Statistical and empirical analyses of the triggers of coastal chalk cliff failure. Issue 10 (7th May 2015)

• Record Type: Journal Article
• Authors: Letortu, Pauline; Costa, Stéphane; Cador, Jean‐Michel; Coinaud, Cyril; Cantat, Olivier
• Is Part Of: Earth surface processes and landforms. Volume 40:Issue 10(2015)
• Page Start: 1371
• Page End: 1386
• Publication Date: 2015-05-07
• Subjects: Geomorphology -- Periodicals; 551.4
• DOI: 10.1002/esp.3741
• Languages: English
• ISSNs: 0197-9337

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>The triggering factors of rock falls remain unknown due to a lack of exhaustive, regular and accurate surveys. Based on an inventory of 331 rock falls collected weekly between 2002 and 2009 from Veules‐les‐Roses to Le Treport (Upper Normandy), the relationships between coastal chalk cliff rock falls (dates and geomorphological features) and external factors commonly agreed as triggering (rainfall, temperature variations, tide and wind) are studied. The combination of multivariate statistical and empirical analyses indicates that (1) 'cold and dry weather' and 'high rainfall and high wind' are the conditions most likely to trigger rock falls, (2) the main triggering factors of rock falls are effective rainfall (for rock falls mostly between 200 and 1400 m<sup>3</sup> or larger than 10 000 m<sup>3</sup> and coming from the whole cliff face), freeze/thaw cycles (especially for rock falls smaller than 200 m<sup>3</sup> and coming from the foot and top of the cliff face) and marine roughness (rock falls mainly smaller than 200 m<sup>3</sup> and coming from the cliff foot). However, the contribution of each factor to triggering is difficult to determine because of combinations of factors (85% of 331 cases), relays of processes and hysteresis phenomena. In view of these first results, it is still presumptuous to predict the location and time of triggering of rock falls. However, the statistical and naturalistic approaches adopted and the observations made in this study are from an original database, and constitute a real starting point for the prediction and prevention of the hazard of coastal chalk cliff rock falls in Upper Normandy. Copyright © 2015 John Wiley & Sons, Ltd.</p> </abstract>