M. Kok

Pairwise-comparison methods in multiple objective programming, with applications in a long-term energy-planning model

Abstract We propose to use pairwise comparisons within the framework of ideal-point or reference-point methods for multi-objective programming. The decision makers are requested to estimate the ratios which are acceptable for deviations from the ideal vector. Thereafter, we seek the nearest feasible solution using the Tchebycheff norm. In this paper we sketch the pairwise-comparison methods, some aspects of magnitude scaling, and the ideal-point methods. We show the results of our numerical experiments in long-term energy planning with nine objective functions. Finally, we present a preliminary evaluation of the combined method on the basis of its possible contribution to interactive decision analysis.

Flood Risk Assessment in the Netherlands: A Case Study for Dike Ring South Holland

Large parts of The Netherlands are below sea level. Therefore, it is important to have insight into the possible consequences and risks of flooding. In this article, an analysis of the risks due to flooding of the dike ring area South Holland in The Netherlands is presented. For different flood scenarios the potential number of fatalities is estimated. Results indicate that a flood event in this area can expose large and densely populated areas and result in hundreds to thousands of fatalities. Evacuation of South Holland before a coastal flood will be difficult due to the large amount of time required for evacuation and the limited time available. By combination with available information regarding the probability of occurrence of different flood scenarios, the flood risks have been quantified. The probability of death for a person in South Holland due to flooding, the so-called individual risk, is small. The probability of a flood disaster with many fatalities, the so-called societal risk, is relatively large in comparison with the societal risks in other sectors in The Netherlands, such as the chemical sector and aviation. The societal risk of flooding appears to be unacceptable according to some of the existing risk limits that have been proposed in literature. These results indicate the necessity of a further societal discussion on the acceptable level of flood risk in The Netherlands and the need for additional risk reducing measures.

A Bayesian failure model based on isotropic deterioration

Abstract In this paper, we focus on determining a new failure model for hydraulic structures. The failure model is based on the only information which is commonly available: the amount of deterioration averaged over a finite or an infinite time-horizon. By introducing a prior density for the average deterioration per unit time, we account for uncertainty in a decision problem. Advantages of our Bayesian approach are that we base our probabilistic models on a physical observable quantity, the deterioration, and that the probabilities of preventive repair and failure can be expressed explicitly conditional on the average deterioration. One illustration from the field of hydraulic engineering is studied.

The interface with decision makers and some experimental results in interactive multiple objective programming methods

Abstract We discuss the basic concepts of interactive methods in multiple objective linear programming. The underlying mathematical formulation is investigated. It turns out that these methods are all based on three different types of scalarization. This explains the exchange of information—the interface—between the decision makers and the model. Problems in designing this interface will be investigated using results from psychology concerning the ability of a human being to oversee a large number of stimuli. We present the results of some practical experiments with a model of the energy system in the Netherlands, and finally we draw some conclusions concerning the possible use of interactive methods in long-term planning.

Optimal Maintenance Decisions for the Sea-Bed Protection of the Eastern-Scheldt Barrier

To prevent The Netherlands from flooding, a flood defence system has been constructed, which must be inspected and, when needed, repaired. Therefore, one might be interested in obtaining cost-optimal rates of inspection, i.e. rates of inspection for which the expected maintenance costs are minimal and for which the flood defence system is safe.

OPTIMAL MAINTENANCE DECISIONS FOR DIKES

To protect the Dutch polders against flooding, more than 2500 km of dikes have been constructed. Due to settlement, subsoil consolidation, and relative sea-level rise, these dikes slowly sink “away into the sea” and should therefore be heightened regularly (at present, every 50 years). In this respect, one is interested in safe and cost-optimal dike heightenings for which the sum of the initial cost of investment and the future (discounted) cost of maintenance is minimal.For optimization purposes, a maintenance model has been developed for dikes subject to uncertain crest-level decline. On the basis of engineering knowledge, crest-level decline has been modeled as a monotone stochastic process with expected decline being either linear or nonlinear (i.e., linear after transformation) in time. For both models and for a particular unit time, the increments are distributed according to mixtures of exponentials.In a case study, the maintenance decision model has been applied to the problem of heightening the Dutch “Oostmolendijk.”

