**3. Methodological assessment**

To complete researches that have been already carried out on the 2018 Montecito event [5, 35–39], the deterministic cellular automaton so-called RuiCells© was used.

**Figure 2.** *Damage and spatial extent of debris flows in 2018 in Montecito.*

First, to further assess the dynamical influences of morphological conditions on the sudden hydrological responses of the catchments located upstream of alluvial fans. Any morphometric parameters have been reported to be related to debris flow potential [25, 26], but their usefulness is limited and often criticized [27]. Second, to track the points in upstream of which areas and networks are well organized (the so-called "cauliflower effect"). Simulations give a picture of the "*width function area*" [25, 27], but concentration area or internal efficiency can be detected, and this effect could explain violent hydrological responses, in time and space.
