LEVEL 1 - AVALANCHE OVERVIEW HANDOUT

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1 Bill Glude Alaska Avalanche Specialists All photos and graphics Bill Glude unless otherwise noted. LEVEL 1 - AVALANCHE OVERVIEW HANDOUT Summary of Key Points Statistics 1

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4 Urban Avalanches Juneau 62 houses, 1 hotel, 2 sections of the Egan Expressway and Glacier Highway, 8 residential streets, and much of Aurora Basin boat harbor in avalanche zone, 1962 slide was only a 30-year event. Encouraging steps taken but still inadequate. Major paths affecting houses: Behrends Avenue and White Subdivision Paths. Cordova Slide at 5.5 Mile, , 100-year urban event, a similar slide in Juneau would be likely to kill at least 100 people. Steps taken: relocation, inadequate volunteer forecast. Other Alaskan Communities Valdez, Anchorage, Girdwood, Moose Pass, Kennicott, and other Alaskan communities have urban avalanche issues. The houses in the main avalanche area in Valdez were moved after the year 2000 avalanche cycle. Steps taken: relocation, inadequate volunteer forecast. Roads and trails Gold Creek urban trails Mt. Juneau paths and Snowslide Gulch affect the Flume, Perseverance Trail, and Basin Road. Roads and trails, Thane Road 20+ paths; Snowslide Creek (most frequent), Middle, and Cross Bay Creek Paths are all quite active. Industrial areas Roads, railroads, power plants and lines, mines, construction, logging, ski areas, guiding operations. Other avalanche hazard areas Trails, snowmachine areas, ski areas, out-of-bounds, heliski areas, snowkiting areas, and backcountry. Types of avalanches The main two: slabs and point releases, loose snow avalanches, or sluffs. The special types: cornice collapse, glide avalanche, roof avalanche, slush flow, ice avalanche. The Decision-making Triangle Factors: terrain, snowpack, weather, human. Traffic light: red, yellow, or green light conditions. Or +, 0 and - if you want to be able to sum your factors. The Helms Deep analogy There are three walls to the avalanche castle, just as the Helm s Deep fortress in J.R.R. Tolkien s The Two Towers had three walls. You need all three walls. No one wall will protect you. The outermost wall is stability evaluation. It s a good wall to have, and will save you on many days, but it s a tough skill. You will inevitably blow your stability evaluation and that wall will be breached by the avalanche orcs. 4

5 The second wall is your risk management procedures, all the route-finding, consequence evaluation, travel ritual, training, and preparation things you do to minimize risk every day in the mountains. This wall is the one that has the greatest potential to save you from the avalanche orcs. The final wall, the keep of the castle, is rescue, your last defense. And in real life as in the story, you do not save yourself. When you are caught and buried, it is not your skills that will save you, but Gandalf on a shining horse who appears in the form of your buddies with beacons, probes, shovels, and the skills to use them. So get your friends trained! Outline Juneau-area urban avalanche paths Current tally: 62 houses, 1 hotel, 2 sections of Egan Expressway and Glacier Highway, eight streets, and much of Aurora Basin boat harbor in avalanche zone, 40 houses in severe hazard zone and 22 plus the hotel in moderate hazard zone. Still virtually no regulation except prohibition on multi-family or rental construction, but CBJ has prepared an avalanche response plan, trained response crews, has begun a voluntary buyout and relocation program, and has begun a still-underfunded forecasting program that has potential but is not yet meeting standards for reliability. Buyout or fixed remotecontrolled exploders, likely in combination with a system of braking mounds and catching dams, are the best long-term options. 5

6 The urban paths are infrequent-running but have huge destructive potential. None of the avalanches since the houses were built has come anywhere near the capability of the paths. We have seen only 30 year events for far, no 100 or 300 year events. There are also some unmapped paths above Gastineau Avenue and Starr Hill which will slide in exceptionally heavy snow years. Steps taken: response plan developed, response groups trained, voluntary buyout and relocation begun, forecasting program begun but underfunded, understaffed, not operating for full season, lacks field presence, fieldwork infrequent. Encouraging steps taken but still inadequate. Behrends Avenue Path 14.4 year return interval (Mears, Fesler, & Fredston 1992), infrequent but large, 42 houses, 31 in severe hazard, 1 hotel in moderate hazard zone, harbor in moderate hazard zone, largest slide in 1962, four streets, Old Glacier Highway, and Egan Expressway exposed. White Subdivision Paths 3.6 year return interval (Mears, Fesler, & Fredston 1992), smaller but more frequent, 20 houses, 9 in severe hazard, four streets exposed. plus White Path can cross both Old Glacier Highway and Egan Expressway. Mt. Juneau Paths, Gold Creek Bathe Creek, Flume, Gnarly, Chop Gully, Green Weenie, and Sunshine Paths affect the Flume, Basin Road, and lower Perseverance Trail. 6

