Suchergebnisse

Abstract. This paper presents an extended reanalysis of the rainfall-induced geo-hydrological events that have occurred in the last 70 years in the alpine area of the Lombardy region, Italy. The work is focused on the description of the major meteorological triggering factors that have caused diffuse episodes of shallow landslides and debris flow. The aim of this reanalysis was to try to evaluate their magnitude quantitatively. The triggering factors were studied following two approaches. The first one
started from the conventional analysis of the rainfall intensity (I) and
duration (D) considering local rain gauge data and applying the I–D
threshold methodology integrated with an estimation of the events' return
period. We then extended this analysis and proposed a new index for the
magnitude assessment (magnitude index, MI) based on frequency–magnitude theory. The MI was defined considering both the return period and the spatial extent of each rainfall episode. The second approach is based on a regional-scale analysis of meteorological
triggers. In particular, the strength of the extratropical cyclone (EC) structure associated with the precipitation events was assessed through the sea level pressure tendency (SLPT) meteorological index. The latter has been estimated from the Norwegian cyclone model (NCM) theory. Both indexes have shown an agreement in ranking the event's magnitude
(R2=0.88), giving a similar interpretation of the severity that
was also found to be in accordance with the information reported in historical
databases. This back analysis of 70 years in Valtellina identifies the MI and the SLPT
as good magnitude indicators of the event, confirming that a strong cause–effect relationship exists among the EC intensity and the local
rainfall recorded on the ground. In respect of the conventional I–D
threshold methodology, which is limited to a binary estimate of the likelihood of landslide occurrence, the evaluation of the MI and the SLPT
indexes allows quantifying the magnitude of a rainfall episode capable of
generating severe geo-hydrological hazards.

La sociologie de l'environnement est un domaine disciplinaire récent en Italie. La naissance de cet objet d'étude montre la nécessité de proposer une lecture de la société et de la «qualité de vie» par des démarches nouvelles. Elle prend donc l'aspect d'une nouvelle vision du monde plus que d'un domaine spécifique d'étude, en se déclinant en une série de connaissances empiriques et de choix stratégiques liés à des problématiques et des champs différents. L'article dresse un historique de la sociologie de l'environnement en Italie, en précisant le contenu du champ qu'elle délimite.

Abstract. This work presents the new model called CRHyME (Climatic Rainfall Hydrogeological Modelling Experiment), a tool for geo-hydrological hazard evaluation. CRHyME is a physically based and spatially distributed model written in the Python language that represents an extension of the classic hydrological models working at the basin scale. CRHyME's main focus consists of simulating rainfall-induced geo-hydrological instabilities such as shallow landslides, debris flows, catchment erosion and sediment transport into a river. These phenomena are conventionally decoupled from a hydrological routine, while in CRHyME they are simultaneously and quantitatively evaluated within the same code through a multi-hazard approach. CRHyME is applied within some case studies across northern Italy. Among these, the Caldone catchment, a well-monitored basin of 27 km2 located near the city of Lecco (Lombardy), was considered for the calibration of solid-transport routine testing, as well as the spatial-scale dependence related to digital terrain resolution. CRHyME was applied across larger basins of the Valtellina (Alps) and Emilia (Apennines) areas (∼2600 km2) which have experienced severe geo-hydrological episodes triggered by heavy precipitation in the recent past. CRHyME's validation has been assessed through NSE (Nash–Sutcliffe efficiency) and RMSE (root mean square error) hydrological-error metrics, while for landslides the ROC (receiver operating characteristic) methodology was applied. CRHyME has been able to reconstruct the river discharge at the reference hydrometric stations located at the outlets of the basins to estimate the sediment yield at some hydropower reservoirs chosen as a reference and to individuate the location and the triggering conditions of shallow landslides and debris flows. The good performance of CRHyME was reached, assuring the stability of the code and a rather fast computation and maintaining the numerical conservativity of water and sediment balances. CRHyME has shown itself to be a suitable tool for the quantification of the geo-hydrological process and thus useful for civil-protection multi-hazard assessment.