Flash floods across Europe act as reminder of an intense, rapid-onset hazard
Natural hazardsArticleOctober 15, 2018
Our thoughts are with the many residents and tourists who have been affected by the recent flash flood events in Mallorca last week as well as those affected in other locations across Europe just today. It is a stark reminder of a hazard that has very little advance warning as a flash flood can develop rapidly and brutally following intense rainfall, often over a very local area.
There are similarities to the fatal flash floods in Southern Germany in 2016 that we analyzed in one of our PERC reports. I have summarized some of the learnings here that apply to any area similar in topography / terrain that is subject to flash flooding:
- Natural watercourses have often been put in a man-made channel that is supposed to keep us safe. Going forward, we must realize the limits of this concept and that protection structures can, and often will, be overtopped and watercourses will break out of their artificial channels.
- It is difficult to provide an early warning for flash floods. Often a warning cannot be triggered until the flash flood has started upstream. This short warning time can only be a measure of last resort to save lives. We need to improve our forecasting of local intense weather events and link this to early warning systems.
- New technology should be used to generate flash flood hazard maps. Intense precipitation and flash floods depend on certain spatial factors. Technology can be used to generate flash flood and (urban) surface flood maps. There are already successful examples of this approach used to map larger river systems.
- We need to raise awareness of all those at risk from such a hazard. In the present case in Mallorca this may have been particularly difficult as tourists are unlikely to be familiar with the area and the hazards that come with it. There are two things to learn here:
(1) There are many shared responsibilities, and when we travel we need to be more aware of our surroundings and how to be safe, we can't expect to fully rely on someone else.
(2) Any warning system needs to ensure it can reach visitors that may speak various languages. A good example are easy-to-understand push messages to any cellphone currently logged on to a cell tower in the corresponding area, something I have experienced myself traveling abroad - a really good and simple measure to alert everyone.
Finally, one further way to raise awareness is to change our terminology. A “100- year flood” is often mistakenly interpreted as a flood of a magnitude that will not occur again for another century. People need to understand that, in fact, it means that there is a 1 percent chance of a flood that size occurring every year. Our terminology can be misleading – so let’s change it.