Date: Wed, 21 Aug 1996 13:04:09 -0700 From: Phil Hammer Cc: hammer@geop.ubc.ca Subject: Avalanche Incident Report The avalanche reports you have for "Canada - May 19, 1996" are brief and/or slightly inaccurate. In fact, many (all?) of the media reports regarding this accident contained erroneous information regarding snowpack, weather conditions, slope aspect etc. The avalanche actually occurred on May 17, 1996. vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv DETAILS OF THE ACCIDENT ON CERBERUS MOUNTAIN (May 17, 1996) GENERAL WEATHER/SNOWPACK: The Coast Range was subject to a very cool April and May. As a result, the snowpack at elevations above 8,000' still exhibited Coastal late-winter characteristics (rather than the often bomb-proof late-spring pack). Weather on the Monarch Icefield the 2 weeks preceding the accident had been predominantly cool (-10C to 2C), cloudy, and windy. Small amounts of snow were deposited, but wind loading was a more important issue when judging slope stability. Very few natural avalanches were observed over those 2 weeks. Those that occurred were on very steep slopes of various aspects. LOCATIONS: The party of five were two weeks into their three week, unsupported traverse of the Monarch Icefield, a large glacier system in the western Coast Range (north of Mt. Waddington, near Bella Coola, BC). Four of the group were very experienced mountaineers/skiers that were well known and respected in Vancouver mountaineering circles. They annually participated in 3-5 week exploratory ski-mountaineering traverses in Coastal BC, Yukon and Alaska. The group left camp intending to climb Mt. Cerberus (10,300') by the NW face - the only non-technical route up the mountain. This narrow, 30-45 degree glacier rises from a basin at 9,000' to the summit ridge at 10,000'. Looking up the slope, an icefall spills off to the right and vertical cliffs extend further right. WEATHER: Cold (-10C to -2C), heavy overcast with lenticulars, windy. ASPECT: NW - not exposed to sun until after 12:00 ACCIDENT: Four of the party skied approximately 1/4 of the way up the slope. There they performed two shovel tests and a rutschblock test. Results from all three snow stability tests were consistent. There was a 30 cm layer of storm snow, accumulated over the past week, that had a shear layer in the middle. It took moderate-strong force to make it slide. The rutschblock yielded a similar result (RB 4-5). The base of the storm snow was well bonded to the deeper, consolidated snow. One meter down there was a double ice layer that they could not make release. The group was concerned about the shallow shear layer, and after some discussion decided it would be safest to continue by foot rather than ski. The group also decided to check the snowpack again later since the wind effects appeared to be more significant higher on the slope. About halfway up the slope, they stopped again to dig another snowpit that gave them the same information as the initial tests. From this location, they had a better view of the slope above and reconsidered their route choice. The top of the slope was blocked by a crevasse band that appeared easy to cross at its extreme left or right. However, they could now see that the winds had been blowing from right to left. Because of these prevailing winds, the left side of the slope was not only more loaded with snow but was also significantly steeper (45-50 degrees). The initial route plan was to stay to the left. However, to avoid the loaded side of the slope, the group decided the safest route was to outflank the crevasse on the right side. This route climbs above an icefall and rock cliffs. At this point, one of the group chose to turn back due to the route's exposure. The remaining three continued up, feeling comfortable with the snow conditions and route choice. The three made steady progress up the slope and reached the right end of the upper crevasse (bergshrund?) band. At this point they were quite close to the summit ridge (perhaps within 100') where the slope levels off significantly. As they crossed the right end of the crevasse, they triggered a small slough that took all three of them over the rock and ice cliffs below. They fell approximately 1,000'. The small, primary slide triggered a larger avalanche lower on the slope. The fracture line for this secondary slide was initially very small but propagated about 50 m across the slope and deepened to about a 1 m slab. Although not involved in the original slough, this debris buried the victims (5cm, 1m, 1m). The other two skiers were nearby