Using GIS to determinate a suitable areas for avalanche occurrences in

the Presidential Range, New Hampshire, USA

Silvia PetrovaObjective

Several factors may affect the likelihood of an avalanche including weather, temperature, slope steepness, slope orientation, wind direction, terrain, vegetation and

snow pack condition. Different combination of these factors can create a low , a moderate or an extreme avalanche condition.

The objective of this project is to use Geographical Information Systems to map avalanche risk zones in the Presidential Range in the White Mountains in New

Hampshire based on topographical and vegetation parameters . The DEM, with 30 meter resolution, has been used to create topographic variables such as slope,

aspect and to extract runoff accumulation per pixel. Land use map from 2001 has been used to determine the forest areas in order to constrain the possible sites for

occurring of avalanches. Although the avalanche can occur on any slope given the right condition, certain locations are naturally more dangerous than others. Existing

avalanche sites supplied from Appalachian Mountain Club have been use to determine the accuracy of the results.

Predicted Suitable Avalanche Sites

Land cover map

Forest- non forest map

Morphological and terrain factors Vegetation Constraint

Methodology

Multi - criteria evaluation process has been applied to

identify avalanche hazard zones.

Three factors have been use :•Elevation greater the 650 meters;•Slope greater than 25 degrees; •1000 meters from the bed of the gullies;

The result has been constraint by :•Areas with low vegetation .

Two procedures are common for MCE. The first involves

the Boolean overlay where all criteria are needed to meet

the suitability logic. The second is known as Weighted

Linear Combination , where factors are standardized then

combined according their weights.The result is a suitability

map which is masked by the Boolean constraint.

Modules such as PCLASS and FUZZY were used to

create suitability maps of slope and elevation. Modules

RUNOFF and DISTANCE were used to determine the

gullies (areas where the aspect change rapidly) and

calculate distance from these areas. RECLASS module

was used to determine open area and forest area. All

factors and constrains were plugged into the multi-criteria

decision wizard. The factors were weighted equally to

create suitability sites for avalanches.

DEM - Elevation Slope

Slope greaterthan 25 degree

Terrain - gullies

Distance-runoff

1000 m from the bed of the gullies

Elevation greater than 650 m

Conclusion

The Presidential Range of New Hampshire is an unusual mountain environment in the

Eastern United States. It is considered as the most dangerous small mountain range in

the world. Although, the range has a greatest concentration of avalanche terrain and

severe weather condition, it is a preferable place for winter recreation.

Using the MCE decision making procedure incorporated in Idrisi, it is possible to define

the risk avalanche areas based on topographic factors and vegetation constraints.

Considering the elevation, slope steepness , terrain and vegetation cover, it is possible to

update an existing avalanche locations.

An avalanche in motionSource:http://nsidc.org

The highest peak is Mt Washington (1916m). While severe winter weather

is commonly acknowledged, much less is known about the avalanche

terrain. Since 1954, there have been 10 avalanche fatalities as well as

many other avalanche accidents in the Presidential Range.

Study Area The Presidential Range in the White Mountains of

New Hampshire has the greatest concentration

of avalanche terrain east of the Rocky Mountains

in the United States.

Tuckerman Ravine, is famousfor its scenery, deep snow, hiking and skiing terrain.

Acknowledgments

This research has been performed in Idrisi Kilimanjaro with the data from: •NH GRANIT Web Site;•Appalachian Mountain Club .

Known Avalanche areas were used for validating the Predicted Suitable Avalanche sites. The Crosstab module result is shown to the right. An area of 9.5 km2 from the existing sites was predicted from the MCE module. This is two –thirds of the area of 14.9 km2 existing avalanche sites.