GIS-based geomorphometric analysis of stream networks in mountainous catchments: implications for slope stability

This work presents the application and validation of a GIS-based toolbox called SLiX, devoted to extract Stream Lengthgradient (SL) index values along stream networks starting from Digital Elevation Models (DEMs). SL anomalous values are helpful to outline significant deviations from the concave-up shape of river longitudinal profiles of bedrock streams within mountainous catchments. The spatial analysis of SL index may be suitable for detecting along stream knickzones, supporting the investigation of the process responsible for their formation such as active tectonics, landslides interacting with streambeds or variations in bedrock resistance to erosion. The application in a mountainous catchment localized in the central Apennines (Italy) confirmed the proper functionality of the tool and the potentiality of the SL spatial analyses. This analysis has been integrated by the study of the Slope- Area (SA) function, which provided the contributing area threshold value required for the extraction of the stream network. SA analysis also supported the geomorphological interpretation of the knickzones detected through the SLiX application. The combination of SL and SA analyses in the sample area within the central Apennines revealed practical for detecting a major knickzone at a paleo-lake originated by the run-out of a rockslide. The SA function allowed interpreting the knickzone as one of the slope-break typologies, suggesting its occurrence and upstream propagation before the emplacement of the mass movement.