{"id":2680,"date":"2022-11-24T14:52:46","date_gmt":"2022-11-24T13:52:46","guid":{"rendered":"https:\/\/ingenius.ecoledesponts.fr\/?p=2680"},"modified":"2025-07-29T15:03:51","modified_gmt":"2025-07-29T13:03:51","slug":"flooding-cities-must-adapt-and-become-resilient","status":"publish","type":"post","link":"https:\/\/ingenius.ecoledesponts.fr\/en\/articles\/flooding-cities-must-adapt-and-become-resilient\/","title":{"rendered":"Flooding: cities must adapt and become resilient\u00a0"},"content":{"rendered":"\n\n\n
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X-band and dual-polarization radar acquired by the School with the help of the “Hydrology for a Resilient City” Chair, supported by Veolia, the European RainGain project and the regional RadX@IdF project (\u00a9Pachourse pour HM&Co).<\/figcaption><\/figure>\n\n\n\n

\u201cIt is quite unique that a heavy rainfall event, or even a simple shower, fairly commonplace meteorological events, are still poorly characterized scientifically. The dynamics of precipitation, due to its particulate and non-linear nature, remain a complex phenomenon to describe at the theoretical level and therefore difficult to anticipate\u201d, he explains. This is a vast field of research based on the famous Navier-Stokes equations, obtained for the first time two hundred years ago by Henri Navier<\/a>, a prominent figure in the history of the \u00c9cole nationale des ponts et chauss\u00e9es, but whose existence and regularity of solutions remain one of the great unsolved mathematical problems. The Nobel Committee for Physics recently recalled the issues associated<\/a> with these questions.<\/p>\n\n\n\n

Precipitation: significant impacts on the environment<\/strong><\/h2>\n\n\n\n

In addition to the theoretical study of intermittency in precipitation and other fields of geophysics, this researcher, who has assumed leading responsibilities in American, European and international learned societies, has become increasingly interested in its impact on our environment, particularly urban space and its resilience. “This is what we wanted to explore in 2010 when we created the Hydrology for the Resilient City chair with Veolia. The theme was unusual at the time. Today, it goes without saying. Our approach is holistic and much more integrative than traditional urban hydrology,\u201d he says. For example, the aim is to better understand the local dynamics of precipitation and how the formation of millions of drops of water can result in sometimes violent downpours and ultimately in floods. \u201cWe are thus trying to better anticipate the interactions between water, atmospheric dynamics and the response of the environment in terms of runoff, absorption and evaporation capacity, or, in extreme cases, flash floods,\u201d explains Daniel Schertzer, who was a researcher at M\u00e9t\u00e9o-France.<\/p>\n\n\n\n

From research to concrete applications<\/strong><\/h2>\n\n\n\n

Within the framework of the Chair with Veolia, several types of research have been carried out. Some are in the field of physics and mathematics, others are geared towards application. \u201cWe have become strongly interested in X-band and dual-polarized radar technology. This technology allows a measurement of precipitation at a resolution ten times higher than the usual one kilometer with much more compact radars. In the early days of the Chair, this technology had not been widely explored, except in Japan, where we participated in the TOMACS program, which became international with the support of the World Meteorological Organization,” he notes. The project was conducted within the framework of the European “RainGain” project, for which the School was the French coordinator, and resulted in the installation of a radar on the roof of the school (http:\/\/www.raingain.eu\/en\/node\/4619).. It has not only led to progress in the apprehension of precipitation dynamics within a short range (one hundred meters), but it has also allowed us to explore the chain of values associated with this improvement in resolution. This is the case with the development of Multi-Hydro, a model integrating various components of the water cycle at very high resolution, and the RadX “Software as a Service” platform open to the general public and professionals alike. One of its applications is forecasting the very local impact of precipitation, for example during events such as the 2024 Olympic Games in Paris, a current <\/a>World Meteorological Organization project in close synergy with M\u00e9t\u00e9o-France, particularly with a view to protecting athletes, spectators and infrastructure.<\/p>\n\n\n\n

Six consecutive X-band and dual-polarization radar measurements of the \u00c9cole nationale des ponts et chauss\u00e9es<\/h3>\n\n\n\n
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Six consecutive X-band and dual-polarization radar measurements of the School (from 7:58 to 8:15 am on February 3, 2021, between two Meteo-France images, with a radial resolution of 128 meters) of a thunderstorm event with intense and very intense cores \u00a9 HM&Co, 2021<\/figcaption><\/figure>\n\n\n\n

Adapting to better resist<\/strong><\/h2>\n\n\n\n

“We are acquiring knowledge, modeling these complex systems, developing innovative observation technologies, and more. All of this makes it possible to make decisions, to react more quickly, and to better design and therefore reduce the fragility of our urban systems, for example in the face of the risks of network congestion and urban flooding,” notes Daniel Schertzer. The link between this research and the concept of resilience is therefore clear. \u201cThis ancient notion (used by Cicero, even) can be succinctly defined as the capacity of a system to ensure its sustainability by adapting to destabilizing elements. In this regard, the terrible example of New Orleans hit by Hurricane Katrina in 2005 comes to mind. A disaster whose effects in terms of human and economic development are still being felt today,\u201d points out the man who organized a meeting of geophysics experts in New Orleans twelve years after Katrina.<\/p>\n\n\n\n

In France, these issues are, unfortunately, often highlighted during the Cevennes episodes or the heavy autumn rains in the South-East of France, with the associated material and human damages, as in the V\u00e9subie valley (Alpes-Maritimes). How can we prevent this damage? “The idea shared today in hydrology is to no longer try to manage the risk, but to try to reduce it and especially to increase resilience. However, there are many unknowns, which brings us back to our theoretical work, but also to the problem of urban development.”<\/p>\n\n\n\n

Towards a new conceptualization of cities<\/strong><\/h2>\n\n\n\n

According to Daniel Schertzer, this paradigm of resilient cities, which can rely on nature-based solutions, would require a profound rethinking of the very management and design of our cities.<\/p>\n\n\n\n

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