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THARMIT Résumé de rapport

Project ID: EVG1-CT-1999-00012
Financé au titre de: FP5-EESD
Pays: France

Torrent hazard control - Attempts to elaborate models for debris flow magnitude-frequency

Hydro-meteorological parameters were analysed in order to identify possible relationship between them and debris flow events in order to contribute ro the elaboration of models for debris flow magnitude-frequency prediction.

Different threshold values of rainfall intensity to predict the occurrence of catastrophic debris flows and to identify return periods were tested in the Arbonne catchment.

Several types of triggering conditions were identified, as sufficient conditions:
- A two-days heavy rainfall (higher than 60mm/2 days),

- A two-days storm heavier than “the mean storm value + 4* standard deviation storm value” (summer period),

- A threshold where the 20 days rainfall amount is associated to a following intense 2 days rainfall event,

- A criterion where a temperature sudden change (snowmelt period) is associated to a rainfall event.

As a matter of fact, it appears that due to the various processes of initiation and mobilization processes, of course the triggering conditions are very different. In a given catchment, where various source areas and the corresponding initiation and mobilization processes exist, several different types of threshold values can operate, being related to the intensity or/and duration of a rainfall event, to the antecedent status of soil before a rainfall event or to snowmelt conditions associated to a particular rainfall event.

Up to now the question of models for debris flow magnitude-frequency prediction is improved but not solved.


Roger COJEAN, (Professor)
Tél.: +33-1-49329088
Fax: +33-1-49329128