Deciphering sediment Connectivity Index and erosion pattern in a debris flow catchment

Understanding sediment connectivity and erosion pattern are fundamental in order to assess in a proper way actual and potential future hazard in debris flow prone areas. In this work, we propose a novel way to analyse and decipher the Connectivity Index (CI) applied in the Saint Antoine catchment, located in the French Alps. We conceptualised a procedure for the extraction of each variable involved in the CI computation along the thalweg profile. This new way to analyse CI helps to understand how this index is affected by past debris flow events and presence or absence of protection measures, also comparing protected reaches against non-protected reaches. This method opens new opportunity to use the Connectivity Index as an effective instrument to catch present or future hazard and support the planning of hazard mitigation measures.