Taux dʼablation des falaises crayeuses haut-normandes : l’apport du scanner laser terrestre

Pauline Letortu 1, * Stéphane Costa 1 Christophe Delacourt 2 Olivier Maquaire 1 Emmanuel Augereau 2 Robert Davidson 1 Serge Suanez 3
* Corresponding author
1 LETG - Caen - Littoral, Environnement, Télédétection, Géomatique
LETG - Littoral, Environnement, Télédétection, Géomatique UMR 6554
3 LETG - Brest - Littoral, Environnement, Télédétection, Géomatique
LETG - Littoral, Environnement, Télédétection, Géomatique UMR 6554
Abstract : The most relevant point of view to quantify the regressive evolution of cliffs is the horizontal vision. This one allows to observe the whole cliff face that photo-interpretation of oblique images only partially captures. However, the fine quantification of slope dynamics by horizontal vision is only possible with the use of a terrestrial laser scanner (TLS). These measures were performed on the chalk cliffs of Upper Normandy in collaboration with the Domaines Océaniques laboratory (IUEM, Brest). Diachronic survey between 2010 and 2013 was performed, at high frequency (every 4-5 months), in order to obtain information about the production of debris every season. This study was conducted on two separate sites (context of active cliff and abandoned cliff) but lithostratigraphic characteristics are similar. With a precise protocol of topographic surveys, the accuracy of the measurement and thus the quantification of production debris is centimeter (± 0.01 to 0.04 m). The application of this technique allows to highlight the ablation rates are, unsurprisingly, 3-4 times higher in a context of active cliff than in a context of abandoned cliff.Moreover, these retreats between 2010 and 2013 are quite similar to those obtained on longer timescales (between 1966 and 2008) thanks to the analysis of erosion of chalk cliff top from vertical photographs (IGN, National Geographic Institute). Finally, the TLS allows to observe the spatial distribution of departure areas of debris. Thus, the faces of active cliffs (Petit Ailly) and abandoned cliffs (Dieppe) recede faster at the top of the slope than at its foot.
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https://hal.archives-ouvertes.fr/hal-01143688
Contributor : Serge Suanez <>
Submitted on : Sunday, April 19, 2015 - 8:07:19 PM
Last modification on : Tuesday, August 27, 2019 - 11:02:05 AM

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Pauline Letortu, Stéphane Costa, Christophe Delacourt, Olivier Maquaire, Emmanuel Augereau, et al.. Taux dʼablation des falaises crayeuses haut-normandes : l’apport du scanner laser terrestre. Géomorphologie : relief, processus, environnement, Groupe français de géomorphologie (GFG), 2015, 21 (1), pp.73-82. ⟨10.4000/geomorphologie.10872⟩. ⟨hal-01143688⟩

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