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* Metric Name: Source of Ember Load to Buildings  

* Tier: 1  

* Data Vintage: 08/2023. Includes disturbances through the end of 2022.  

* Unit Of Measure: Relative index  

* Metric Definition and Relevance: The ember transport model used in WildEST tracks the travel of embers from each source pixel to downwind receiving pixels. The relative number of embers landing on a given receiving pixel is summed across all potential source pixels. If the receiving pixel has a nonzero WRC Building Cover value (meaning the pixel is within 75 m of a qualifying building), then we separately sum the relative number of embers from the source pixel. The final SELB raster represents the expected annual relative ember production that lands on building cover across all weather types.  

* Creation Method: The WildEST modeling contains a module for producing indices of conditional and expected ember production and load. The Conditional Ember Production Index (cEPI) is an index of the relative number of embers lofted at a given landscape pixel given the fire environment there, given that a fire occurs. Ember Production Index (EPI) is the expected value of cEPI; it is the expected annual relative number of embers lofted from a given landscape pixel.

The Conditional Ember Load Index (cELI) is a relative index of the relative
number of embers that land at a given landscape location, including
nonburnable pixels. Finally, Ember Load Index combines the conditional ELI and
the likelihood of that ember load occurring. All ember characteristics are
based on headfire behavior. These

The ember load indices represent relative ember load at a pixel. Similar to
ember production, ember load is also based on surface and canopy fuel
characteristics, climate, and topography at the pixel. Ember load incorporates
downwind ember travel.

The Ember Load Index (ELI) incorporates burn probability; however, ELI is not
simply the multiplication of condition ember load (cELI) and burn probability
(BP). Rather, BP is incorporated into calculations of the ember production
before the distribution of embers across the landscape to determine ember
load. Given that ELI incorporates burn probability, this index can be used to
identify where on the landscape hardening buildings may be needed to resist
ignition and the priority for doing so according to the likelihood of the area
being visited by fire.

  

* Credits: Pyrologix, LLC \--James Newman (California State BLM Office) jnewman@blm.gov