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Protection
of the Somme bay against river

and coastal flooding (France)

© Ault municipal council In the early 1990s, Sogreah began conducting studies in the Somme bay on issues such as
sedimentation, flood protection, coastal reinforcement and managed realignment. However,
a turning point was reached with Atlantic storm Xynthia in February 2010, when the nation
We have been working without suddenly became aware of the risks associated with coastal flooding. This extreme event
interruption since the 1990s in caused around fifty deaths and serious damage to property, and the authorities quickly realised
this coastal region, which has how fragile certain stretches of the French coast were. The outcome was the introduction of
been affected by several extreme Flood Prevention and Action Programmes (‘PAPI’), agreements signed between the State and
climatic events that generated local authorities to study risks and reduce their impacts in numerous regions.
both river and coastal flooding.
After taking part in the creation In early 2013, the Syndicat Mixte Baie de Somme - Grand Littoral Picard commissioned a
of a Flood Prevention and Action consortium led by Artelia to carry out a multidisciplinary study for a Flood Prevention and
Programme between 2013 and Action Programme covering three estuaries (the Bresle, Somme and Authie) and the river
2016, we are now supervising Somme with its tributaries. This vast area comprises 110 km of coastline and covers a total
2
the implementation of various of 180 km in more than 160 municipalities. The study led to a comprehensive summary of
measures and development the various issues facing the bay and included a detailed assessment of the stakes involved.
works aimed at improving These were examined from the technical, environmental, economic and social standpoints.
the region’s protection and A complex numerical model was built covering both the river and maritime domains. This gave
resilience. a better understanding of the phenomena at work, enabled the risks to be assessed according
to different climatic events, and helped to define the measures needed to combat river and
coastal flooding. Another part of the study concerned an appraisal of many existing structures.
After the study was finished in 2016, the Flood Prevention and Action Programme for the
Somme Bay, Authie and Bresle was approved for funding by the State and the local authorities.

In early 2020, the client demonstrated its continued confidence in Artelia by commissioning us
to provide design and construction supervision services for the works planned in the context of
the Programme (cost of works: €65m).

Sébastien Ledoux
Somme bay, Le Crotoy - France - © Altimage Project Director | Water & Africa Middle East

104 I ARTELIA, 10 YEARS OF EXISTENCE, 100 YEARS OF EXPERIENCE ARTELIA, 10 YEARS OF EXISTENCE, 100 YEARS OF EXPERIENCE I 105