BSU avalanche research to help ITD forecasting 

Avalanches routinely occur on Idaho 21 between Lowman and Stanley each winter, which poses a threat to the safety of ITD maintenance workers and the traveling public.  Boise State University (BSU) researchers Scott Havens, Hans-Peter Marshall, and Jeffery Johnson are developing tools for ITD avalanche forecasters to incorporate into their daily avalanche forecasting operations. 

BSU is working on two research projects funded through ITD’s Research Program to support avalanche forecasters. First, development of a near-real time, operational avalanche forecasting model for Idaho 21 and U.S. 12, and second, development of real-time avalanche detection for high-risk areas along Idaho 21.
The near-real time, operational avalanche forecasting model for Idaho 21 and U.S. 12 implements the SNOw Slope Stability (SNOSS) model developed by Conway and Wilbour (1999).

SNOSS is a simple, one-dimensional avalanche forecasting model comparing the overburden shear stress caused by new snow to the strength throughout the snowpack. 

SNOSS is used operationally on Interstate 90 at Snoqualmie Pass, Wash., and on the Milford Road in New Zealand. 

The underlying theory of SNOSS is to approximate density through the snowpack using a densification model, and then estimate the strength profile from the density. 

Avalanches are expected to occur in a region when the stress from the new snow exceeds the strength at any depth in the snowpack.  Improvement of the densification model, tuned to Idaho 21 and U.S.12, will provide an avalanche forecasting tool that ITD forecasters can consult when evaluating avalanche hazard.
Detection of avalanches along Idaho 21 is achieved using multiple infrasound arrays.  Avalanches emit infrasound (sound below the human threshold of hearing) in the 1-10 Hz region. Because of the low frequencies, the signal can travel for large distances. 

Infrasound is used operationally at Teton Pass, Wyo., and Little Cottonwood Canyon, Utah, by avalanche forecasters to determine when and where avalanches occur in their most problematic slide paths. 

BSU has deployed infrasound arrays for the past two winters, capturing many avalanche and non-avalanche events along Idaho 21. The detection project builds and complements SNOSS modeling as accurate timing of an avalanche can be determined from the infrasound signal. Information will help calibrate and validate SNOSS to the Idaho 21 corridor.
Avalanche detection will benefit ITD and the rural communities influenced by the Idaho 21 corridor. With the installation of the proper instrumentation, ITD avalanche forecasters will have an operational real-time avalanche detection system that can be consulted remotely to determine if avalanches have occurred along the Idaho 21 corridor.

The regional avalanche activity can be evaluated through detection of small avalanches high in the avalanche start zones that do not affect the road. This will be the third such installation in the U.S.

The system has the ability to expand the avalanche detection network to include more arrays throughout Idaho 21 and Idaho, with the main focus on developing U.S. 12. Reducing road closures will help to prevent economic losses to small businesses in Stanley and Lowman.
The research performed by BSU along Idaho 21 will result in the development of tools for ITD avalanche forecasters to detect avalanche activity of any size and to assist in forecasting of new snow avalanching.
Bill Nicholson, District 3 Maintenance, is the ITD project manager for the research. The Technical Advisory Committee includes Chantel Astroga, Inez Hopkins, Bob Koeberlein, Tom Points, Mike, Ponozzo and Craig Schumacher.

Published 2-8-2013