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Movement of Sediment Through a Burned Landscape:Sediment Volume Observations and Model Comparisons in the San Gabriel Mountains, California, USA.
Lewis, S.A.; Robichaud, P.R.; Hudak, A.T.; Strand, E.K.; Eitel, J.U.H.; Brown, R.E. 2021.
Evaluating the Persistence of Post-Wildfire Ash: A Multi-Platform Spatiotemporal Analysis..
Fire 4,68. DOI: 10.3390/fire4040068.
Keywords: post-fire; remote sensing; wildfire ash; spectral indices; Sentinel-2; hydrologic response
Links:
PDF 6,526 KB]
Abstract:
As wildland fires amplify in size in many regions in the western USA, land and water
managers are increasingly concerned about the deleterious effects on drinking water supplies.
Consequences of severe wildfires include disturbed soils and areas of thick ash cover, which raises
the concern of the risk of water contamination via ash. The persistence of ash cover and depth
were monitored for up to 90 days post-fire at nearly 100 plots distributed between two wildfires
in Idaho and Washington, USA. Our goal was to determine the most ‘cost’ effective, operational
method of mapping post-wildfire ash cover in terms of financial, data volume, time, and processing
costs. Field measurements were coupled with multi-platform satellite and aerial imagery collected
during the same time span. The image types spanned the spatial resolution of 30 m to sub-meter
(Landsat-8, Sentinel-2, WorldView-2, and a drone), while the spectral resolution spanned visible
through SWIR (short-wave infrared) bands, and they were all collected at various time scales. We
that found several common vegetation and post-fire spectral indices were correlated with ash cover
(r = 0.6–0.85); however, the blue normalized difference vegetation index (BNDVI) with monthly
Sentinel-2 imagery was especially well-suited for monitoring the change in ash cover during its
ephemeral period. A map of the ash cover can be used to estimate the ash load, which can then be
used as an input into a hydrologic model predicting ash transport and fate, helping to ultimately
improve our ability to predict impacts on downstream water resources.
Moscow FSL publication no. 2021i
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