Avalanches and Landslides – France

Avalanches, Landslides and Rock fall France

Vulnerabilities- Avalanches

With attentiveness to avalanches and landslides, the impacts of climate change remain uncertain ( 1 ) .
A change in avalanche hazards in connection with climate switch is uncertain. In general, it is assumed that the possible change would follow the coke cover evolution. A decrease in avalanche hazards is probably at low and medium altitudes. Yet, heavy haste events might counterbalance this drift by triggering general avalanche situations ( 2 ) .

Vulnerabilities – Alpine mass movements

The abasement of permafrost in steep slopes is a major factor for the reduce stability of rock walls and the rock fall convention. Increased precipitation might lead to more patronize and extended gradient instabilities in the future. In particular, the changes of intense precipitation could impact the shallow landslides ( through the open water overflow and stream actions ), while the changes of long-run precipitation could impact the deep landslides ( through underground water natural process ). On the other hand, the possible future decrease of summer haste may have a incontrovertible effect by reducing the deep and shallow landslides natural process ( 2 ) .
The zone of warm permafrost ( base annual rock temperature approximately -2 to 0°C ), which is more susceptible to slope failures than cold permafrost, may rise in elevation a few hundred meters during the following 100 years ( 3 ). This in twist may shift the zone of enhanced instability and landslide initiation toward higher-elevation slopes that in many regions are exorbitant, and therefore predisposed to failure.

The projected glacier retreat in the twenty-first century may form new potentially unstable lakes. probable sites of modern lakes have been identified for some alpine glaciers ( 4 ). Rock gradient and moraine failures may trigger damaging surge waves and outburst floods from these lakes .

Vulnerabilities – Landslides

The Alps

Projections of climate change between 2010 and 2100 have been translated into future debris stream activeness for two Alpine catchments, one in France ( Barcelonnette Basin ) and one in Italy ( Fella River catchment ) ( 11 ). These projections are based on a number of regional climate models ( driven by general circulation models ) and both an intercede and high-end scenario of climate change ( the alleged RCP4.5 and RCP8.5 scenarios, respectively ). From the model outcomes two meteorologic proxies for debris flow natural process were derived and translated into future debris flow natural process : one using 1-day rain amounts and one being congressman of short-lasting convective rain systems. The 1-day rain-proxy was chosen as precipitation is a dominant trip of debris flows. As rain gauges are very local and often non-catchment example, the moment proxy was used to mimic the mesoscale atmospheric conditions leading to heavy local convective precipitation. All of these projections show either an increase or little variety in the number of days with debris flows between now and 2100 ( 11 ) .
An inventory of 2966 landslides in the french and swiss assign of the European Alps over the period 1970–2002 ( 10 ) shows that the majority of landslides recorded occurred during the spring ( March/April/May, 29 % ) and summer ( June/July/August, 36 % ), with the lowest numbers recorded during fall ( September/October/November, 15 % ) and winter ( December/January/February, 20 % ) .
It is hard to predict changes in landslide occurrence from projected changes in precipitation due to climate change since changes in precipitation patterns are hard to predict at the small-scale. As an option approach, changes in weather types can be used as a predictive tool for landslide events under differing future climate scenarios. One should be aware, however, that other factors ( such as rain continuity, geology and topography ) play an crucial function in the happening of landslides as well ( 10 ) .
For the Alps, the main trigger of debris flows is high volume, short duration rain ( 12 ). Under future climate change, it is likely that increases in extreme rain will alter debris flow frequency ( 13 ). previously, a limited number of climate change impact studies focused on debris flows, with inconsistent results : some indicating less debris flows in the future ( 14 ), others more ( 15 ), or concluding that accurate quantification of changes in the number of debris flows is not potential ( 16 ) .

