Wind erosion from a sagebrush steppe burned by wildfire: Measurements of PM10 and total horizontal sediment flux

Wind erosion and aeolian transport processes are under studied compared to rainfall-induced erosion and sediment transport on burned landscapes. Post-fire wind erosion studies have predominantly focused on near-surface sediment transport and associated impacts such as on-site soil loss and site fertility. Downwind impacts, including air quality degradation and deposition of dust or contaminants, are also likely post-fire effects; however, quantitative field measurements of post-fire dust emissions are needed for assessment of these downwind risks. A wind erosion monitoring system was installed immediately following a desert sagebrush and grass wildfire in southeastern Idaho, USA to measure wind erosion from the burned landscape. This paper presents measurements of horizontal sediment flux and PM10 vertical flux from the burned area. We determined threshold wind speeds and corresponding threshold friction velocities to be 6.0 and 0.20 m s−1, respectively, for the 4 months immediately following the fire and 10 and 0.55 m s−1 for the following spring months. Several major wind erosion events were measured in the months following the July 2010 Jefferson Fire. The largest wind erosion event occurred in early September 2010 and produced 1495 kg m−1 of horizontal sediment transport within the first 2 m above the soil surface, had a maximum PM10 vertical flux of 100 mg m−2 s−1, and generated a large dust plume that was visible in satellite imagery. The peak PM10 concentration measured on-site at a height of 2 m in the downwind portion of the burned area was 690 mg m−3. Our results indicate that wildfire can convert a relatively stable landscape into one that is a major dust source.

► PM10 flux and horizontal sediment flux are reported following a wildfire.
► Wildfire can convert stable landscapes into major sources of particulate emissions.
► Threshold velocities and friction velocities are reported for 1 yr post-fire.
► Ratios of PM10 to horizontal soil flux were on the upper end of reported values.
► Gradient transport theory should be applied above the zone of horizontal transport.