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

Abstract

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 0.20ms-1, respectively, for the 4months immediately following the fire and 10 and 0.55ms-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 1495kgm-1 of horizontal sediment transport within the first 2m above the soil surface, had a maximum PM10 vertical flux of 100mgm-2s-1, and generated a large dust plume that was visible in satellite imagery. The peak PM10 concentration measured on-site at a height of 2m in the downwind portion of the burned area was 690mgm-3. Our results indicate that wildfire can convert a relatively stable landscape into one that is a major dust source. © 2012.