Coastal cliff falls and triggering factors in Upper Normandy: spatial, temporal, and statistical approaches

Abstract : The coastline of Upper Normandy (France) is made up of a 130 km long chalk cliff in the central part of the English Channel shoreline. For the last 30 years the average chalk cliff retreat rate is about 0.21 m/y. This cliff retreat changes from location to location, and its rate can reach a metric value. Due to cliff falls threatening settlements close to the coastline, better understanding of this rocky coast erosion is greatly needed. The primary aim of this study is to determine the triggering factors of coastal chalk cliff retreat. This study is carried out in collaboration with the ESTRAN non-profit corporation that has made a weekly inventory of cliff falls (location, volume and dating) from Saint-Valéry-en-Caux to Le Tréport. Based on this unique and considerable database of 332 cliff fall events from 2002 to 2009, many analyses were made: spatial and temporal distributions of coastal cliff falls and statistical analyses of the relationship between processes and cliff falls. Coastal cliff falls occur predominantly in winter but can also occur in summer and are mainly located at the Ailly Cape. Annual return periods according to cliff fall volume were calculated. The statistical analyses point the difficulty to identify the key-processes that trigger coastal chalk cliff falls. Indeed, numerous combinations of factors and the phenomena of process shifts or even hysteresis effects make the connection between triggering agents and cliff falls more complex.
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Contributor : Pauline Letortu <>
Submitted on : Wednesday, May 16, 2012 - 12:13:46 PM
Last modification on : Friday, October 18, 2019 - 2:54:05 PM

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  • HAL Id : hal-00697841, version 1

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Pauline Letortu, Stéphane Costa, Jean-Michel Cador, Olivier Cantat, Olivier Maquaire, et al.. Coastal cliff falls and triggering factors in Upper Normandy: spatial, temporal, and statistical approaches. Colloque Journées 'Aléa gravitaire', Sep 2011, Strasbourg, France. pp.169-173. ⟨hal-00697841⟩

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