Relationships between viticulture practices and hydrogeological hazards: Case studies in the «Terre del Barolo» area (Langhe Hills, Piemonte, Italy) [Relazioni fra attività vitivinicola e dissesto idrogeologico: Esempi di studio dalle Terre del Barolo]

Modern Earth Sciences contributions to terroir studies have not to be limited to systematic comparative analysis of relationships between products and pedological, lithological, structural and stratigraphical conditions: they have to be extended to other scientific researches, relating to natural hazards capable to endanger the very existence of terroir in a specific area. Therefore, a complex of applied geological and geomorphological studies have been performed in the «Terre del Barolo» (or «Barolo Lands»), a territory located at the north-western side of the Langhe Hills, Southern Piemonte Region, Italy; this is the worldwide famous area for the production of the Barolo wine. From a geological point of view, the area is characterized by the late- and post-orogenic sedimentary rocks of the Tertiary Piemonte Basin: it is a terrigenous sequence of Oligocene-Upper Miocene age with a gentle monoclinal uplifting structure, responsible for the «cuestas» morphogenesis carried out by fluvial erosion. In the «Terre del Barolo», the prevailing lithological units are marls and sand-stones of Langhian, Serravallian and Tortonian formations. The hillslopes of the studied area are affected by widespread landslides of various type, the rock-block (planar) slides showing the largest extent and being the most destructive phenomena. Soil-slips and mud flows have a minor impact as single cases in the ordinary pluviometric regime, being more extensive and extremely hazardous during extraordinary meteorological events, such as the regional November 4 th-6th 1994 heavy meteorological event (567 mm of maximum cumulated rainfall; 3500 km2 of major damages area in the whole Piemonte Region). This paper highlights the relationships and interdependences between grape growing and geomorphological processes; particularly, the compatibility of certain viticulture practices over unstable slopes is investigated. Historical data collection, aerial photointerpretations and detailed field surveys of geological, geomorphological and hydrological features have been carried out at a general (1:10000) and local scale (1:2500) in order to identify unstable areas and determine characteristics of landslides and effective or possible damages to human structures and products. In addition, a series of safety regulations and recommended practices is proposed, as a prospect for a functional land use, respectful to the sensitive and fragile hydrogeological equilibrium of the hillslopes. Specific interventions dedicated to different instability phenomena are singled out, in addition to recommended or avoidable viticulture practices. Finally, a research methodology is suggested, applicable to the studies of other high-vulnerability wine producing areas, in order to get a better landscape and terroir characterization, a precise active geomorphological processes identification, a functional natural hazard evaluation.