In 1910 Paris faced a very big flood, which it had not seen for hundreds of years. How can these catastrophes occur and how can a city prepare for the unexpected?

In France many rivers flow towards the Île de France and unite shortly before it, so that floods can fairly easily be dangerous if only few of these rivers have slightly more water. But exceptional overflow can be caused through water saturated soils (as in 1910), underground water in excess and flood of the entire river system. Factors that make it worse are urbanisation, mineralisation of the river’s sides that increase the speed of floods, agricultural processes making soils waterproof an climatic discordance.

The city administration is trying to prevent such catastrophic floods in future by trying to forecast and announce dangerous situations through information and data sharing. The water level of 1910 has since then been the reference level for any prevention plan, because if a similar flood as in 1910 would occur in 2010 many damages would be the same, but with many more people affected by it, due to the city’s enormous growth.

The city’s preparation plan consists of warning and informing the population about possible risks, taking preventive measures, establishing procedures, acquiring crisis equipment and training staff to be prepared. The aim is to get the maximum amount of data and to use predictive computer simulations, to transmit information as far as possible to all actors involved and to react in integrated ways with all levels of government. If all these preparation helps in reality can only be proofed in case of emergency, in a case of another centennial flooding since today, people are far more dependent on technology and therefore far more vulnerable than in 1910.