A NEW AVALANCHE HAZARD MAP FOR SALT LAKE COUNTY

To address aggressive development in mountain and foothill areas, Salt Lake County has updated its geologic hazards ordinance and zoning maps to add requirements for engineering geology studies in landslide, debris flow, rockfall and avalanche hazard areas. The revised ordinance includes developing a new avalanche hazard special study area map (AHM) of avalanche influence zones (AIZ), and also includes requirements for site-specific avalanche hazard analyses for land use proposals within those AIZs. The AHM includes the combined product of known avalanche paths, along with delineations of new AIZ boundaries based on digital terrain analysis, stereoscopic aerial photographs, field observations, and historical research. County land use planners will use the AHM to assist in decision making about whether to require site-specific avalanche hazard analyses. Site-specific avalanche hazard analyses will include detailed studies of topography, geography, vegetation, site conditions, current and historical snowpack conditions, and weather patterns; provide estimates of return frequency and estimated impact forces; and delineate avalanche red zones (in which structures would be prohibited), and avalanche blue zones (where buildings may be permitted only with appropriate mitigation).