The November 2000 intense rainfall in the Pescia area (north Tuscany, Italy): characteristics and effects of the pluviometric event

Abstract

In Autumn 2000, the Province of Pistoia, and in general the north-western Tuscany and the nortern Italy, was hit by heavy and nearly uninterrupted rainfall, which reached the maximum intensity on November 20th. The rainstorm of November 20th caused many effects, in particular in the municipal district of Pescia, where numerous landslides, mostly of first generation, were triggered. The most frequent type of movement of the landslides was the sliding rapidly developed in flow. The main cause of the triggering of the landslides was attributed to a combination between a rainfall event, characterized by not particularly exceptional values of total rainfall and rainfall intensity, and a long period with abundant rainfall foregoing the event of November 20th. Considering the morphological and kinematical aspect, the landslides were typical of intense pluviometric events: rapid, shallow landslides (e.g. soil slip-debris flow) that involved almost exclusively the cover materials. They involved slopes characterized by rather typical geological and geomorphological environment for such phenomena (cover materials with small thickness, impermeable or semi- permeable bedrock, hollows, high gradient slope). Nevertheless, due to the long rainfall period, large and slow landslides were also activated.