Storyline of the winter 2023/2024 flood events in Nord-Pas-de-Calais (France)

During the winter of 2023/24, northern France experienced two consecutive flood events that caused severe losses and damages in the region. Although the region is well-known for being exposed to flooding, the impact of these events was much greater than that of previous floods. Hundreds of municipalities were declared damaged while hundreds of houses were flooded. Some places and people were flooded twice during the winter. 

This work aims to understand the physical and societal conditions that led to these impacts. We conduct an event-based storyline to investigate the flood hazard, the exposure of the inhabitants of the territory and their vulnerability (Sillmann et al 2020). The approach allows us to denaturalise disaster (Klinenberg, 1999) by studying the links between hazard and impacts, but also between exposure, vulnerability and impacts. This is done by combining various datasets. 

The hazard analysis is based on long-term meteorological and hydrological observations. This enables us to identify the hydro-climatic drivers of the flood. We show it is the combination of the succession of eight storms and almost continuous rain during winter 2023/24 that led to extreme rainfall accumulation. The study of winter weather regimes based on ERA5 data explains the persistence of those drivers. Using Mann-Kendall statistics, we demonstrate that the hydro-climatic drivers observed during the flood events fall within a long-term trend towards higher average and extreme precipitation in Nord-Pas-de-Calais. We investigate the compound nature of the 2023/24 flood events (Zscheischler et al 2020). The succession of eight heavy precipitation events leading to two flood events emphasises the temporarily compound nature of the events. In addition, we explore the multi-variate compoundness of the event, through observations of the high tidal coefficients, the land use and land coverage during winter 2023/24, which can all be partly responsible for the flooding.

Finally, we use past flood events as milestones to compare to 2023/24 flood events, to better understand the drivers, both meteorological and non meteorological, which led to such extreme flooding.

 

Klinenberg, Eric. s. d. Denaturalizing Disaster: A Social Autopsy of the 1995 Chicago Heat Wave.

Sillmann, Jana, Theodore G. Shepherd, Bart van den Hurk, et al. 2021. « Event-Based Storylines to Address Climate Risk ». Earth’s Future 9 (2): e2020EF001783. https://doi.org/10.1029/2020EF001783.

Zscheischler, Jakob, Olivia Martius, Seth Westra, et al. 2020. « A Typology of Compound Weather and Climate Events ». Nature Reviews Earth & Environment 1 (7): 333‑47. https://doi.org/10.1038/s43017-020-0060-z.