Open AccessDebris-flow functioning and their contribution to sedimentary budgets: the Peynin subcatchment of the Guil River (Upper Queyras, Southern French Alps)
Author(s) -
Vincent Viel,
Monique Fort,
Candide Lissak,
K. Graff,
Benoît Carlier,
Gilles Arnaud-Fassetta,
Étienne Cossart,
Malika Madelin
Publication year - 2018
Publication title -
la. landform analysis/landform analysis
Language(s) - English
Resource type - Journals
eISSN - 2081-5980
pISSN - 1429-799X
DOI - 10.12657/landfana.036.007
Subject(s) - tributary , sediment , hydrology (agriculture) , context (archaeology) , drainage basin , debris flow , flood myth , sedimentary budget , erosion , debris , environmental science , geology , hyperconcentrated flow , sediment transport , geomorphology , bed load , geography , paleontology , oceanography , cartography , geotechnical engineering , archaeology
The Peynin catchment (15 km2) is prone to catastrophic floods (June 1957 – Recurrence Interval R.I.>100 yr), June 2000 (R.I.-30 yr) with serious damages to infrastructure and buildings located at the outlet. In this paper, PIT tags tracers and Vensim modelling software are used to better assess the sediment delivery unsteadiness, and more specifically to evaluate the respective role of geomorphological processes on sediment supply during flood event. For the last 20 years, our results highlight a significant variability in sediment delivery from a tributary to another one. According to our studies, we suppose that two torrential tributaries of the Peynin river, the Peyronnelle and Three Arbres subcatchments (<2 km2, representing <15% of the Peynin catchment area) are responsible of 80% of the sediments observed at the outlet of the catchment. Several processes take a part of these sediment transfers, but the efficiency of the sediment cascade in this catchment can be explained by a strong connectivity between sediment erosion area and the main channel of the catchment. Debris and torrential flows triggered during high intensity meteorological event are actually effectively coupled in space and time and guarantee an important sediment supply able to reload the downstream part of the sediment cascade. Recent climate trends, marked by extremes, suggest consequently more damaging events to come, in a context of increasing vulnerable assets