Identification of soil redistribution using Cs-137 for characterizing landslide-prone areas: a case study in Sarno-Quindici, Italy

Debris flows are among the most hazardous and unpredictable processes whose hazard evaluation requires an understanding of the processes that govern sediment supply, sediment bulking, flow volume, and deposition. In line with this challenge, we estimate the net soil redistribution rates in an area characterized by recurrent instability phenomena using Cs-137 as a tracer for monitoring soil dynamics. An extension of this method by applying it to the case of major landslides is addressed. Specifically, surveys of soil Cs-137 content at sites in the Pizzo d'Alvano massif (Italy), where a set of particularly damaging landslides occurred on 5-6 May 1998, are reported. Being this region prone to debris flows, two zero-order basins are examined, one of which experienced a landslide event. In that basin deposition is observed, whereas the other shows a net loss of soil. These results appear to be relevant, particularly because the rate of hollow filling could be correlated with the magnitude and/or frequency of debris flow occurrence or with some measure of the hazard presented by individual gullies.