Assessment of hillslope instability hazard based on fuzzy mathematics methods

The hillslope instability forecasting by a deterministic quantification of factors inducing the geomorphologic hazard is largely spread in recent scientific literature. The sum of conventional scorings attributed to each instability factor determines the overall instability hazard. A new method for assessing the hazard using the fuzzy mathematics was carried out and applied in a pilot area of Central Apennines (Italy) at 1:100,000 scale. A map with the mapping units arranged in 4 hazard classes which agree to present and past landslides occurrence was obtained. In order to evaluate the difference between the deterministic and fuzzy approaches, a smaller sub area was selected and tested by 7 operators from different technical and scientific expertise. Results suggested that the fuzzy method is more useful for its flexibility and skill in reducing the importance of errors and appears to be well related to the landscape variability.