The Pyrenees

The risk of landslides in mountainous areas may change in the future specially as a result of climate transfer and changes in state cover. The link with climate switch is the effect of changes in moisture contented in the subsoil due to changes in precipitation intensity and book, and a shift from snow to rain. Changes in land cover can affect slope stability through different processes : on the one hand, the roots of plants and trees increase slope stability ; on the other, vegetation adds system of weights to the slope and more weight increases the risk of a landslide. Vegetation besides influences moisture content of the subsoil ( 24 ) .
To make things more complicated, there are several types of landslide. The sensitivity of landslides to changes in climate or land cover may depend on particularly the size and astuteness of the landslide ( 25 ). Shallow landslides are generally governed by shorter-duration rain, and consequently by changes in the volume of rain. In contrast, deep-rooted landslides may be affected by changes on a much longer term, such as changes in the monthly rain, seasonal coke or groundwater .
How important is climate switch when compared to changes in farming report for future changes in the risk of landslides ? This was studied for a high-elevation valley in the french Central Pyrenees. future projections were assessed for four different scenarios of farming consumption, leading to more or less forest cover, and for two scenarios of climate exchange, a moderate ( the RCP4.5 scenario ) and high-end scenario ( RCP8.5 ). These projections refer to the near future ( 2021-2050 period ) and far future ( 2071-2100 period ). The results were compared with the situation of 1981-2010 for mention ( 24 ).

The results show that for this font climate transfer has a stronger impact on landslide risk than changes in land cover. Climate change may sporadically increase the water postpone in the subsoil such that slope stability decreases. This effect even dominates over the gradient stabilizing consequence of more forest cover. This is particularly significant for the high-end scenario of climate change. refore, evening if future forest growth leads to slope stabilization, the evolution of the groundwater conditions will lead to destabilization ( 24 ) .
According to this study, landslide hazards in this character of the Pyrenees are projected to occur 1.5 and 4 times a much in the approximate and far future, respectively, under the high-end scenario of climate change. The addition of landslide frequency in areas prone to landslides is higher for the shallow landslide type than for the deep landslide character ( 24 ) .

IPCC conclusions in 2012

In 2012 the IPCC concluded that there is high confidence that changes in heat waves, frigid retreat, and/or permafrost abasement will affect eminent mountain phenomena such as slope instabilities, mass movements, and glacial lake outburst floods, and medium confidence that temperature-related changes will influence fundamentals constancy. There is besides eminent assurance that changes in heavy precipitation will affect landslides in some regions ( 5 ). There has been an apparent increase in large rock slides during the past two decades, and specially during the first gear years of the twenty-first hundred in the European Alps ( 6 ) in combination with temperature increases, glacier shoplifting, and permafrost degradation .
There is medium confidence that high-mountain debris flows will begin earlier in the year because of earlier snowmelt, and that continued batch permafrost degradation and glacier retreat will further decrease the stability of rock slopes. There is depleted confidence regarding future locations and timing of large rock avalanches, as these depend on local geological conditions and early non-climatic factors ( 5 ). Research has not even provided any clear indication of a change in the frequency of debris flows due to recent deglaciation. In the french Alps, for exemplify, no significant change in debris flow frequency has been observed since the 1950s in terrain above elevations of 2,200 thousand ( 7 ). Processes not, or not immediately, driven by climate, such as sediment yield, can besides be authoritative for changes in the order of magnitude or frequency of alpine debris flows ( 8 ) .

IPCC conclusions in 2019

Rock fall

The IPCC concluded in 2019 that there is high confidence that the frequency of rocks detaching and falling from steep slopes ( rock fall ) has increased within zones of degrading permafrost over the past half-century, for exemplify in high mountains in Europe ( 17 ). available field testify agrees with theoretical considerations and calculations that permafrost thaw increases the likelihood of rock fall ( and besides rock avalanches, which have larger volumes compared to rock falls ) ( 18 ). Summer heat waves have in holocene years triggered rock ‘n’ roll instability with delays of only a few days or weeks in the European Alps ( 19 ) .

Snow avalanches

In the European Alps, avalanche numbers and runout outdistance have decreased with decreasing snow depth and increasing tune temperature ( 20 ). In the European Alps and Tatras mountains, over past decades, there has been a decrease in avalanche mass and run-out distance, a decrease of avalanches with a powder part since the 1980s, a decrease of avalanche numbers below 2000 thousand, and an increase above ( 21 ) .
future projections largely indicate an overall decrease in snow depth and snow cover duration at lower elevation, but the probability of occurrence of occasionally big snow precipitation events is projected to remain possible throughout most of the twenty-first hundred ( 17 ). An overall 20 and 30 % decrease of natural avalanche activity in the french Alps is estimated for the mid and goal of the twenty-first century, respectively, under a mince ( A1B ) scenario of climate change, compared to the citation time period 1960 – 1990 ( 22 ). The overall number and runout distance of snow avalanches is projected to decrease in regions and elevations experiencing significant decrease in bamboozle cover ( 23 )
Avalanches involving wet snow are projected to occur more frequently during the winter at all elevations ascribable to surface mellow or rain-on-snow ( 22, for the French Alps ).