EvacuAid: A Probabilistic Model to Determine the Expected Loss of Life for Different Mass Evacuation Strategies During Flood Threats

Evacuation of people in case of a threat is a possible risk management strategy. Evacuation has the potential to save lives, but it can be costly with respect to time, money, and credibility. The consequences of an evacuation strategy depend on a combination of the time available, citizen response, authority response, and capacity of the infrastructure. The literature that discusses evacuations in case of flood risk management focuses, in most cases, only on a best-case strategy as a preventive evacuation and excludes other possible strategies. This article introduces a probabilistic method, EvacuAid, to determine the benefits of different types of evacuation with regards to loss of life. The method is applied for a case study in the Netherlands for preventive and vertical evacuation due to flood risk. The results illustrate the impact of uncertainties in available time and actual conditions (e.g., the responses of citizens and authorities and the use of infrastructure). It is concluded that preparation for evacuation requires adaptive planning that takes preventive and vertical evacuation into account, based on a risk management approach.

Ten building blocks for sustainable water governance: an integrated method to assess the governance of water

A three-step interdisciplinary method to assess approaches to water shortage, water quality and flood risks is presented. This method, based on water system analysis, economics, law and public administration, seeks to create common understanding based on newly developed concepts and definitions. First, generating content knowledge about the water system and about values, principles and policy discourses. Second, providing an organizational process with sufficient stakeholder involvement, insight into the trade-off between social objectives, and attribution of responsibilities in addition to regulations and agreements. Finally, implementing the agreed service level through adequate infrastructure, enforcement and conflict resolution.

On the convergence of reference point methods in multiobjective programming

Abstract The purpose of this paper is to present some results about the convergence of interactive reference point methods in multiobjective programming. In particular, we describe how dual information may guide the decision maker in his choice of the successive reference points. In the literature different convergence models have been proposed. The analyst may induce convergence by selecting appropriate rules of the communication. Or he may rely on the learning process of the decision maker to induce some kind of ‘psychological’ convergence. In neither case are the activities of the decision maker precisely described. Consequently, the quality of the final decision cannot be established, and the question of convergence remains an unsolved issue. We describe different ways in which the decision maker may select his successive reference points, and we discuss the convergence of the resulting reference point procedures. Also, we comment on the relevance of these different assumptions about the decision makers behavior. The procedures are illustrated by a small numerical example.

Coastal Defense and Societal Activities in the Coastal Zone: Compatible or Conflicting Interests?

Abstract World-wide coastal zones are subject to physical and societal changes. Due to climate change sea level is expected to rise and storm conditions may become more intensive. Both may lead to shore erosion intensification in the coastal zone. Moreover, the coastal zone is intensely used for societal development. The pressure upon the coast increases. It may be questioned whether coastal defence is compatible with spatial development in the coastal zone. To guide the consequences of climate change and the societal developments in a responsible manner, spatial decisions have to be taken cautiously. A long-term coastal vision is important to ensure safety in the future and to gain as much profits from the economic opportunities offered by the coastal zone as possible. This problem is resolved here by an economic optimisation method. Long-term coastal policies are economically assessed with a stochastic economic optimisation model. This model combines the hydraulic and morphological processes in the coastal system with the maintenance measures and the socioeconomic and ecological activities. The maintenance costs in relation to the possible damage resulting from coastal recession are optimised with the model. The model is influenced by various uncertainties, which affect the optimisation results. Therefore, uncertainty distributions have been assessed and Monte Carlo simulations are made with the model. The model is applied to the Dutch coast. The expected minimal total costs of various coastal policies are estimated. Optimisation results show that coastal defence and societal activities in the coastal zone in the Netherlands are indeed compatible.