Abstract
Abstract. On the 27 and 28 April 2009, the area of Oltrepo Pavese in northern Italy was affected by a very intense rainfall event that caused a great number of shallow landslides. These instabilities occurred on slopes covered by vineyards or recently formed woodlands and caused damage to many roads and one human loss. Based on aerial photographs taken immediately after the event and field surveys, more than 1600 landslides were detected. After acquiring topographical data, geotechnical properties of the soils and land use, susceptibility analysis on a territorial scale was carried out. In particular, different physically based models were applied to two contiguous sites with the same geological context but different typologies and sizes of shallow landslides. This paper presents the comparison between the ex-post results obtained from the different approaches. On the basis of the observed landslide localizations, the accuracy of the different models was evaluated, and the significant results are highlighted.
Highlights
Vegetation, land use and their change in time are widely recognized as important factors influencing rainfall-triggered landslides (Begueria, 2006a); the models were applied to two contiguous sites with the same geological context, but different land cover change, which results in different typologies and sizes of shallow landslides
Two different data sets of shallow landslides were used as input data for the physically based models: the first data set considers all typologies of landslides, and the second excludes the slides that occur on the slopes adjacent to the roads, which are considered to be due to anthropologically induced instabilities (Fig. 9)
The methods were applied to two contiguous sites with the same geological context but with different land cover, which results in different typologies and sizes of shallow landslides
Summary
The study area is located in the northeastern sector of Oltrepo Pavese, where many shallow-seated landslides occurred due to rainfall on 27–28 April 2009 and which belongs to the northwestern Italian Apennines (Fig. 1). April 2009 rainfall event (∼ 24 landslides per square kilometer, equal to approximately 0.5 % of the entire area). On the 28 April, the Cigognola rain-gauge station recorded 150 mm of rain in 48 h (20 % of the annual average amount), with a maximum rainfall intensity of 22 mm h−1 at 9 p.m. on 27 April (Fig. 2) After this peak was reached, several shallow landslides were triggered, causing one fatality and loss of agricultural land, as well as damaging/blocking roads in several places.
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