The deaths of at least 189 people and the hundreds more unaccounted for in western Europe following the catastrophic flooding last week is a truly devastating event. The scenes of walls ripped out of houses, cars floating down streets and people in tears surveying the remains of their possessions serve as a stark reminder of the power of water.
What is most upsetting though, is that the scale of this event came as a surprise to some governments and parts of the public. It shouldn't have been like that. Scientists know that climate change is increasing the frequency of extreme weather events. We see evidence of that every day with heat waves, wildfires, droughts and storms filling the news, and flooding is no exception. It was not unfathomable that a flood event of this scale and magnitude would occur in Europe.
Luckily, we are not powerless against floods, thanks to recent scientific and technological advances, and we have excellent forecasting capabilities. This means we do not have to wait until the rain starts falling to take action.
The experiences in Germany, Belgium and the Netherlands illustrate what emergency planners have known for a long time: It is easier, cheaper and more effective to take action in advance of a flood occurring. The heavy rainfall in Germany was forecast by the weather services. Meteorologists knew what was coming several days in advance and issued weather warnings.
Early indications of serious flooding were given by the European Flood Awareness System (EFAS, part of the Copernicus Emergency Management Service) and messages were sent to relevant organizations in each of the affected countries. One of the difficulties is that the response system across Europe is fragmented, with organizations having different responsibilities across different countries. Nevertheless, there should have been time to prepare, yet the reality was that in some regions people were not evacuated until there was already water in their houses.
In the initial aftermath of the event, a spokesperson for Germany's meteorological service, the Deutscher Wetterdienst (DWD), said it had passed the flood warnings to local authorities and they, not federal agencies, were responsible for initiating evacuations or other on-site measures. Despite the scientific advances, there is clearly still a need to improve how flood warnings are communicated and to establish who is responsible for taking action and alerting the public.
This is not to say only these governments are to blame. This event could have occurred anywhere, and I suspect the warning system in other countries would have been found to have similar weaknesses. Unfortunately, it often takes a massive event to highlight the need for change.
So, what went wrong? Well, any flood warning system is only as good as its weakest link. If action is not taken on the basis of the warnings, then having excellent forecasts does not help anyone. There are potentially three main reasons why action was inadequate in this case. Either the message didn't get to the right people, it was the wrong message, or the message got through but no one believed it. In reality it was probably a mixture of all three.
Events like this one are extreme and rare. They (usually) do not happen more than once in a lifetime, so even if you live close to a river, if you have not been flooded before it is difficult to appreciate the potential devastation. Flood warnings need to bridge this awareness gap by highlighting the severity of the risk.
One limitation is that warnings are too often focused solely on what the weather will be. A warning of 150mm (6 inches) of rainfall over two days doesn't mean a lot to most people. What does mean something is a warning that gives details of what the weather will do, for example that "river levels will rise rapidly causing widespread flooding. Damage to roads and property is expected." This is often known as an impact-based forecasting.
Having been responsible for issuing and developing flood forecasts and warnings myself and working closely with the organizations that use those warnings, both in a national context when working for the Scottish Environment Protection Agency and through the University of Reading's work to support the international humanitarian response to major cyclones, I know firsthand that when big events such as this are seen in the forecast, the initial thought can be "surely that can't be right."
Organizations do not want to get it wrong. In Italy, six scientists and a government official were convicted of manslaughter and sentenced to six-year prison terms for underestimating the threat in a 2009 earthquake warning. The scientists were later exonerated and the official's sentence reduced.
There is also valid concern that if warnings are issued too often and no impacts occur, they will start to be ignored. All of this can lead to a tendency to wait until the next forecast update before issuing warnings, which reduces the time available to take action.
One question I've been asked a lot this week is what action should have been taken. In this case, there should have been earlier evacuations. There was no way to protect people against that amount of water and the priority should have been to get everyone out of harm's way. In some regions this did happen, but not everywhere. For smaller events, the response might be to install temporary flood defenses, to bring in extra staff to deal with an expected rise in call-outs, and to take personal responsibility for moving your valuables and pets to a safe place.
Evacuating people is a difficult decision. It is costly and there is a risk that some people (particularly the elderly and vulnerable) will die while being evacuated. To take that decision requires confidence in the forecast. My research and the work of many others (for example through the World Meteorological Organization HIWeather program) show that one way to build this confidence is to make sure that everyone involved in the forecasting chain, from weather forecasters, hydrologists, decision makers and local communities, are involved in the design of the flood warning system from the start.
Those conversations should happen in "peace time" so that everyone understands each other's responsibilities during an event. Furthermore, the strengths and limitations of the forecasting models can be openly discussed. It is a process that is increasingly being called co-production. This integrated approach means that decisions can be made in advance to balance the risks, rather than in the heat of the moment.
An effective flood warning system alone will not reduce all impacts from flooding. Flood defenses are essential to protect many urban areas, but it is not practical to build them everywhere. We should be building more resilient communities with space for water alongside people and properties that can quickly be dried out and lived in again after floods. We should also be raising awareness among the public about the current and increasing risk of flooding. Flood warnings are, however, an important part of an integrated flood risk management plan. By making sure that the right people have the right information at the right time, lives can be saved.
It is unfortunate that it often takes a major event to act as a catalyst for change, but the experience in Europe has opened up a valuable opportunity for the international disaster management community to reflect on how prepared we really are for more frequent extreme events. There are many lessons to learn that I hope will improve our preparedness for floods and other disasters, both now and in the future.
Linda Speight is a hydrometeorologist at the University of Reading. Her research seeks to inform the development of effective flood forecast and warning systems by improving integration between science and end users. The views expressed here are her own.