In drumhead, there is metier testify andhigh agreement that observed changes in avalanches in batch regions will be exacerbated in the future, with generally a decrease in hazard at lower elevation, and mix changes at higher elevation ( increase in avalanches involving wet bamboozle, no clear guidance of swerve for overall avalanche action ) ( 17 ) .

Adaptation strategies – AdaptAlp

According to AdaptAlp, a project of the six Alpine countries on natural hazards in the Alpine region, the ten-spot most significant actions required at this time to prepare for the risks caused by ball-shaped heating in the Alps are ( 9 ) :

• Improve public preparedness and personal responsibility by encouraging participation in emergency planning. To properly inform the public, risk management plans must address both emergency preparedness and early warning systems.
• Incorporate climate change adaptation into spatial planning. A few examples to create a sustainable regional development that is less vulnerable to natural hazards are: financial incentives, establishing hazard zones, setting appropriate construction standards of buildings and infrastructure in risk areas, keeping endangered spaces free of development, and performing hazard assessments through the use of hazard mapping.
• Involve local stakeholders in a risk dialogue. The dialogue includes meetings between important stakeholders, such as land and real estate owners, as well as those responsible for infrastructure and the public sector.
• Encourage cross-border networking on integrated risk management.
• Encourage a ‘common language’ and harmonised procedures when developing and using hazard maps.
• Increase the size of flood plains, floodwater conduits and basins. Governments need to consider multiple uses of the same land and consider strict legal binding instruments that ensure a priority for flood retention areas is given.
• Think of flood risk management in terms of an entire river basin to find solutions that are sustainable. Horizontal and vertical cooperation between all levels of government and the private sector are essential.
• When planning for natural hazard risks consider all the environmental risks within a defined area. Natural hazards—floods, droughts, landslides—generate risks that are interrelated and so should be addressed jointly.
• Use risk-management tools to explore the social and economic consequences of various adaptation measures. Risk planning tools allow for the integration of a wide range of strategies that reduce the risks of natural hazards, including spatial planning instruments, technical protection structures, specific protection measures for individual buildings and early-warning systems.
• Support the collection and interpretation of local climate change data.

References

The references below are cited in full in a branch map ‘References ‘. Please click here if you are looking for the full moon references for France .

1. ONERC (2007/2009)
2. ESFR ClimChAlp (2008b), in: Castellari (2009)
3. Noetzli and Gruber (2009), in: IPCC (2012)
4. Frey et al. (2010), in: IPCC (2012)
5. IPCC (2012)
6. Ravanel and Deline (2011), in: IPCC (2012)
7. Jomelli et al. (2004), in: IPCC (2012)
8. Lugon and Stoffel (2010), in: IPCC (2012)
9. AdaptAlp
10. Wood et al. (2016)
11. Turkington et al. (2016)
12. Schneuwly-Bollschweiler and Stoffel (2012); Stoffel et al. (2014); Van den Heuvel et al. (2016), all in: Turkington et al. (2016)
13. Winter et al. (2010), in: Turkington et al. (2016)
14. Jomelli et al. (2009), in: Turkington et al. (2016)
15. Stoffel et al. (2014), in: Turkington et al. (2016)
16. Melchiorre and Frattini (2012), in: Turkington et al. (2016)
17. IPCC (2019)
18. Gruber and Haeberli (2007); Krautblatter et al. (2013), both in: IPCC (2019)
19. Allen and Huggel (2013); Ravanel et al. (2017), both in: IPCC (2019)
20. Teich et al. (2012); Eckert et al. (2013), both in: IPCC (2019)
21. Eckert et al. (2013); Lavigne et al. (2015); Gadek et al. (2017), all in: IPCC (2019)
22. Castebrunet et al. (2014), in: IPCC (2019)
23. Mock et al. (2017), in: IPCC (2019)
24. Bernardie et al. (2021)
25. Crozier (2010), in: Bernardie et al. (2021)