Profils longitudinaux et ruptures de pente : enseignements géomorphologiques en Bretagne du sud

Analysing of longitudinal profiles of coastal river channels in South Brittany allows to highlight relationships between fluvial dynamics, lithology and tectonics. Profile shapes and knickzones (high gradient sections) show that headward incision is due to tectonics, but controlled by lithology. In...

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Bibliographic Details
Published inPhysio-géo Vol. 8; no. Volume 8; pp. 49 - 65
Main Author Larue, Jean-Pierre
Format Journal Article
LanguageEnglish
Published AERES 12.01.2014
Physio-Géo
Subjects
Bretagne
Geography
headward incision
Humanities and Social Sciences
knickzones
lithology
longitudinal profiles
tectonics
Bretagne
knickzones
tectonics
headward incision
longitudinal profiles
lithology
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Summary:Analysing of longitudinal profiles of coastal river channels in South Brittany allows to highlight relationships between fluvial dynamics, lithology and tectonics. Profile shapes and knickzones (high gradient sections) show that headward incision is due to tectonics, but controlled by lithology. In little hard rocks, like Brioverian micaschists, profiles are concave- upwards and without any knickzone. While in hard rocks, such as granites or gneiss, large knickzones disrupt the longitudinal profiles. Along the north-south rivers which crosses various lithology,the upstream reaches present longitudinal profiles with high concavity and shallow incision, whereas the downstream reaches are marked by week concavity, important knickzones and deeper incision. This contrast indicates a steady state evolution in the upstream reach and a desequilibrium in the downstream reach.
ISSN:1958-573X
1958-573X
DOI:10.4000/physio-geo.3798