Critical rainfall thresholds for triggering shallow landslides in the Serchio River Valley (Tuscany, Italy)

Abstract

Abstract. The Serchio River Valley, in north-western Tuscany, is a well-known tourism area between the Apuan Alps and the Apennines. This area is frequently hit by heavy rainfall, which often triggers shallow landslides, debris flows and debris torrents, sometimes causing damage and death. The assessment of the rainfall thresholds for the initiation of shallow landslides is very important in order to improve forecasting and to arrange efficient alarm systems.With the aim of defining the critical rainfall thresholds for the Middle Serchio River Valley, a detailed analysis of the main rainstorm events was carried out. The hourly rainfall recorded by three rain gauges in the 1935-2010 interval was analysed and compared with the occurrence of shallow landslides. The rainfall thresholds were defined in terms of mean intensity I , rainfall duration D, and normalized using the mean annual precipitation. Some attempts were also carried out to analyze the role of rainfall prior to the damaging events. Finally, the rainfall threshold curves obtained for the study area were compared with the local, regional and global curves proposed by various authors. The results of this analysis suggest that in the study area landslide activity initiation requires a higher amount of rainfall and greater intensity than elsewhere.

Analysing the relationship between rainfalls and landslides to define a mosaic of triggering thresholds for regional-scale warning systems

“…In particular, empirical rainfall thresholds are frequently used in operational warning systems (Brunsden, 1973;Aleotti, 2004;Hong et al, 2005;Tiranti and Rabuffetti, 2010;Cannon et al, 2011;Martelloni et al, 2012;. Among all rainfall thresholds approaches, the one using intensity-duration (I -D) thresholds (Caine, 1980) is perhaps the most popular: it has been proved particularly valid for shallow landslides (Caine, 1980;Crosta and Frattini, 2001;Ahmad, 2003;Jakob and Weatherly, 2003;Aleotti, 2004;Guzzetti et al, 2008;Giannecchini et al, 2012), and it has also been successfully applied to landslides in general (Zimmermann et al, 1997;Hong et al, 2005;Brunetti et al, 2010;Rosi et al, 2012).…”

“…The definition of the threshold from the I -D points has long been visually drawn with manual fitting (e.g. Caine, 1980;Giannecchini et al, 2012), and only recently has this issue been solved through proposing objective and robust statistical approaches to identify a threshold with a chosen confidence level from a given cloud of I -D points (Guzzetti et al, 2007(Guzzetti et al, , 2008Brunetti et al, 2010;Rosi et al, 2012).…”

Pre-2014 mudslides at Oso revealed by InSAR and multi-source DEM analysis

“…However, many landslides are repetitive, and therefore careful observation of critical factors, such as ground displacement, precipitation, stratigraphy, groundwater level, and stream flow, can reduce the risk of property damage and casualty loss (Anderson & Holcombe 2013). In particular, frequent observations over areas with high precipitation and deforestation can play a role in identifying the precautionary regions exposed to recurring landslides (Giannecchini et al 2012;George & Iverson 2014). Nevertheless, when a mountainous and steep region is our interest, acquiring the valuable spatio-temporal information can be challenging due to the lack of in situ data and disturbance by weather condition and rugged topography.…”

Rainfall Thresholds for Homeland Security in Mountainous Townships of Taiwan during Typhoon Morakot

“…In the study area of Chiayi County, this abnormally heavy rainfall led to 10 deaths with a further two missing, electricity outages for 11,300 buildings, hydraulic structures damaged in 30 places, roads damaged in 25 places, and 206 villages inundated by floods, landslides, and debris flows in over 700 locations, 22 bridges collapsed and 4 damaged, and estimated agricultural losses reaching NT$ 26 billion [9]. A rainfall threshold that combines the intensity, duration, and cumulative rainfall is commonly used for landslide and debris flow warnings [10]- [15]. At present this rainfall threshold warning model only addresses a single type of hazard (landslides, debris flows, or flood) and is less concerned about the hazards for relief workers and for potential disaster preparedness.…”