7 Snowslide Gulch, Gold Creek Most frequent-running large path in the area. Affects Gold Creek and the A-J Mine drainage tunnel, dusts Perseverance Trail and the Mining Museum footbridge. Can run big late in season, dammed Gold Creek and flume ran dry. Thane Road Paths 20+ paths, Snowslide Creek has 1.2 year return interval, Middle and Cross Bay Creek Paths also notable. Has explosives delivery program with 105mm howitzer fired from near Sandy Beach, currently no forecasting program. Dusted school bus twice in February

8 Other notable urban avalanche areas in Alaska Cordova Slide at 5.5 Mile, , 100-year urban event. One killed, one extricated and revived from cardiac and respiratory arrest. A similar slide in Juneau would be likely to kill at least 100 people. Houses in severe hazard zone were relocated after year 2000 slide. There is a volunteer forecast program but it is lacking in field presence, fieldwork appears irregular. Other Alaskan towns Valdez, Anchorage, Girdwood, Moose Pass, Kennicott, and other Alaskan communities have urban avalanche issues. Good tallies of their numbers and locations are not available. The houses in the main avalanche area in Valdez were moved after the year 2000 avalanche cycle. There is a volunteer forecast program but it is lacking in field presence, fieldwork appears infrequent, focus is on recreational users. 8

9 Industrial areas Roads, railroads, power plants and lines, mining, construction projects, logging, quarries, ski areas, guiding operations...wherever people live and work in avalanche paths. Alaskans are much more at risk from this kind of exposure then are people in most other states. Highways The Seward, RIchardson, Dalton, Copper River, Haines, and Klondike Highways and Thane Road, are all affected by avalanches. The proposed Bradfield Canal and Lynn Canal highways would be affected. Other avalanche hazard areas Ski areas Out-of-bounds backcountry near ski areas Heliski areas Trails Snowmachine areas Snowkiting areas. Backcountry Types of avalanches Two main types Point releases, sluffs, or loose snow avalanches. Different names for the same thing. A few grains move and dislodge more, the slide fans out. It involves only the surface layers and has indistinct boundaries. Sluffs can be wet or dry. Slab avalanches. A layer or group of layers releases over a relatively large area with well-defined boundaries and bed surface. Slabs can be wet or dry. Special types Cornice collapse. Assume cornices are present on any snow-covered ridge until proven otherwise. Cornices break more easily and farther back than you would expect. Overhang is likely between visible rocks or ground. The fall can be dangerous, the cornice may trigger the slope, and the falling blocks are hazardous, too. Glide avalanche. These occur when the entire snowpack is sliding on the ground. Glide cracks form as tension cracks, like crevasses on a glacier. The snow may glide and rumple slowly with no release or may fracture as a full-depth avalanche. Their release is unpredictable. There is no real weather connection, except that they do release more during heavy rain. Mostly, they are like a person hanging onto roof by their hands, they let go when they get tired of hanging on. Roof avalanche. Can be huge and they do kill people. Difficult to predict. Stay clear, sign or rope off affected areas! Slush flow. Generally in an interior or arctic climate, at high latitude. Weak snowpack develops in winter cold with lots of week sugary faceted grains, rapid change in length of day and rapid warming causes snowpack in gullies to become water-saturated. Fractures as a wet slab, then liquefies to slurry with rocks and dirt. Can release on 12 and travel 19m/sec (40mph) on 3 to 4 slope. Ice avalanche. By ice we mean glacier ice. These occur when hanging ice, seracs, or gliding blocks detach and fall. They have a large scale and long runout. They may trigger a snow as well. They are unpredictable. Glaciers flow all winter, and all night. There is no dependable cycle. If you feel you have to go through areas threatened by ice avalanches, first reevaluate whether you really have to. 9

10 If you go, use whatever periodicity you think they may have, invoke the deity of your choice, and go like hell! Decision-making triangle, key questions Terrain 1. Could the slope slide? 2. Where you are? 3. Above you? 4. And what would the consequences be? Snowpack Could the snow release? Weather Is the weather contributing to instability? The decision-making traffic light These decision-making triangle factors are just being introduced in this talk. They will be used as the framework for the rest of the course, and we will go into all of them in much greater detail. An alter- 10

11 nate method is to use +, 0, and - to rate factors. This option allows the various factors to be summed into one number. 11

12 The Helm s Deep Analogy 12

13 And Gandalf appears in real life in the form of your buddies equipped with beacons, probes, shovels, and the skills to use them! Graphics are from the Lord of the Rings movies website. 13