Causes of Small Scale Landslides in Flysch Deposits of Istria, Croatia

摘要

In this paper we will present the overview of recent landslides in the Istria Peninsula, Croatia. The central area of the Istrian Peninsula is situated from the Trieste Bay in the west to the U?ka Mountain in the east and is called Gray Istria according to gray colour of the Paleogene flysch sediments. Flysch rocks mostly consist of claystones, siltstones with intercalated calcareous sandstones and breccia-conglomerates. During the last two decades many small scale landslides occurred in the area. Based on field investigations conducted during remedial works designing, a data base of investigated landslides was established. Landslides in flysch slopes of Gray Istria are mostly rotational slides, falls and debris flows of small scale. The sliding surface is typically on the contact of the superficial deposits and flysch bedrock which is almost impermeable below the superficial deposits with low permeability. Due to the inconvenient geological conditions, long term intensive rainfall and anthropogenic influence mostly during road construction, the natural balance in the slope was disturbed, and instabilities occurred.