Avalanche

An Avalanche is a mass of snow in swift motion traveling down a mountainside.

In the National Risk Index, an Avalanche Risk Index score and rating represent a community's relative risk for Avalanches when compared to the rest of the United States. An Avalanche Expected Annual Loss score and rating represent a community's relative level of expected building and population loss each year due to Avalanches when compared to the rest of the United States.

A map of the United States colored by Avalanche Risk Index ratings. Avalanche risk is concentrated along the Rocky Mountains, Sierra Nevada Mountains, Cascade Mountains, Brooks Range, and Alaska Range. For full results, see the National Risk Index Map webpage.

Click to view map Data Download

Avalanche Exposure

An Avalanche exposure value represents a community's building value (in dollars) and population (in both people and population equivalence) exposed to Avalanches.

Avalanche Annualized Frequency

An Avalanche annualized frequency value represents the average number of recorded Avalanche hazard occurrences (events) per year over the period of record (60 years).

Source Data

National Avalanche Center's Avalanche Forecast Zone Map

Arizona State University's Center for Emergency Management and Homeland Security's Spatial Hazard Events and Losses Database of the United States (SHELDUS)

Avalanche Historic Loss Ratio

An Avalanche historic loss ratio is the representative percentage of the exposed consequence type value (building or population) expected to be lost due to an Avalanche hazard occurrence.

Avalanche Processing Methodology

For comprehensive details about the Avalanche processing methodology, see the National Risk Index Technical Documentation.

View Disclaimer