Influences of hydrological and hydrogeological conditions on debris flows in peri-vesuvian hillslopes

Abstract

Abstract. The paper illustrates some results of research carried out to assess factors triggering debris flows which involve the pyroclastic overburdens covering carbonate mountains around Vesuvius. The aims of the research were to reconstruct a relationship between rainfall and debris flow occurrence and to highlight empirical hydrological thresholds through rainfall pattern analysis. The research was also aimed at investigating hydrogeological features of a pyroclastic cover-carbonate bedrock system to analyse factors inducing temporary hydraulic flow, critical for pyroclastic soil stability. The results of research are the following: i) rainfall pattern highlights empirical hydrological thresholds that differentiate the Lattari and Salerno Mountains from the Sarno Mountains; ii) in some sample areas of the Sarno Mountains close to the trigger zones of the landslides of May 1998 strong variation in hydraulic conductivity has been found in the first few meters below the surface; iii) these permeability variations would seem to justify temporary perched water tables that might affect the stability of the pyroclastic mantle.

Reconstructing the Roman topography and environmental features of the Sarno River Plain (Italy) before the AD 79 eruption of Somma–Vesuvius

“…Due to this irregular cover of different strata which is characterized by a strong vertical variability of physical-mechanical properties, intense rainfall events can trigger slope instabilities, mass movements and thick submontane accumulations. These processes are still active today as the catastrophic landslide events of Sarno in 1998 have shown (Rao, 1995;Terribile et al, 2000;De Vita and Piscopo, 2002;Crosta and Dal Negro, 2003;Fiorillo and Wilson, 2004;Zanchetta et al, 2004;Terribile et al, 2007).…”

“…3). The Sarno River plain belongs to the great graben structure of the Campanian Plain which was formed during Plio-Pleistocene extensional tectonic phases at the end of the Apennine orogenesis and is filled with marine, alluvial and volcanic deposits lying on a carbonate platform (Cinque et al, 1987;De Vita and Piscopo, 2002;Cella et al, 2007).…”

Evaluation of the effect of land vegetation cover on water and energy balance of an unsaturated pyroclastic cover

“…Back analysis of the events occurred on Lattari Mts. (Gragnano and Pozzano, 1997; Nocera Inferiore, 2005) have pointed out the role of antecedent rainfall as predisposing conditions over a time periods also several months long [5,7,[11][12][13]. On these intervals, however, not only wetting events but also evaporative losses (low but persisting outward flows) have a significant influence in determining the predisposing conditions.…”

Research developments in debris flow monitoring, modelling and hazard assessment in Italian mountain catchments

“…Other numerical models were developed during the last two decades based on different assumptions [14][15][16][17][18][19]. Studies and researches on critical conditions of bed sediment entrainment due to debris flow, factors triggering debris flow, the determination of rheological characteristics of debris flow, configurations of debris-flow fan and run-out distances, based on flume tests, numerical and dimensional analysis, has also been carried out in Italy by many Authors [20][21][22][23][24][25][26].…”

“…Morphological characteristics of debris flows in Southern Italy were studied by different Authors [6], [22], [38], outlining the main causes. In all cases, besides the tectonic and lithological conditions which undoubtedly contributed to these processes, other anthropogenic causes, such deforestation and the processes of abandoning arable lands, thus causing alteration of local groundwater hydrology, play an important role in developing debris and mud flows [22].…”