Slope movements and unusual precipitation periods in High Omaña Valley (Cantabrian Mountains, Northwest León)

Abstract

We analyze 150 slope movements that occurred in the Omaña river basin (Cantabrian Mountains, León province, Spain). All of these movements triggered during the exceptionally rainy winter 2000-01 (about 2.000 mm between October 2000 and March 2001, when normal rainfall in these months is about 500 mm). All of them occurred in slopes of old glacially valleys, with till and periglacial regoliths in surface. These slopes were cultivated for centuries and abandoned since 1960. The changes in the land use, the combination of different regoliths, and the high gradients, encourage the slope instability in this area. Exceptional rainfalls were the starting factor of the landslides. Almost all of the landslides were small, in some cases affecting roads, towns and other human goods, being cause of dangerous situations.