Rockfall and Rainfall Correlation in the Anaga Nature Reserve in Tenerife (Canary Islands, Spain)

Sergio Leyva,Jesica Rodríguez-Martín,Luka Miklin,Noelia Cruz-Pérez,Juan C. Santamarta

doi:10.1007/s00603-021-02762-y

Abstract

AbstractRockfalls are frequent and damaging phenomena that occur on steep or vertical slopes, in coastal areas, mountains and along coastal cliff. Water, in different forms, is the most common triggered factor of rockfalls. Consequently, we can consider that precipitation is the most influential factor for slope instabilities and it influences almost all other water parameters. Besides, the specific geology of the Anaga nature reserve in the volcanic island of Tenerife, together with its steep landscape, contributes to the instability of the slopes and frequent rockfalls. Recently, due to climate change and global warming, the annual precipitation/rainfall has declined but the number of heavy storms, associated with intense rainfall and strong winds, events that exceed precipitation thresholds in a brief period has increased which triggers slope movements. This paper describes the analysis of information on rainfall-induced rockfalls in Anaga, Tenerife (Canary Islands), to forecast rock failures of social significance and to improve the capability to respond and emergency decision making. To define reliable thresholds for a certain area, we analized information during the period 2010–2016, reconstructed the rockfall events, and statistically analyzed the historical rainfall conditions that led to landslides. The summary graph correlating precipitation to the probability of occurrence of an event was plotted. Statistical and probability graphs were made with the direct relationship between the number of rockfall events and total rainfall in that period by examining the maximum daily precipitation, not only on the day of the event but up to 3 days before. Hence, the results of this study would serve as a guide for the possible forecasting of rainfall-induced rockfalls, especially for road maintenance services, so that they can be on alert or mobilize the necessary resources in advance depending on the intensity of the expected rainfall.

Highlights

Rockfalls are, by definition, a type of landslide involving abrupt downward movement of rock or soil, or both, that detach from steep slopes or cliffs (Highland and Bobrowsky 2008)
The volume of material in a rockfall can vary considerably, from individual rocks or clumps of soil to massive blocks thousands of cubic meters in size (Margottini et al 2013). Whether it is solid water, whether it is in liquid form such as rain, groundwater, melting ice, etc.; or whether it is water pressure, water energy, seismic activity, or anthropogenic activities, etc., is the most common cause of rockfalls (Ansari et al 2015; de Vallejo et al 2020a, b; Hibert et al 2011; Hürlimann et al 1999; Keefer 2002; Mateos et al 2020; Saroglou 2019; Uchimura et al 2010; Wieczorek and Jäger 1996)
The methodology followed for data collection was: 1. Collec data on all events classified as “Rockfalls” that occurred during the period 2010–2016 that were addressed by the personnel assigned to the Contracts of Integral Conservation of Roads (North, South, West and Anaga Sectors), promoted by the Cabildo Insular de Tenerife and conducted by external companies

Summary

Introduction

By definition, a type of landslide involving abrupt downward movement of rock or soil, or both, that detach from steep slopes or cliffs (Highland and Bobrowsky 2008). The volume of material in a rockfall can vary considerably, from individual rocks or clumps of soil to massive blocks thousands of cubic meters in size (Margottini et al 2013) Water, whether it is solid water (ice, snow), whether it is in liquid form such as rain, groundwater, melting ice, etc.; or whether it is water pressure, water energy (undercutting of slopes by natural processes such as streams, rivers, and ocean/sea waves), seismic activity, or anthropogenic activities (burst water pipes, and similar), etc., is the most common cause of rockfalls (Ansari et al 2015; de Vallejo et al 2020a, b; Hibert et al 2011; Hürlimann et al 1999; Keefer 2002; Mateos et al 2020; Saroglou 2019; Uchimura et al 2010; Wieczorek and Jäger 1996). These precipitation thresholds include numerous uncertainties that limit their application in early warning systems (Rosi et al 2020; Melillo et al 2018; Guzzetti et al 2020)

Methods

Results

Conclusion