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Blaise Agresti - The Gouter Problem on Mont Blanc

1. The document summarizes 3 studies conducted from 2010-2012 on accidents on the Gouter route of Mont Blanc: an accidentology study from 1990-2011, an analysis of rockfalls in summer 2011, and a feasibility study of safety measures. 2. The accidentology study found that the majority (47%) of accidents occurred in the couloir section, where falling rocks were the main risk. The risk of accidents increased on sunny days with many hikers. 3. The rockfall study observed 75% of rockfalls occurred from 10am-4pm, with the highest risk between 11am-12pm when over 1000 hikers crossed daily. Rockfall risk increased with sunny weather.

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1 The Gouter problem Normal route of Mont Blanc 3 studies to move forward 1 – Accidentology (summer-fall 2011) 2 –Danger and number of crossings (summer 2011) 3 – Technical solutions (2010-2011) july 2010 August 2011
Study n° 1 : Accidentology Rescues’ study on the Gouter route, between Tete Rousse refuge and Gouter refuge, from 1990 to 2011. Made with the help of PGHM, Rescue team from french mounted police. February 2012.
Goûter route Two kinds of accidents Objective danger, falling rocks during crossing the couloir Subjective danger, human related Glacier of Tête Rousse Old refuge Couloir New refuge Payot ridge Accidentologie-Goûter 3
Accidentologie-Goûter 4 Couloir ± 100 m Ridge ± 550 m Nid d’aigle to glacier of Tête Rousse ± 2 400 m Nid d’aigle to refuge du Goûter ± 3 400 m Ridge : 20 % of the route, 34 % of accidents Couloir : 3 % of the route, 47% of accidents 3270 m 3132 m 3817 m Alt. 2372 m Altitude Distance
Accidentologie-Goûter 5 Deaths 25% Injuries 62% unscathed 13% 74 deaths and 180 injuries between 1990 and 2011
0 2 4 6 8 10 12 14 16 long term consistency Décédées Blessées Indemnes Linear (Décédées) Linear (Blessées) Accidentologie-Goûter 6
0.000% 0.050% 0.100% 0.150% 0.200% 0.250% 0.300% Nbd'événementsparnuitéeauGoûter One death for 2400 nights in Goûter refuge Increase of injury rate over the last decade Décès Blessés Victimes Linear (Victimes) Accidentologie-Goûter 7
Accidentologie-Goûter 8 Couloir 3% of the route 38% of accidents Ridge 28% Payot ridge 3% Before Couloir 5% other 8% Unknow 18% Localisation of the accidents 1990 to 2011 Couloir 47% Ridge 34% Payot 4% Beforel Couloir 6% Other 9% After proportional repartition
France 30% Espagne 13% RU 8% Pologne 7% Allemagne 6%Italie 5% Belgique 5% Tchéquie 3% Croatie 2% Pays-Bas 2% Slovaquie 2% Danemark 2% Autriche 1% Finlande 1% Hongrie 1% Slovénie 1% Suisse 1% Grèce 1% Lituanie 1% Serbie 1% Suède 1% Japon 2% Corée 2% Canada 1% EUA 1% Israël 1% Argentine 1% Injuries from 27 countries Accidentologie-Goûter 9
France 15% Allemagne 12% Espagne 11% Tchéquie 11% Pologne 9% Italie 8% Lituanie 5% Belgique 4% RU 4% Autriche 3% Hongrie 3% Pays-Bas 3% Ukraine 3% Danemark 1% Irlande 1% Macédoine 1%Slovénie 1% Suisse 1% Slovaquie 1% Japon 1% Deaths from 20 countries Accidentologie-Goûter 10
Accidentologie-Goûter 11 Study n°2 : Analysis of falling rocks and numbers of ascents during summer 2011
Accidentologie-Goûter 12 Study made by engineers in geotechnics Observation : from 20th june to 18th september 2011 Observations made by Heïdi SEVESTRE, alpinist and doctorate in glaciology • 11 sessions from 2 to 4 days in duration • 42 days total of observation METHODOLOGY
Accidentologie-Goûter 13 Observations : Weather forecast datas :  Temperature  Humidity  Speed and direction of the wind  Rain  Solar radiation
Zone 1 2 3 4 5 6 7 % 30 % 21 % 12 % 21 % 6 % 1 % 9 % Falling rocks analysis Departure zone : Third of the rocks fall from the summit
02/07/11 08/07/11 19/07/11 21/07/1120/07/11 Significant reduction in falling rocks with temperature below O°C
Significant increase falling rocks with sunny weather Air humidity : 30/06/11 01/07/11 28/07/11 12/08/11 29/07/11 11/08/11
CONCLUSIONS Event : 75 % falling rocks between 10 am and 4 pm. Most critical period : one event of rock fall every 17 minutes between 11 am and 12 am No change with or without snow. Frequency : 17 000 to 17 500 passages during summertime. One person every 105 second between 12 am and 1pm Almost 1000 persons are subjected to rock fall during the season. Most dangerous period : during sunny weather combine with the middle of the day => during the most important crossings. .
Accidentologie-Goûter 18 Study n°3 : Feasibility study and preliminary draft of security measures proposed
Accidentologie-Goûter 19
Accidentologie-Goûter 20
Accidentologie-Goûter 21 Rejected solutions of security > Limitation of crossings : illusory > information, cable : Necessary but not sufficient. > Purgings and anchorings: difficult, dangerous, unsuited. > Protection by nets: landscape impact, heavy and dangerous maintenance. > Protection by reinforced concrete work: problem of solidity and integration in the environment. > Himalayan bridge: First idea, but blocks bouncing too high (35 m), fast risk of destruction, to 25 m, too heavy landscape impact with 35m
Accidentologie-Goûter 22 One solution to think about : a small tunnel
Accidentologie-Goûter 23 Estimate cost : 821 K€ TTC for a 107 m tunnel 1 084 K€ TTC for a 168 m tunnel
Accidentologie-Goûter 24 Foundation goals To bring objective elements to nourish the reflexions. To awake. To defend the beautiful risk, not the Russian roulette. To promote the reduction of the objective risk, without denaturing the mountain. To reflect on the basis of concrete solution, not only of the intentions.