and located 2 of their friends quickly (less than 5 minutes), and the third in 10-15 minutes from the time of the avalanche (buried 100m from the other two and in a potentially dangerous location). All 3 sustained significant trauma from the fall/avalanche. The two survivors returned to camp and then over the next 4 days skied out (80 km) and travelled to Bella Coola to start rescue/recovery operations. The group carried an EPERB (Emergency Personal Rescue Beacon) but no radio. The EPERB was not triggered since there was no immediate emergency and the weather was poor, making flying conditions potentially dangerous for search aircraft. In retrospect, the flying conditions in the Cerberus area did not appear to be favorable for the next 3 days. ANALYSIS (by a non-professional): Based on the snow/weather history and the snowpack tests the day of the accident, the decision to climb and the route chosen were sound. Risk from the shear layer observed in the snowpack tests was acknowledged and debated, but was not dramatic or unusual. It is possible that the snowpack changed higher on the slope, and it is likely that local, small-scale effects played an important role. The small primary slide was likely a result of very local snow loading conditions immediately around the crevasse band. Convexities in the slope above the crevasse band were observed from the SAR helicopter, but no fracture lines were visible. However, it is possible that wind may have erased a small fracture. The larger avalanche that was triggered lower on the slope appears to have slid on the ice-layer. This layer is assumed to have shallowed to near-surface depths on the wind-scoured side of the slope that the slough affected. The avalanche did occur around noon, but the day had remained cold (sub-zero) and heavily overcast with the approach of a new front. In addition, even without the heavy cloud cover that was present, the NW exposure, and high cliff walls shield that slope from direct sun until after 12:30. "Greenhousing" conditions related to the cloudcover were not obvious. Therefore, sun combined with slope aspect are not likely to have been a major factor. [Note: An avalanche was reported to occur at the same time of day during the body recovery operation. In fact, 2 small sloughs did occur after the operation was complete (12:30). However, the weather/snow conditions and type of avalanche were completely different than to the accident. The recovery day was one of the first HOT, bright, sunny days in the past 3 weeks. The 2 slides that occurred were small surface sloughs starting from rocks that had been exposed to the sun.] Killed: Brian Waddington, Janet Noakes (Pearson), John Pearson ______________________________________________________ Date: 23 MAY 1996 20:28:31 GMT From: John Nixon Newsgroups: rec.skiing.alpine Three people, 1 woman and 2 men, were killed by the latest coastal range avalanche. The man and woman survivors walked out to Bella Coola, a four day trip, to report the accident. Authorities will survey the conditions on the glacier for possible recovery of the victims bodies. The 2 survivors were said to be in good physical condition, though understandably emotionally distressed. This report came from CBC Radio broadcasts. Jack ______________________________________________________ Date: 28 MAY 1996 23:59:17 GMT From: Ian Wood Newsgroups: rec.climbing Summarized from the Vancouver Sun (on Friday, May 24, Page A1 and A6). Mistakes are probably mine: Three ski-mountaineers were killed in an avalanche on the flanks of Cerebrus Mountain approximately 70 kilometres from the town of coastal town of Bella Coola. They were: Brian Waddington, Janet Noakes and John Pearson. Waddington's wife Betsy Fletcher and Philip (Phil) Hammer survived. The slide occured on day 12 of what was to be a 21-day trip to the Monarch Icefields, as the group were descending the mountain at 12:30 pm. The article did not say what the aspect of the slope was (what direction it faced). Brian Waddington was a geophysicist, Janet Noakes was a family physician in Steveston/Richmond and John Pearson was a Physics instructor at Kwantlen University College (and formerly of the Triumf facility located at the Univ. of B.C.). They were experienced mountaineers. None had children. The sun appears to have been the culprit - when Phil Hammer returned on May 23rd to help authorities recover the bodies, they finished recovering them at 12:15 pm and 15 minutes later another slide let loose. Condolences to the family and friends of the victims. Let's be careful out there... -Ian