Exposure to landslides in rural areas in Central Italy

The Total Susceptibility Index (TSI) gives the overall (total) propensity of pixels to be affected by shallow (SL) or deep-seated (DL) landslides, debris flows (DF), and rockfalls (RF), in any possible combination. For each TSI value, the corresponding values of the Specific Susceptibility Index (SSI), a four-digits positional index, is given (Table 1). By reading the SSI it is possible to understand the landslide types expected within a given pixel because it is made up by four digits, each expressing the susceptibility to the single landslide types considered. Each of the four digits is referred to as Susceptibility Index (SI), and expresses, for each pixel, the propensity to be affected by a landslide of that specific type. For all the landslide types except debris flows, SI values give the susceptibility models prediction in terms of presence (1) or absence (0) of landslides. For debris flows, the SI has four classes, depending on the combined model output. Low values show low susceptibility, and 0 show no susceptibility. For debris flows, the Susceptibility Index is equal to 4 also where DF deposits where mapped in the landslide inventory map (Map A). The Total Susceptibility is expressed by the TSI in five classes, namely Negligible, Low, Medium, High and Very High. The five classes of TSI also correspond to the five classes of exposure to landslides. Additionally to the local susceptibility conditions and exposure, for each pixel, also the morphological suitability for post-seismic rebuilding was evaluated.