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Impact of extreme events on long-term erosion

It is now well known that rare but extreme events like storms or hurricanes play a major role in long-term erosion, but their contribution has not been precisely quantified yet. By studying erosion in tropical volcanic islands, where lithology is roughly uniform and easily dated, we have quantified erosion rates over 3 different timescales. In Basse-Terre (Guadeloupe, France), sediment transport occurring over yearly floods amount to an equivalent erosion rate 5.10-4 mm/y over the whole island. A moderate hurricane, happening in average every 5 years, contributes to  a 100 times higher erosion rate. These rare events are can therefore be held as solely responsible for the erosion rates measured over longer timescales.

(A) Elevation map of Basse-Terre on which the main watersheds are delineated. ...

Participants: P. Allemand, S. Passot, P. Grandjean, V. Langlois.
Collaborations: A. Quiquerez (U. Bourgogne), network ObsErA (Antilles) & Erorun (Réunion).
References: Allemand et al., Geomorphology (2014).