Experimental study of the variability of sediment transport processes under outburst flood conditions in mountain streams

International audienceTo date, little is known on the features of sediment transport processes that can be triggered by an outburst flood for given field conditions. We present the results of 94 experiments carried out in a 5.0 m-long, 0.2 m-wide flume, mimicking the conditions of outburst floods on steep slopes, where water is suddenly released upstream of an erodible bed constituted of sand. Investigated slope gradients cover the range 1.7 to 38.0 %. Flow features are qualitatively analysed using pictures taken by video cameras. We emphasize analysis of the flow front features, and internal shear inside the flow. At gentle slope, the wave propagation is mainly constituted of water with limited sediment transport. When increasing the slope, a series of processes areevidenced, and lead to very concentrated rapid mass flows. We try to classify the observed flows in reference to well-known field phenomena. We finally suggest a continuum of sediment transport processes from bedload to debris flows

Experimental study of the variability of sediment transport processes under outburst flood conditions in mountain streams

International audienceTo date, little is known on the features of sediment transport processes that can be triggered by an outburst flood for given field conditions. We present the results of 94 experiments carried out in a 5.0 m-long, 0.2 m-wide flume, mimicking the conditions of outburst floods on steep slopes, where water is suddenly released upstream of an erodible bed constituted of sand. Investigated slope gradients cover the range 1.7 to 38.0 %. Flow features are qualitatively analysed using pictures taken by video cameras. We emphasize analysis of the flow front features, and internal shear inside the flow. At gentle slope, the wave propagation is mainly constituted of water with limited sediment transport. When increasing the slope, a series of processes areevidenced, and lead to very concentrated rapid mass flows. We try to classify the observed flows in reference to well-known field phenomena. We finally suggest a continuum of sediment transport processes from bedload to debris flows

L'étiage 2020 dans les Gardons amont (Cévennes) Projet pilote de suivi des débits d'étiage Rapport sur huit stations temporaires d'étiage et deux stations pérennes Janvier 2021

Convention et avenant en date du 4 juin 2018 entre le EPTB Gardons et Avignon université (UMR ESPACE) sur l'installation et le suivi de stations d'étiage dans les Gardons de 2018 à 2020