Snow Crystal

SNOW HYDROLOGY (GEOG 4321): HOMEWORK ASSIGNMENT 4

Instuctor: Mark Williams
Telephone: 492-8830


Homework 4

  1. Draw a schmatic diagram of a slab avalanche, label the various parts, and also label where these forces are most likely to be found: tension, compression, and shear. 5 pts.
  2. Why are small gullies called terrain traps with respect to avalanche danger? Be sure to address in your answer: slope angle, exposure, wind, runout zones, and lack of perceived danger. 5 pts.
  3. Calculate the shear stress in N/m2 in a snowpack given the following parameters:
    1. density = 250 kg/m3; snow height = 1 meter; and slope angle = 30 degrees.
    2. Change the slope angle to 45 degrees. What is the shear stress? What is the precentage change in the shear stress caused by the increase in slope angle?
    3. Do the same calculation as in b, but increase snow density and snowpack depth: density = 450 kg/m3; snow height = 2.5 meter; and slope angle = 45 degrees. What is the shear stress? What is the precentage change in the shear stress caused by these changes compared to problems a and b? 10 pts.
  4. What is the maximum velocity and impact pressures of avalanches in the following situations?
    1. An open slope, slope angle of 35 degrees, flow depth of 2 meters, a flowing density of 150 kg/m3, mu = 0.3, and coefficient of turbulent friction of 750 m/s2.
    2. Same situation, but a rocky slope? note the coefficient of turbulent friction is 500 m/s2 for rocky slopes.
    3. An open slope, slope angle of 50 degrees, flow depth of 2 meters, a flow density of 500 kg/m3, and mu = 0.2. 10 pts.
  5. The local forecast states that a recent storm has deposited champagne powder on the Continental Divide: 1 meter of new snow with a density of 80 kg/m3. You and a group of friends have decided to head out into the backcountry and put first tracks on a great bowl near Berthoud Pass, which has an angle of 40 degrees. Before leaving Boulder, the wind picks up and is blowing 20 m/s. Describe how you would use this information to decide which slopes to ski. Once you arrive at Berthoud Pass, what other steps might you take to evaluate the stability of the slope before skiing? One page maximum. 10 pts.