Project in the spotlight: ‘Security Risks of Flood Defences’

This study is the result of an LDE funded research project, conducted by the team members listed below. The main goals targeted in the study were to model the destructive power of physical modus operandi and to determine gaps in flood security. Initially, the scope of the study was set rather generic. The study started as a comparative study of flood barriers in the Netherlands (and in some cases abroad). Based on the results of individual flood barrier observations, a second analysis was then made in order to categorize types of barriers and to find out whether each type of barrier can be coupled to security risk data typical for that type of barrier.  

An operational security oriented research approach was adopted by Jos de Lange. He studied the vulnerability of flood defences based on a military operational analysis and security practice. Since there is little scientific data available regarding physical threat to flood defences, the results of this study depend for a large part on historical research and qualitative analysis (of the structure) of existing flood barriers. The study has produced a matrix combining (vulnerabilities of) flood barrier constructions and the implied security risks. For a security professional, such a matrix gives clear indications which security measures should be implemented, and in case of limited resources, in what order. In case of security threats, a normal order of defence layer implementation would be to establish defence perimeters, limit access to the most vulnerable parts of the object to be protected and organize supervision and rapid response in case of imminent perimeter breaches.

In the (access restricted) study by Tobias Melin, a starting point was the assumption that extremist groups will have little resource to (large amounts of) explosives, and therefore have to resort to limited use of explosives in order to disrupt flood defences. The scientific element in the Melin study is then to calculate the force necessary to damage a dike body, with what results. For various reasons, Melin concludes that such an attack on dike bodies is less likely. Melin’s approach can be called that of a (military) engineer. The basic question for a military engineer is: ‘I have an obstacle in front of me, how to remove it quickly’. In many cases, this would be by using explosives. One should also keep in mind that military engineers, when there is no obstacle, tend to blow up things in order to create an obstacle to prevent the enemy from advancing. The most likely victims for such actions are bridges across rivers and canals.

Melin’s assumption that most extremist groups have only limited access to large amounts of explosives may be considered debatable. The Oklahoma City bombing, on April 19, 1995, shows that persons eager enough can easily acquire the means for large scale attacks (that is, where it concerns the results). That is why security professionals ask themselves various questions such as about motive, possible targets, possible results and the possible ‘advertising’ impact. Follow-up questions then would concern possible locations, opportunity, ways of access and escape, resulting in possible modus operandi. In a military approach these questions would then be answered by making up various scenario’s in which all possible answers to these questions could be answered (and responded to). A more scientific approach would then be to statistically analyse these scenarios by way of, for instance, a game theory approach. In this study we have used all three approaches, albeit in varying degrees and limited by resources such as time and the restriction to use only public sources.

The study has resulted in an extensive report (170 pages) and will be published as Volume 2 within the book series  Integrated Security Science by De Gruyter (


Drs. Mr. Jos de Lange (Delft University of Technology)
Tobias Melin MSc (Delft University of Technology) Bas Kolen (Delft University of Technology)
Prof.dr. Edwin Bakker (Leiden University)
Pieter Kuhlmann MSc (Leiden University) Pieter van Gelder (Delft University of Technology)