Abstract
A method to predict the most probable flow rheology in Alpine debris flows is presented. The methods classifies outcropping rock masses in catchments on the basis of the type of resulting unconsolidated deposits. The grain size distribution of the debris material and the depositional style of past debris flow events are related to the dominant flow processes: viscoplastic and frictional/collisional. Three catchments in the upper Susa Valley (Western Alps), characterized by different lithologies, were selected for numerical analysis carried out with a Cellular Automata code with viscoplastic and frictional/collisional rheologies. The obtained numerical results are in good agreement with in site evidences in terms of depositional patterns, confirming the possibility of choosing the rheology of the debris flow based on the source material within the catchment.
Highlights
Debris flows are rapid to very rapid flows of sediment water mixtures, with high solid concentration (Jakob and Hungr, 2005)
The obtained numerical results are in good agreement with in site evidences in terms of depositional patterns, confirming the possibility of choosing the rheology of the debris flow based on the source material within the catchment
The constitutive law implemented for the analysis is very simple, the use of a viscoplastic rheology in Excellent Clay-Maker (ECM) catchments seems to capture the macroscopic features of real events
Summary
Debris flows are rapid to very rapid flows of sediment water mixtures, with high solid concentration (Jakob and Hungr, 2005). As these natural phenomena are among the most dangerous and destructive events, the definition of runout scenarios for risk assessment has received wide interest in recent decades. During rainstorm events catchments can be subject to debris flows along their channels At this scale a quick and simple procedure of runout assessment can be useful for hazard mitigation. The estimation of runout is generally performed by numerical modeling To this end, the identification of the rheology of the mixture is required in order to choose the most appropriate constitutive law to be used in debris flow simulations. Very roughly debris flow behavior can be subdivided into two basic main types (Coussot and Meunier, 1996): viscoplastic (high fine content material) and frictional/collisional (coarse material with low fine content)
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