Hystorical and recent hydrogeological instability in the Monte Modino area: Valoria, Tolara and Lezza Nuova landslide reactivations (Dolo – Dragone valleys, Modena Apennines, Italy)

Following the heavy rainfalls of autumn 2000 a strong resumption of hydrogeologicalinstability was observed throughout the whole Emilian Apennines. In the Modena provincethe effect of such event was the reactivation of many landslides. In the Monte Modino area(an elongated mountain ridge bounded by Dolo and Dragone stream valleys, high ModenaApennines) three large complex landslides (Valoria, Tolara and Lezza Nuova) werereactivated. While landslides were triggered by a strong increase in precipitation, the maincause of slope instability is possibly related to the peculiar hydrogeological setting of thewatershed: a thick unit of highly fracturated sandstones overlying a clayey formation. Inthis paper, the role of abundant rainfall events, periodically occurring in the ModenaApennines, as primary cause for landslide reactivation is discussed.The preliminary stabilisation works adopted by the “Servizio Tecnico Bacini Panaro edestra Secchia Modena”, have been restricted to restoration of slope stability withrehabilitation of the drainage system within each single landslide, mainly duringemergencies.We believe that, due to the peculiar hydrogeological setting of Monte Modino area, futureinterventions should provide the stabilization of the whole watershed area. An overalldrainage of Monte Modino sandstone unit is proposed to achieve this target.