Geographical Societal Risk: A Useful Method for Understanding Societal Risk

Dutch legislation on safety and land use planning: Being a densely populated country, the Netherlands has extensive experience using safety regulations in land-use planning. Risk criteria have to be verified in urban development planning. Individual (Locational) Risk (IR) is easy to illustrate using Iso-Risk Contours, but the concept of Societal Risk (SR) is difficult to comprehend by local authorities and land use planners. The Dutch authorities therefore identified the need for a geographic presentation of the societal risk, which would illustrate most affected (or problem) areas.

Geographical Societal Risk map: TNO has taken the opportunity to develop an area-specific approach to Societal Risks. This method considers the risks not from the perspective of the source causing the risks, but from the perspective of receivers of the risk, making it possible to quantify aggregate risk from various sources. The societal risk maps proposed by TNO uses two kinds of maps: the Societal Risk “area” map and a “contribution” map which illustrates high-risk hot spots.

Usability of maps: The method has now been implemented in a software tool and supplied to regional environmental service offices. The tool makes it possible to quickly validate the influence of a change in population distribution, for instance as a result of urban development plans. Since risk from transport activities are also incorporated, it is also possible to vary transport intensities, or changes in transport routes. The geographical feedback, provided by the maps, appeared to be very useful in the communication between risk evaluation experts, and for instance spatial planners. Furthermore, the illustrative coloured areas proved to make users much more aware of the importance and possible range of effects of potential accidents. The methodological background and application of the societal risk maps will be described in the paper.