19 October 2020
Knowledge of flood risk is important to the flood forecasting process: there is no use making flood predictions for areas with low flood risk. On the other hand, higher risk locations require extra attention. Now that we are living in “unprecedented times,” the concept of risk has also become important in our personal lives.
To get an idea of the likelihood we could be infected by COVID-19, my family attempted to conduct a risk assessment. A commonly-used approach would be to simply count the number of people we are regularly in contact with. Although I am no health expert, I do know something about risk. In this case, the risk of infection is not only based on the number of interactions, but also on the probability the other person is ill, the probability that that person is contagious, and the probability of transmission. There is probably much more to this calculation, but, well, I’m not a health expert. Counting people to assess COVID-19 risk is comparable to estimating flood risk based on whether rain has fallen somewhere in a catchment. But as we all know, flood risk depends on so much more, including factors that are hard to determine. Ultimately, we concluded that without more knowledge on these risk factors, it is not possible to determine the risk of infection. So we should just limit interactions and wear face masks.
Flood forecasters, fortunately, have much more data available. Floods are rarely unprecedented. Detailed hydrological models are embedded with historical knowledge that describes the parameters of the modelled process. Remote sensing technology and increasingly high-resolution imagery greatly add to the information available to flood forecasters. New approaches make it possible to make detailed impact-based forecasts.
Interestingly, health turns out to be one of the elements that defines flood impact. People might survive a flood, but the ensuing direct and indirect impacts on health can be vast. With COVID-19 still spreading, the health factor in flood forecasting has only become more important. If you evacuate large groups of people for a flood event, and a few are carrying the virus, the consequences could be huge. Even if the likelihood of a flood remains the same, the impact, and thus the risk, has increased. This emphasizes the urgency for accurate and timely flood forecasts.
If there is a silver lining to COVID-19, it is that remote meetings and conferences have suddenly become the new normal. So please join us during the online International Delft-FEWS User Days in November, where we will discuss the latest advances in flood forecasting. You won’t have to enter high risk zones, such as conference rooms, but we will miss chatting with you in the cozy indoor pubs of the beautiful city of Delft.
ir. Arnejan van Loenen