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Post-event measures: Improve education on floodhazard and flood risk

To be ready to deal with flood hazards requires ongoing education. Too often the memories of the last flood fade quickly. People who are aware of flood risks and how to reduce them are a more receptive audience. There is also a general misconception about flood probabilities or flood return periods. This is true in particular when it comes to the risks attached to events with a low probability. Research has shown that people will repeatedly tend to ignore or misinterpret small probabilities, which affects their perception of flood risk and whether it is a good idea for them to look for ways to protect property and assets. We believe that people understand the chance of an ‘annual occurrence’ better than return periods, which seem to imply an event will only reoccur after a certain number of years. Having experienced a flood, people are tempted to assume that a major flood is unlikely to affect them again in the near future. Thus, instead of referring to a ‘100-year flood,’ it would be better to provide statistical probabilities that do not imply how soon an event could happen. In the German state of Saxony, all major watersheds have witnessed an extreme flood event in recent years. Terminology should be simplified, to focus on the chance of a particular event occurring each year. Having a 10-percent chance of a flood happening in any given year would therefore banish some of the false sense of security that because a ’10-year’ flood happened in one year, it will not happen again for another decade. In the state of Saxony, authorities were blamed for not explaining following the 2002 flood that another flood of similar magnitude could happen again so quickly. Making it explicitly clear that there is a chance every year for a major flood, some people might have thought twice before rebuilding in the way they did.

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