Certainty of uncertainty in evacuation for threat driven response

Evacuation is a measure taken to potentially reduce the loss of life and damage to movable goods. Evacuation is part of a portfolio of measures in a multilateral safety system that can contribute to an acceptable level of risk. Evacuation has benefits but can be costly. Therefore, the decision to call for an evacuation due to the threat of flooding results in a crisis, by definition, but can prevent a worse crisis in the case of an actual flood. This thesis focuses on effectiveness of different types of evacuation and how to address uncertainties. This thesis focuses on the Netherlands as a representative urbanized delta and investment strategies in evacuation as a part of flood risk management. Evacuation in case of the threat of flooding requires an uncomplicated approach. This is because of the complexity of preparation for low-frequency, large-scale disasters such as flooding and because of the limited risk perception by the public, decision makers and crisis managers and the number of them which are involved. It is shown that vertical evacuation or shelter in place is a better basic strategy for coping with a flood than preventive evacuation when the available time is limited.