Abstract

Communities are encroaching rapidly along the base of the steeply rising Wasatch Mountains because of the high quality views found there. The increased growth has significantly increased the risk of wildfire damage. This study includes the cities between North Salt Lake and Pleasant View, Davis and Weber Counties, Utah.

Wildfires are only the initial hazard. Fire makes the burned areas susceptible to hazards from the next intense storm flow. The resultant excessive sediment delivery represents a significant hazard to downstream urban areas. The main objective of this study was to provide quick access to quantitative post-fire sediment delivery data for cities and counties. This will facilitate a rapid response in post-fire emergency mitigation action. Previously, these assessments took from two to ten days to complete.

Geographic Information System layers were developed to deliver this procedure to city and county planners and emergency response staffs. Sediment yield rates were developed for each individual canyon-fan drainage way and the interfluve areas for the before-fire, post-fire low intensity burn and post-fire high intensity burn conditions. The layers of information developed for this study include sediment yield, slope failure, vegetation, soil, slope and watershed sub-basins. These GIS databases can be updated in the future and can also be manipulated for more detailed analysis of natural resources or hazards.

Sponsorship for the project came from cities, towns, counties, and the State of Utah, Division of Comprehensive Emergency Management. Funding for the study was developed through the River Basin Program of the United States Department of Agriculture, Natural Resources Conservation Service.

The use of a Geographic Information System in this assessment will save critical reaction time during the post-fire hazard mitigation assessments. Damage potential was based on sediment yield volume and a risk assessment rating of low, medium or high was developed.