Risk of Avalanches

From FEMA's National Risk Index: An Avalanche is a mass of snow in swift motion traveling down a mountainside. 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)源自美国联邦紧急事务管理局（FEMA）国家风险指数：雪崩（Avalanche）指沿山坡快速移动的大规模积雪团。雪崩年化频率值代表统计周期（60年）内记录到的雪崩灾害事件年均发生次数。本数据集源数据包括：美国国家雪崩中心的雪崩预报区地图，以及亚利桑那州立大学应急管理与国土安全中心的美国空间灾害事件与损失数据库（Spatial Hazard Events and Losses Database of the United States，简称SHELDUS）。