## 2 Study Area  
The modelling framework was calibrated and tested within the Mesima stream catchment, located in the southwestern portion of the Calabria region (South Italy), between 4,284,943 m N and 4,262,983 m N of latitude and 590,786 m E and 615,866 m E of longitude (Figure 1a). The catchment covers a surface of 173.5 km\({}^{2}\) with an altitude varying from 42 to 939 m. a.s.l. (Figure 1b). The drainage network is well developed, showing a hierarchy equal to the seventh order with a sub-dendritic drainage pattern and a hyposymetric curve with a concave-convex shape indicating a high predisposition to undergo intense denudation processes [36].  
Climatically, the catchment is affected by a Mediterranean climate, with mild and wet winters and hot and dry summers. The total annual rainfall ranges from 785 to 1572 mm, with a mean yearly precipitation of approximately 973 mm. The maximum rain usually occurs in January and December, while the minimum is between July and August.  
Geologically, the study area is situated in a tectonic depression named Mesima graben, which constitutes the middle portion of the Calabrian-Peloritan Arc [37; 38]. The graben is bounded by NE-SW trending normal faults and filled by Ploi-Pleistocene marine and continental deposits, which cover the Paleozoic crystalline-metamorphic rocks or the Miocene sedimentary rocks [36; 37]. Palaeozoic crystalline-metamorphic rocks of the Capo Vaticano promotory and the Serre Massif, respectively, bound the western and eastern graben flanks [36; 37; 39].  
The lithology in the Mesima catchment is mainly dominated by Pliocene silty clay deposits and secondarily from Pliocene sand, sandstone deposits, and conglomerate of Pleistocene. Locally, evaporitic limestones (Miocene in age) overlain in discontinuity in the gneiss and granite of the Paleozoic basement are intensely fractured and weathered [39; 40]. Intense weathering processes due to marine aerosol also affect sedimentary deposits, mainly  
Figure 1: (**a**) Location map of the study area; (**b**) spatial distribution of the gullies and drainage network on a digital elevation model of the Mesima stream catchment.  
those close to coastal areas [41]. In some areas, eluvial-colluvial deposits (Holocene) overlay the sedimentary rocks or, directly, the crystalline-metamorphic rocks. Finally, Holocene alluvial deposits dominate the valley floors.  
The morphology of the landscape is characterised mainly by hillslopes with undulating sharp and rounded slopes, generally with V-shaped valleys. The latter only assumes a more concave form when colluvial deposits partly fill them. The slope gradient ranges from 0\({}^{\circ}\) to 77\({}^{\circ}\), with an average value of about 13.7\({}^{\circ}\). Badlands often affect the silty clay slopes because of water erosion caused by ephemeral streams. Instead, more competent rocks (sandstone and/or conglomerates) locally generate high-gradient slopes or sub-vertical escarpments involved in widespread landslides [36; 42]. The catchment is boarded by terrace surfaces in the upper and middle sectors, representing the relics of old fluvial terraces [36; 37]. Quaternary tectonic activity [37] shaped landforms, giving rise to a dense drainage network characterised by deep and narrow valleys with steep and bare slopes.  
From a pedological standpoint, according to the USDA classification [43], the most common soils in the study area are mainly Inceptsoils and Entisoils and subordinately Alfisoils [44]. Soil depth ranges from shallow to moderately deep (20 to 120 cm) and soil profiles are usually characterised by A-Bw/Bt-Cr and/or A-Cr/R horizons [44; 45].  
Geomorphic processes, such as landslides and water erosion processes as sheet, rills, and gullies, contributed to the catchment landscape evolution and currently represent the main controlling factor of its morphodynamics [36; 42].