Data‐driven modelling of joint debris flow release susceptibility and connectivity

Abstract

In mountain basins, sediment supply to the fluvial system occurs mainly through episodic geomorphic processes-such as debris flows and other landslide types-whose effectiveness is strongly influenced by the structural connectivity within a catchment. This paper presents a novel data-driven approach to identify and map areas that are simultaneously susceptible to debris flow initiation and structurally connected to the main channel network (i.e. relevant sediment source areas for predicting and mitigating flood hazards in the river channels). The presented approach comprises: (i) the visual interpretation, delineation, mapping and classification of event-specific connected and disconnected debris flow areas in three catchments of the Italian Alps;(ii) the development of data-driven debris flow release susceptibility models that are combined with quantitatively classified index of connectivity (IC) maps; and (iii) a thorough evaluation of the approach, including an assessment of its spatial transferability across the catchments. The main results show: (i) quantitative IC thresholds to discriminate connected from disconnected debris flow release areas; (ii) statistically well-performing and geomorphically plausible debris flow release susceptibility models for the three basins; (iii) diverse joint debris flow connectivity-susceptibility maps that allow identifying zones which are differently relevant in terms of debris flow connectivity. This work also highlights the spatial transferability of the approach, associated benefits and potential drawbacks, as well as the utmost importance of a thorough combined quantitative and qualitative (i.e. geomorphic plausibility) evaluation of the underlying results. The proposed approach is rather simple and requires few basic input data, and can therefore be applied over vast areas (e.g. to support regional-scale hazard assessments or sediment management plans).

Multi‐decadal quantification of interactions between coarse sediment fluxes and channel management in South Tyrol, Eastern European Alps

“…However, relatively wide channels (high W * values) are characterised also by non‐glacial rivers draining sedimentary substrates, which are prone to occasional (i.e. storm‐driven) supply of large coarse sediment volumes by numerous debris flow tributaries (Brardinoni et al, 2012; Scorpio et al, 2022; Steger et al, 2022).…”

Channel changes over the last 200 years: A meta data analysis on European rivers

“…In the last decade, many rivers have experienced some widening. This trend has been attributed to different causes, including the local implementation of restoration projects (e.g., Ahr, Mareit, Drac rivers; Brousse et al, 2021; Campana et al, 2014; Scorpio et al, 2020) or the occurrence of flood events (e.g., Fortore, Nure, Piave, Pfitsch, Schnals, Trebbia rivers; Comiti et al, 2011; Scorpio & Rosskopf, 2016; Scorpio, Crema et al, 2018; Steger et al, 2022), which caused bank erosion, channel aggradation and overbank deposition (Krapesch, Hauer, & Habersack, 2011; Liébault et al, 2022, 2024; Lucía et al, 2018; Righini et al, 2017; Ruiz‐Villanueva et al, 2018, 2023; Surian et al, 2016).…”

Assessing multi-hazard susceptibility to cryospheric hazards: lesson learnt from an Alaskan example

“…There, the susceptibility patterns are obtained by locally solving the prediction function fitted over another study area. This procedure is commonly referred to as model transferability (Steger et al, 2022) or as validation with independent spatial data (Roberts et al, 2017) and it is often assumed to return worse performance as compared to tests that are run within the same study area where a given model is calibrated. This is confirmed even in this case, with barely acceptable transferred performances down to 0.7 of AUC in both cases.…”