In the previous chapter we discussed the functioning of the bowtie model, and its significance for the development of security risk scenarios. We concluded that it can take a long time before causes and threats in the fault tree (the left side of the bowtie model) become evident in the event tree through the emergence of unwanted (immediate) effects and (later) consequences. Reason identified groups of events where wrong decisions (very) early in the fault tree may eventually lead to undesired events lining up, facilitating undesired accidents to happen at a much later time. Reason mainly looked at business processes but the same is true when it comes to terrorism, an important implicit motive in the attack vulnerability tables that we introduced in the previous chapters. In the case of (threat of) terrorist attacks the time between planning and execution can take years. The possibility of such attacks occurring depends - among others - on geopolitical circumstances and developments. Officials in charge of the protection of flood defenses told us that it is hardly feasible to calculate the likelihood of a terrorist attack. According to them, this is because there are no historical data. With this view we disagree. We think that enough data is available to say at least something about the likelihood of specific types of terrorist attack in specific circumstances. In this chapter we evaluate the probability of possible terrorist attacks against flood barriers (we use the Netherlands and Europe as an example). If we want to give a realistic estimate of the chance of such an attack occurring, we have to consider the historic context of terrorist attacks (in this case in the Netherlands). Additionally, in our quest for finding objective approaches to terrorist attack scenarios, we explore the application of game theory in scenario building in some detail.
In this closing chapter, we outline the starting points of this book, and judge if we were able to meet the goals that we set in the beginning. Then we briefly review the main conclusions that we discussed at the end of each chapter. We are not going to repeat all conclusions again. In the next and last chapter, we make some recommendations, based on the conclusions in this chapter.
If one implements security measures in or around technical installations in general, or large water works in particular, this may have safety consequences. Consider, for example, stricter access requirements that make it difficult for people to enter a building. These security measures will also make it more difficult to get out of the building. This can be a hindrance in the event of a fire. We did not include this aspect in our investigation into security risks of flood defenses. It is an intriguing question, which is worth investigating further.
In this chapter we present a summary of the main contents of this book. According to the Mayfield Handbook of Technical & Scientific Writing (Perelman, Barrett, & Paradis, 1996, 2001), an abstract is “a brief summarizing statement. . . read by parties who are trying to decide whether or not to read the main document.” However, since the main conclusions of each chapter are also included, this chapter can also be read as a summary, “which, unlike an abstract, is a document in miniature that may be read in place of the longer document” (same source). For pictures, tables, and other illustrative material, we refer to the various chapters of this book.
In this chapter we discuss the history of the Netherlands as a land of sea, rivers, levees, and polders. Water and levees are part of the Dutch genes. In order to understand the constant struggle of the Dutch against the threatening water of the sea and an abundance of rivers, we start our research in the beginning of our era. This also gives us an understanding of the development of flood defense construction techniques, and the intrinsic weaknesses of flood barrier constructions. Where it concerns basic shapes and techniques, not much has changed in flood barrier construction in the past 2,000 years.
In this chapter we continue our history of flood defenses in the Low Countries with an introduction to the Delta Plan. The Delta Plan was (and is) the major Dutch defense plan against flooding, either from the sea or from overflowing rivers. The Delta Plan has also confirmed the world renowned fame of the Dutch as the world’s leading water and flood defense engineers. The flood defenses constructed as a part of the Delta Plan show the rapid development of flood defense engineering in the past 70 years, and present a wide variety of flood defenses and flood barriers that we can use as examples to develop flood defense vulnerability tables and security threat scenarios.
In the previous chapter we discussed the design and construction of flood defenses and flood barriers in the first 21 years of the Dutch Delta Plan. We use the realization of the Delta Plan as an example for the enormous development of flood defenses and flood barriers in a relatively short time. In this chapter, we conclude our review of the Delta Plan flood barriers by looking at various storm surge barriers. As in the previous chapters, we will also assess the safety and security risks associated with these flood barriers and we extend our safety and security risk table accordingly.
In the previous chapters we went back in history to see how the construction of flood defenses developed over time. At the same time, we also looked at the safety and security aspects of those flood defenses. However, over the centuries, water has not only been a threat. It can also be a friend (if it behaves itself). In relation to security, we can learn a lot from the use of water in defensive applications. In Europe, and in Dutch history, water defenses have frequently been used as a defense against foreign invasions and dominance. Flood barriers can not only be used as defense against water, but they can also be used for retaining water. The Dutch invented an ingenious combination of waterworks for such purpose. Understanding of these constructions increases our insight into flood barrier weaknesses, and security- related vulnerabilities.