QUANTIFYING THE MORPHOLOGICAL SIGNATURE OF SLOW-MOVING LANDSLIDES IN THE EASTERN APENNINE MOUNTAINS, ITALY

This study explores whether the morphology of slow-moving landslides in the Eastern Apennine Mountains of Southern Italy can be used to infer information about the processes driving hillslope evolution in the region. We focus on the area around two hilltop towns, Volturino and Motta Montecorvino. The study area is composed of clay-rich, tectonically disturbed, highly fissured soil and rock and a more competent calcarenite rock formation. The towns are built on the calcarenite formation and most of the landslide scarps are also found in the calcarenite, whereas the toes of the landslide are generally found in the softer, clayey formations. Although hillslope movement is on the order of centimeters per year, the landslides are compromising the infrastructure of these towns.

Using previously made landslide maps and a 1 m LiDAR DEM, 97 landslides around Volturino and Motta were mapped. Of these, 40 were field verified. Morphological data for the landslides were extracted using ArcGIS. We hypothesize that landslide shape evolves through time. To examine this, the landslides were categorized based on standard deviation of body widths and aspect ratios (average width/landslide length). Slope and curvature of the landslide profiles were also calculated. We estimated an average erosion rate due to landsliding using borehole data from one of the landslides.

In general, we find that the landslides grow in an organized fashion. Data show that slope generally decreases with increasing landslide area. The scaling relationship between landslide length and area is very similar to that of fluvial networks. Landslides with higher aspect ratios are generally steeper, and as the landslides elongate and their aspect ratios decrease, longitudinal slopes also decrease. This suggests that as landslides evolve they progressively decrease the landscape gradient. Curvature data show that some profiles of landslide bodies have local concavities or convexities, but overall the profile curvature varies around zero. In other words, the slope of the landslide does not systematically change from landslide head to toe. The maximum erosion rate due to landsliding is estimated to be 0.067 mm/yr. Although this is a relatively slow erosion rate, these landslides are undermining the towns of Volturino and Motta, and have a large impact locally.