Géomorphologie : relief, processus, environnement, 2001 , n° 4, p. 257-270

Abridged English Version landslides occured in the ignimbrites of Charolm area and were responsible for the damming of the Layou River and The Layou River drains a mountane watershed of the Wes- one of its tributaries, the D'Leau Matthieu River. Between tern Dominica Island, West Indies. The watershed is shaped 1997 and 1999, the creation and rupture of the dams loca- into soft volcanic rocks which are sensitive to landslides and ted in the gorges of the Layou River promoted huge debris debris flows during periods of cyclonic rains. Geology, cli- flows (ca 400,000 - 500,000 m3 in November 1999) which mate and hydrology are still poorly understood which is filled the river with fine sediments till the coast. This sedi- detrimental to a sound management of the watershed which ment wave exacerbated the flooding of the valley and des- experienced severe problems since 1988. Several successive troyed the crops on the alluvial plain. Detailed observations