Assessing Potential Safety Zone Suitability using the Safe Separation Distance Evaluator (SSDE)

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Safety zones are fundamental tools that can be used by wildland firefighters to avoid injury or fatality when engaging in wildland fire operations. The National Wildfire Coordinating Group (NWCG) recommends that a safety zone be defined as a pre-planned area of sufficient size and suitable location that is expected to prevent injury to fire personnel from known hazards without using fire shelters. Currently, safety zones are primarily designated by fireline personnel as part of daily fire management operations. Though critical to safety zone assessment, the effectiveness of this approach is inherently limited by the individual’s ability to accurately and consistently interpret vegetation conditions, topography, burning conditions and spatial characteristics of potential safety zones (e.g. area and geometry of a forest clearing). Regardless, effective safety zones provide safe separation distance (SSD) from surrounding flames, ensuring that the surrounding heat cannot cause burn injury. We introduce a new online tool for mapping SSD based on vegetation height, terrain, wind speed, and burning conditions: the Safe Separation Distance Evaluator (SSDE). The new tool allows users to draw a potential safety zone polygon and estimate SSD and the extent to which that safety zone polygon may be suitable, given the local landscape, weather, and fire conditions. The SSDE tools calculates separation distance based on vegetation height, wind and slope adjustment factors and burning conditions. Fuels layers are imported for LANDFIRE Existing Vegetation Height. Slope is calculated from the Shuttle Radar Topography Mission (STRM) digital elevation model. Winds are derived from the local fire weather forecast. Burning conditions are based on fuel moisture, relative humidity, and temperature. The Safe Separation Distance Evaluator (SSDE) algorithm is built and applied in Google Earth Engine (GEE), a cloud-based platform for processing and analyzing GIS and remotely sensed data, using JavaScript application programming interface. SSDE is a tool that can provide valuable safety information to wildland fire personnel who are charged with the critical responsibility of protecting the public and landscapes from increasingly intense and frequent fires in a changing climate.