Crossing the Grand Couloir (translated meaning: large gulley) makes up part of the technical scrambling section between the Tete Rousse and Gouter huts on the Gouter route it is shown by the horizontal section at one third height on the dotted red line on the photo below, the couloir being the broad parallel sided gulley the route traverses.This area is a well-known accident black spot in dry conditions (i.e. when there is little or no snow on the face binding the loose surface rocks together) stone fall can be channelled down the couloir to present a real danger to climbers crossing in between the relative safety of the sides.
There are quite simply times when rock fall makes the Gouter route unjustifiable. Each year is different: in 2013 and 2014 it did not happen at all, but between 2010 and 2012 there were perhaps two to three weeks a year affected on average, though not always at the same time of year. 2003 saw an unprecedented heat wave with the couloir impassable for half the season (fortunately Mont Blanc Guides started in 2004!), but to put that in perspective there were virtually no problems in the six years from 2004 to 2009.
Unfortunately 2015 turned out to be a mini rerun of 2003 with an intense heatwave hitting the alps in mid June. Summer temperatures in Chamonix (1000m) normally reach the high 20s and occasionally low 30s, but in 2015 there was a block of several days where the temperature passed 40°C, and the Grand Couloir was uncrossable for the best part of two months. This gave us our equal worst year since 2010 (when it didn't stop snowing!) with a success rate of only 35%, hopefully this will not become any more regular than once every 12 years... For more information on the 2015 heatwave and how we dealt with it, pleace click here. 2016, whilst not as good as we would hope, was largely a return to normality with about a ten day period at the beginning of September where the couloir became too dry.
Where an operator draws the line here varies a bit, but it is Mont Blanc Guides’ usual policy to be the first to renounce the ascent in marginal conditions and the last to resume it. Our safety record will always be much more important to us than our summiting record.
When conditions become too dry it is often possible to switch our attempts to the more difficult Cosmiques side but we cannot guarantee to be able to change hut bookings so this may not always be possible. Also the Cosmiques route demands a higher standard to make an ascent and is easily put out of condition by new snow/avalanche risk, which is why we pre-book the Tete Rousse hut on the Gouter route, where the chances of success are considerably higher.
This is unfortunately all part of climbing Mont Blanc, though it can be hard to take especially if, as is often the case, the couloir becomes too dry during a spell of good weather. All it takes however is a cool period with some new snow and it can quickly come back into condition. Unfortunately however many climbers try to force the issue and this leads to the often avoidable accidents that take place in the Grand Couloir every year. When the couloir is dangerously dry and the rocks are falling, the route is simply not there to be climbed.
The Route Between the Huts on Mont Blanc