Freeze–thaw cycles and rainfall as triggering factors of mass movements in a warm Mediterranean region: the case of the Tramuntana Range (Majorca, Spain)

Abstract

Freeze-thaw cycles and rainfall as triggering factors of mass movements in a warm Mediterranean region: the case of the Tramuntana Range (Majorca, Spain) Abstract Between 2008 and 2010, the island of Majorca (Spain) experienced the coldest and wettest winters of the last 40 years. Accumulated rainfall was twice the average and values of intense rainfall up to 296 mm/24h were recorded, very similar to those calculated for a return period of 100 years. Additionally, high precipitation coincided with anomalous, low temperatures, with abundant snowfall and freezing in the highest zones of the Tramuntana Range, in the northwest sector of the island. As a result, 34 mass movements were recorded on the range, which seriously affected the road network in an area of great importance for tourism, as it welcomes 8.5 million visitors each year. Fourteen rockfalls, 1 rock avalanche, 15 landslides and 4 karstic collapses were inventoried. The geological structure, formed by a series of NW overlapping thrusts, determines the distribution as well as the failure pattern of the movements. Thus, the northern face of the range registered 68% of the mass movements: nine rockfalls with planar failure took place as well as all the landslides recorded. Likewise, south-facing slopes have been affected by longer runout rockfalls with a wedge-type failure. The thorough analysis of the meteorological data shows that most of the movements have taken place after antecedent rainfall over 800mm. Additionally, the rockfalls have also occurred after several freeze-thaw cycles, being a determining and unusual factor in this warm region. Intense rainfall >90 mm/24h also caused rockfalls as well as exceptional very intense rainfall >120 mm/24h caused landslides. The results aim to contribute to the design of an early warning system coordinating emergency, infrastructure services and meteorological centres in a region of high risk.

Landslide Activity Maps Generation by Means of Persistent Scatterer Interferometry

“…(above sea level) everywhere, and the central sector (Lluc area) is the highest, with several peaks higher than 1,000 m, including Puig Major (1,445 m a.s.l. ), which is the highest peak on Majorca island [26]. The north coastal side of Tramuntana mountain range is the most abrupt and rugged, with prevalent very high cliffs overlooking the sea and steep slopes with 30-40% gradient percentage, while the southern side is smoother, characterized by a gentler gradient ( Figure 1c).…”

Exploitation of Large Archives of ERS and ENVISAT C-Band SAR Data to Characterize Ground Deformations

“…These rainy episodes also coincided with cold periods lasting several days with average temperatures approximately 0 °C and minima as low as −6.8 °C, which are anomalous values in the mild Mediterranean climate. One result was that 34 mass movements were triggered, distributed along the Tramuntana Range [46]. Fortunately, there were no deaths, but there were numerous cases of damage to dwellings, holiday apartment blocks, barns and power stations, and especially to the road network in the range; in particular, there were numerous blockages on the Ma-10 road, which caused significant economic losses in the various tourist resorts.…”

Influence of meteorological factors on rockfall occurrence in a middle mountain limestone cliff

“…Considering the rainfall amount, it amounts to 7.5 if the rainfall amount is between 30 and 40 mm. The influence of rainfall has been also shown by several authors (Chau et al, 2003;Mateos et al, 2012;Delonca et al, 2014). From a database with a daily precision, Delonca et al (2014) determined rockfall frequency for different rainfall conditions and for two transportation routes in Burgundy and La Réunion (France), with respectively limestone and volcanic rocks.…”

“…Several authors have described a correlation between rockfalls and freeze-thaw, using the occurrence of a freeze-thaw cycle (Douglas, 1980;Frayssines and Hantz, 2006;Mateos et al, 2012;Letortu et al, 2013) or the daily minimum tem- perature (Delonca et al, 2014). From the data of Frayssines and Hantz (2006) related to rockfalls in limestone cliffs of the French subalpine ranges with volumes between 10 and 10 5 m 3 , one can derive that the rockfall frequency is 2.4 times higher on days with freeze-thaw than on days without freeze-thaw (and 1.7 times the mean frequency).…”