, the application of the design methods, the probabilistic model used for Monte Carlo simulation, the proposed design approach, and the safety factors derived with this approach.

This paper introduces the development of a methodology for performance of oil spill risk analysis in coastal zones through a prototype application. The main objective of the research effort is to develop the basis for a tool that can assess risks due to the occurrence of an oil spill event aiming at assisting to the risk response process. The methodology concerns the processes of probability and consequence assessment. The two processes are accomplished qualitatively with a risk prioritization based on Analytic Hierarchy Process. Being a decision-making technique, Analytic Hierarchy Process can only be used after some appropriate modifications, which transform it into a tool for prioritizing risks with respect to their probability and consequence in different oil spill scenarios. This is an approach that attempts to rationalise the risk analysis stages and to indicate the uncertainties imposed to the problem, hence creating a basis for optimization of the risk analysis results.

The tsunami that hit the north pacific coast of Japan on March 11, 2011 has been characterized as a mega disaster. It inundated over 560 square kilometers of land, devastating a large number of coastal communities, causing over 20,000 casualties and huge economic damage in Tohoku region. The purpose of this report is to give insight into the magnitude of the disaster and the response of the Japanese tsunami countermeasures to it, based on which a number of questions can be formulated regarding in which direction research should go. In the beginning some background information is given regarding the affected coastline, which is useful in order for the local disaster patterns to be understood. The core content is a description of the visited areas, the local tsunami behaviour, and the damage that took place. The report ends up with some suggestions for future research.

The Great Eastern Japan Earthquake and Tsunami of March 11, 2011 can be characterized as a catastrophe. It inundated over 560 km2 of land, devastating a large number of coastal communities, causing over 19,000 casualties and huge economic damage in the Tohoku region. Due to the relatively high frequency of tsunamis, the region was considered well prepared against extreme coastal events. Yet the event of March 11 exceeded all previous expectations and overwhelmed the Japanese disaster protection system. This book constitutes a Dutch perspective to the Japanese tsunami disaster. Its main objective is to provide a comprehensive overview of the devastating events, their impact and the implications of this catastrophe for flood risk management in Japan, in the Netherlands, and ultimately worldwide. It is in fact the outcome of an effort to derive lessons for flood risk management based on the record of a natural disaster with a magnitude that has never been recorded before. First a brief chronicle of the events of March 11 2011 is presented, followed by the consequences and actions that took place in the aftermath of the disaster. Subsequently some insight into the damage and casualties is provided through the description of field observations in September 2011. Using this information the response of the Japanese flood countermeasures to the tsunami of March 2011 is analysed from a flood risk management perspective. The book continues with an overview of the recovery efforts, and it concludes with some future challenges for developments in disaster management, including the potential of Dutch-Japanese collaborations in the field of flood risk management.

One of the failure mechanisms of a rubble mound breakwater is the failure of its armour layer. In order to determine the stability of an armour layer, the design load has to be defined, which is in fact the wave that attacks the structure. Being a highly stochastic phenomenon, the wave action is not easily defined, while there is always some uncertainty inherent to its definition. In a deterministic calculation this uncertainty is being left to engineering judgment, as the possible variations of the design wave height are not taken into account in a coherent way. In order to explicitly incorporate uncertainties into the design process, and therefore increase its reliability, probabilistic design methods should be applied. A commonly used approach is a semi-probabilistic computation, which introduces the application of partial safety coefficients. Nevertheless the indicated methods to derive and apply them do not clarify the uncertainties incorporated, adding an undefined degree of safety in the process, or end up with incorrect results under certain conditions. Another approach is a fully probabilistic computation. This type of design tackles explicitly a great deal of uncertainties, hence its results can be considered much more accurate. However it is not commonly used, due to the fact that there are not straightforward guidelines to support it, and therefore a number of critical decisions by the designers are required. This paper focuses on the application of probabilistic methods for armour layer design of rubble mound breakwaters. The main objective is to indicate the weaknesses of the previously mentioned methods, and to suggest a probabilistic design approach that is both attractive to designers and sufficiently reliable. This can be achieved through elaboration of a design example with the various methods, followed by a critical evaluation of the results.

This paper presents the development of a semi-probabilistic method for armour layer design of rubble mound breakwaters, which is based on the use of safety factors. The objective is to introduce an approach that is both attractive to designers and sufficiently reliable when a high degree of uncertainty is involved in the design process. The main focus of the analysis is the calibration and appropriate use of the safety factors, which is the key element for a reliable result.

Since 2004 there is a growing global awareness of the risks that tsunamis pose to coastal communities. Despite the fact that these events were already an intrinsic part of the culture of some countries (such as Chile and Japan), in many other places they had been virtually unheard of before 2004. Nevertheless, the frequent reoccurrence of these events in recent years has led to the emergence of a “tsunami culture” in many areas of the world, which has resulted in increased awareness, disaster preparedness and willingness of local populations to evacuate when the threat of these events arises. This paper will explore these cultural issues using as a basis questionnaires carried out by the authors during their own field visits to the last three major events (in Japan, Chile and Indonesia), and interpret these through the willingness of coastal communities to build protection measures along the shore and the impact that these can have on sustainable development.

This poster presents the framework of a decision support model for time-dependent investments in structural flood risk mitigation measures.

This paper presents an assessment of the multi-layered safety system in Tohoku, Japan based on the tsunami disaster of March 2011. The performed analysis has been based on data provided by local researchers and field observations. First an overview of the tsunami behaviour along the affected coastline of Tohoku is presented, which shows clearly that the disaster has site-specific features. The assessment that follows has a descriptive character and it is divided in two parts. First the performance of each safety layer in Tohoku is separately assessed, and conclusions are drawn for the efficiency of the system. The second part points out some implications of this disaster for the use of multi-layered safety in flood risk management.

The earthquake and tsunami of March 2011 led to death and destruction in coastal areas in Japan. A seminar was held in June 2012 for Japanese and Dutch coastal researchers to discuss lessons for the management of the risks in coastal areas associated with tsunamis, typhoons and storm surges. The seminar has highlighted important practical and theoretical issues in coastal protection, risk and emergency management, and climate change and sea level rise research that are of importance for the Netherlands and Japan and other coastal regions. The performance of the system during historical events gives important lessons for the (re)design of resilient coastal protection systems in the future. It has also been discussed how risk assessments can be utilized to determine how an effective combination of prevention, land use planning and emergency management can be implemented to minimize future risks in the coastal zone.