CE 394 K - GIS in Water Resources

CE 394 K.3

Semester Project Outline

Avalanche Hazard Forecasting Using GIS

Department of Civil Engineering University of Texas at Austin  

Fall 1999  

djanderson@mail.utexas.edu  

Background

Complex relationships exist between terrain, climate, and snowfall in the mountainous regions throughout the United States.  The combination of periodic precipitation (in the form of snowfall), cold and windy climates at high altitudes, and steep terrain make the conditions right for layers of snow parallel to the ground surface to experience significant shear stresses, triggering an avalanche.

The weather is the most important factor in determining whether avalanches are likely, and the evaluation of the snowpack is entirely dependent on this. Many weather variables affect avalanche release, such as air temperature, wind speed and direction, and precipitation rate and quantity.  The net radiation at the snow surface is another piece of information critical to accurately determining potential avalanche conditions.

The following snowpack conditions also affect the probability of an avalanche:

Any of the above conditions might be the source of a dangerous weakness in the snowpack, and when combined with data on the snow itself, such as snow settlement rate, snow density, and water equivalent values througout the snow horizons, a shear plane can be detected on which the snow above will have a tendency to slide.

Finally, terrain is obviously important when forecasting avalanche conditions.   The steeper the slope, the greater the tendency for an avalanche.  The more trees, however, the less likely an avalanche will begin.  Slope profile is also important; convex slopes are generally more hazardous than uniform or concave slopes.   The point of maximum convexity is a frequent site of tension fractures, with the release of slab avalanches.

Much of the data listed above is available on the Internet for public use.   By mathematically analyzing the different variables that, together, comment on the likelihood of an avalanche, and combining the results and distributing them spatially using a GIS, one should be able to create a map of high-medium-low avalanche hazard areas for areas where data is available.

Objectives

The objective of this project is to create a map that presents high, medium, and low avalanche hazard areas for a particular region of the intermountain west (the Rocky Mountains).  I intend to research snow and avalanche mechanics textbooks and previous attempts at avalanche forecasting to determine the theoretical relationships between the variables presented above.  From these relationships, I should be able to use downloadable regional data (i.e., DEMs, recipitation grids, temperature grids), perhaps combined site specific snowpack data, and determine which sites may be more susceptible to avalanches than others.  Then, using GIS again, I should be able to present a map of a particular region, with the avalanche hazard areas delineated accurately.

Information Sources