Characterizing drainage flows that result in smoke intrusions from prescribed burning

Prescribed burning (Rx) is carried out to improve forest health, create a diversity of plant and wildlife habitat and to protect communities and quality of life. Federal land management policies are particularly focused on treating acres in the Wildland Urban Interface (WUI) to protect communities from the devastating effects of wildfire. These treatments include prescribed burning. Simultaneously, State and Federal regulations and policies prohibit allowing smoke to be carried into nearby populated areas (referred to as smoke-sensitive areas). The nature of prescribed burning when coupled with complex terrain leads to a variety of challenges. Not only does the meteorology vary between day and night in this area, but smoke emissions vary as well depending upon the types of fuels, type of burning, fuel loading, and flaming vs smoldering stages of fires. During the day, when the flaming stage occurs, the challenge is to keep smoke from being directly transported into smoke sensitive receptor areas. At night, the nocturnal inversion sets up, trapping emissions from the smoldering stages of fires, which can lead to smoke being transported along river drainages directly into towns. The complex terrain makes it particularly difficult to predict when smoke from fires, sometimes many tens of miles away, will be transported into smoke sensitive areas.

The Forest Service Region 6 Air Program and the PNW Research Station AirFire Team are collaborating with land managers on a project to gain a better understanding of meteorological conditions on the Deschutes National Forest near Bend, Oregon so as to increase the pace and scale of forest restoration burning while protecting air quality in Bend and surrounding communities.. We have deployed a number of weather stations (which measure wind speed and direction, temperature, and RH), and three portable air quality particulate monitors (E-Samplers, which measure PM2.5 or particulate matter less than 2.5 micrometers in diameter, and wind speed and direction). Two automated cameras were also deployed at wildfire lookout points. Instruments were deployed for the Fall 2014 prescribed burn season, five weather stations remain in-place over the winter when pile burning occurs, and the remaining instruments (E-Samplers and cameras) were re-deployed for the Spring 2015 Rx burn season. We also simulated dispersion from actual and hypothetical prescribed fires at spatial resolutions of 4km and 1km.