Dry Spells and Extreme Precipitation are The Main Trigger of Landslides in Central Europe

Radek Tichavský,Karel Šilhán,Juan Antonio Ballesteros-Cánovas,Radim Tolasz,Markus Stoffel

doi:10.1038/s41598-019-51148-2

Radek Tichavský, Karel Šilhán + Show 3 more

Open Access

https://doi.org/10.1038/s41598-019-51148-2

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Abstract

Landslides are frequently triggered by extreme meteorological events which has led to concern and debate about their activity in a future greenhouse climate. It is also hypothesized that dry spells preceding triggering rainfall may increase slope predisposition to sliding, especially in the case of clay-rich soils. Here we combined dendrogeomorphic time series of landslides and climatic records to test the possible role of dry spells and extreme downpours on process activity in the Outer Western Carpathians (Central Europe). To this end, we tested time series of past frequencies and return periods of landslide reactivations at the regional scale with a Generalized Linear Mixed (GLM) model to explore linkages between landslide occurrences and triggering climate variables. Results show that landslide reactivations are concentrated during years in which spring and summer precipitation sums were significantly higher than usual, and that triggering mechanisms vary between different types of landslides (i.e. complex, shallow or flow-like). The GLM model also points to the susceptibility of landslide bodies to the combined occurrence of long, dry spells followed by large precipitation. Such situations are likely to increase in frequency in the future as climate models predict an enhancement of heatwaves and dry spells in future summers, that would be interrupted by less frequent, yet more intense storms, especially also in mountain regions.

Highlights

Landslides represent global natural hazards causing thousands of fatalities every year and heavy devastation of infrastructure[1]
Years with landslide reactivations show significantly higher annual precipitation sums than those without landslide activity (p = 0.02), and even more so when summer (p = 0.01) or spring (p = 0.04) precipitation sums are taken into consideration
We demonstrate that mass movements are triggered by precipitation, but that dry spells have a significant influence on landsliding as well in the Outer Western Carpathians

Summary

Introduction

Landslides represent global natural hazards causing thousands of fatalities every year and heavy devastation of infrastructure[1]. The combined effect of dry spells and extreme rainfall has been linked to landslide activity due to shrinking-swelling effects of clayey minerals in the weathered bedrock of landslide bodies[10,26]. In this context, the current understanding is that macropores of clay-rich soils would www.nature.com/scientificreports/. The combined occurrence of both phenomena – dry spell duration and precipitation intensity – is referred to as hydroclimatic intensity and shown to have increased in response to global warming over the second half of the 20th century[28]. The actual triggering of landslides depends on the structural setting and lithology which in turn may differ among different landslide types: deep-seated landslides are generally thought to respond to excessive monthly and/or seasonal rainfall sums, whereas shallow landsliding would depend mainly on intense, yet short-lived rainfall peaks[5,29]

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