Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

White paper on risks related to urban stormwater

The report is a "whitepaper" on risk perception, risk assessment and risk management as they are seen in the context of the DayWater project. The purpose of the white paper is to define how the DayWater project group will work with the concept of risk in relation to stormwater source control.

In chapter 2 the definition of risk, which is the basis for the whole report is introduced. To provide a common understanding for the readers the most important terminology is defined. It is discussed that the formal scientific definition of risk can be difficult to use operationally, and as a consequence the use of risk indicators is introduced in many types of risk assessment, to ease both the risk assessment and the risk communication.

The risk space is the space that is expanded by the actual risk, the perceived risk and the uncertainty of both. In chapter 3 this space is explored. A number of influencing factors and concepts are presented. It is illustrated that uncertainty, perceived risk and actual risk are strongly linked. It is emphasized that the public�s perception of risk is important when communicating about risk to a broader audience. Individuals perception of the same risk varies a lot from members of the bungee-jump society who consequently underestimate risks to members of the reflexive society who overestimate risks. It also illustrated that uncertainty can be divided into three dimensions, location, level and nature of uncertainty. Location deals with where in the urban water system the uncertainty is located, we distinguish between three subsystems; the technical system, the environmental system and the social system. At the level of uncertainty we operate with a scale from statistical uncertainty in one end over scenario uncertainty to ignorance in the other end. The nature of uncertainty is divided into reducible uncertainty and irreducible uncertainty.

Risk management in the DayWater context is explored in chapter 4. We present a frame for risk analysis that also explains how we interpret the relationship and gradual transition between hazard and vulnerability identification and/or assessment to risk characterisation. The screening tools that will be developed in Daywater will provide assistance with two different types of problems; screening of large databases of chemicals and presentation of information in GIS interfaces with the purpose of creating overview. A draft outline of the tool for screening of potential stormwater pollutants is presented. These tools will have potential applications both
within hazard and vulnerability identification and assessment.

Coping with uncertainty in risk management is of the uttermost importance. The three dimensions of uncertainty are used to construct a matrix for analysing the uncertainty of decision situations present in urban stormwater management. This matrix is beneficial when discussing and creating overview of a problem. Finally in this chapter we show that decisions can be divided into 4 different regimes based on agreement/disagreement about the goal and knowledge about the technology needed to achieve the goals. Each regime is characterised by being dominated by a certain level of uncertainty (statistical uncertainty, scenario uncertainty and ignorance), as well as by special groups of professionals and typical working methods.

That different tools are suited for different regimes, or decision situations, is important to keep in mind in the work in DayWater, which is aimed at developing an adaptive decision support system that can guide the decision maker to the right tools depending of the situation.

Chapter 5 presents the results of an inventory made on the background of 14 end user questionnaires and reports from partners. The results are presented in a matrix dividing the urban stormwater system into seven different risk objects and seven different types of risk. The inventory shows a reasonable correspondence in what combinations of object/type the endusers and the experts find the most problems. The most frequent object among the experts was the natural environment, the most mentioned type of risk was hydraulic and technical risk. The end users pointed out the natural environment and BMP�s as the objects with most risks involved. The most often mentioned types of risk were chemical and hydraulic risks.

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Resultado resumido

Reported by

Technical University of Denmark
Bygningstorvet, Building 115
DK-2800 Kg Lyngby
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