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.
Highlights
Consistent and accurate mapping of wildland fires is a critical function for active fire management as well as for post-fire mitigation and monitoring regimes
Transects 3–6 generally had lower mean ash cover at all points in the study period compared to T1 and T2, as expected due to their lower burn severity
To evaluate if the blue normalized difference vegetation index (BNDVI) may be suitable for mapping or monitoring ash more uniTo evaluate if the BNDVI may be suitable for mapping or monitoring ash more versally, we extended our analysis to include data from the 2017 Redford Canyon Fire
Summary
Consistent and accurate mapping of wildland fires is a critical function for active fire management as well as for post-fire mitigation and monitoring regimes. Wildfires play important ecological and hydrological roles in forests and have become larger and more frequent in the western USA in recent years [1]. This trend is expected to endure as summers continue to be longer and drier, and the effects of fire suppression and wildland–urban interface (WUI) encroachment persist in many regions [2,3,4]. Wildfires combust organic matter into ash or char ranging from gray or white non-aggregate or airy materials to black, charred, and semi-recognizable organic matter. The presence of ash cover indicates combustion at high temperatures and long fire residence time [9,10,11]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
