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This study was prompted by the occurrence of an extreme Damaging geo-Hydrological Event (DHE) which occurred on October 25th 2011 and which affected a wide area of the northern Mediterranean region. After analysing the storm by means of the precipitation time series, the study attempts to relate the October 25th 2011 DHE with a series of other DHEs that occurred in the period 1954–2012, assessed via the use of historical data and classified according to severity, with a Storm Erosivity Indicator (Ra). The annual mean of the Ra value (2582 MJ mm ha − 1 h − 1 y − 1 ) confirmed that the study area is one of the European regions with the highest rainfall erosivity level. A shift in storminess during 1991–2012 with respect to 1954–1990 was observed. A return period of 1000 years was calculated for the single storm erosivity of October 25th, which contributed to 84% of the total annual storm erosivity of 2011 A quite good agreement was found comparing DHE distribution and severity with Ra anomalies over time. As a matter of fact, most of the low severity DHEs (62.5%) occurred in years in which the Ra was below the average value. Moreover, almost all DHEs (93%) ranging from medium- to very high-severity occurred in years for which the Ra exceeded the average value. With regard to the occurrence of the most severe DHE classes, a threshold of the Ra and a recurrence time of approximately 3300 MJ mm ha − 1 h − 1 y − 1 and 12 years, respectively, were identified. Finally, some evidences suggest that an increasing frequency of DHEs is expected in the forthcoming years. It is argued that understanding these issues is a major priority for future research in order to improve land and urban planning strategies for preserving people and the environment, leading ultimately to an effective risk reduction. [ABSTRACT FROM AUTHOR]

We investigated relations between slip-surface geometry and deformational structures and hydrologic features at the Montaguto earth flow in southern Italy between 1954 and 2010. We used 25 boreholes, 15 static cone-penetration tests, and 22 shallow-seismic profiles to define the geometry of basal- and lateral-slip surfaces; and 9 multitemporal maps to quantify the spatial and temporal distribution of normal faults, thrust faults, back-tilted surfaces, strike-slip faults, flank ridges, folds, ponds, and springs. We infer that the slip surface is a repeating series of steeply sloping surfaces (risers) and gently sloping surfaces (treads). Stretching of earth-flow material created normal faults at risers, and shortening of earth-flow material created thrust faults, back-tilted surfaces, and ponds at treads. Individual pairs of risers and treads formed quasi-discrete kinematic zones within the earth flow that operated in unison to transmit pulses of sediment along the length of the flow. The locations of strike-slip faults, flank ridges, and folds were not controlled by basal-slip surface topography but were instead dependent on earth-flow volume and lateral changes in the direction of the earth-flow travel path. The earth-flow travel path was strongly influenced by inactive earth-flow deposits and pre-earth-flow drainages whose positions were determined by tectonic structures. The implications of our results that may be applicable to other earth flows are that structures with strikes normal to the direction of earth-flow motion (e.g., normal faults and thrust faults) can be used as a guide to the geometry of basal-slip surfaces, but that depths to the slip surface (i.e., the thickness of an earth flow) will vary as sediment pulses are transmitted through a flow. [ABSTRACT FROM AUTHOR]