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Mapping ground cover using hyperspectral remote sensing after the 2003 Simi and Old wildfires in southern California
Lewis, Sarah A.; Lentile, Leigh B.; Hudak, Andrew T.; Robichaud, Peter R.; Morgan, Penelope; Bobbitt, Michael J.
2007.
Mapping ground cover using hyperspectral remote sensing after the 2003 Simi and Old wildfires in southern California.
Fire Ecology. 3(1):109-128.
Keywords: burn severity, dNBR, erosion potential, hyperspectral data, Relative dNBR, southern California wildfires, spectral mixture analysis, ground cover
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Abstract:
Wildfire effects on the ground surface are indicative of the potential for post-fire watershed erosion
response. Areas with remaining organic ground cover will likely experience less erosion than areas
of complete ground cover combustion or exposed mineral soil. The Simi and Old fires burned
~67,000 ha in southern California in 2003. Burn severity indices calculated from pre- and postfi
re multispectral imagery were differenced (i.e., differenced Normalized Burn Ratio (dNBR)) to
highlight fire-induced changes to soil and vegetation. Aerial and fi eld hyperspectral data were also
collected together with field ground cover measurements soon after the fires. Spectral endmembers
representing green vegetation, nonphotosynthetic vegetation (NPV), charred NPV, and charred
and uncharred inorganic materials (soil, ash, and rock) were used in a constrained linear spectral
unmixing process to determine the post-fire fractional ground cover of each component on the
ground surface. The spectral unmixing results, dNBR, and a Relative dNBR (RdNBR) were
validated using field-measured fractional ground cover estimates to determine which product best
predicted the conditions on the ground. The spectral unmixing results were significantly correlated
to all classes of charred and uncharred organics and inorganics, and the dNBR was the best indicator
of charred soil and green vegetation. The RdNBR had several significant correlations with the
ground data, yet did not consistently correlate well with any specific ground cover types. A map
of post-wildfire ground cover and condition, especially exposed soil and remaining vegetative
cover, is a good indicator of the fire's effect on the ground surface and the resulting potential for
hydrologic response.
Moscow FSL publication no. 2007k
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