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The Nature Conservancy in Michigan Michigan About Michigan Contact Places We Protect Science Volunteer Ways of Giving In The News Slide Show Events |
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© TNC/Jack McGowan-Stinski |
By Jack McGowan-Stinski
Michigan Fire Manager, The Nature Conservancy
Week 3: Science of the Sleeper Lake Fire
Thursday, August 23-Wednesday, August 29, 2007: Newberry, Michigan
The Sleeper Lake fire is now 80% contained due to the hard work of the dedicated individuals at the MDNR. They keep an eye on all potential wildfires throughout the fire season and use a lightning map to track areas struck. A staff member could look at this data and tell you every spot hit by lightning in Michigan this year.
The MDNR also have a drought code to help monitor potential conditions for a wildfire. In the spring, when the ground is saturated with snow melt, the drought code registers zero. This goes up incrementally as things dry out. Staff begin to feel concern at about 300, while 500 is considered deep and serious drought. Sleeper Lake set a record with a drought code that topped over 600. Heavier fuels such as larger logs and trees that wouldn’t easily burn because they are too wet and big now ignite and burn completely. Peat (organic soil) that is normally saturated to the point that it will seldom ignite, now is burning 2-3 feet or deeper under the surface. The peat is so dry that dozers and ATV’s can drive (track) over the surface without gettig mired down, except where the surface has been cleared.
Wildfires the size of Sleeper Lake remain rare because the mix of these habitats are usually too wet and green this time of the year to burn over extensive areas, but the extreme drought exacerbated fuel conditions. When lightning strikes, the ground could smolder for days waiting for the right wind and humidity conditions. The surface fire can then spread elliptically unless it reaches a change in fuel. The main fire often spreads more rapidly due to embers spotting out ahead into available fuel, making containment difficult. The Sleeper Lake fire occasionally saw winds of 30 miles per hour.
The head of the fire is the portion of the main fire that is “pushed” along by the wind, which is also often the hottest and fastest part of the fire. The back (rear) and the flanks (sides) of the fire burn more slowly against the wind, resulting in an elliptical shape. Whenever possible, fire crews start the initial attack on the fire from the safer backing and flank areas. Crews then try to suppress the flanks and “pinch” off the headfire. Often indirect suppression is needed to avoid exposing firefighters to dangerous conditions.
Right from the start, the Sleeper Lake fire posed containment problems because of its location. The lightning strike was in a remote area of the wetland with no good access roads. Fire equipment kept sinking into the muck and there were areas with dense timber that made even walking difficult. CL-215 water bombers were used to cool down hot areas, but due to the drought conditions, the fire spread was only slowed down temporarily. Additionally, the fire burning below ground made containment more difficult since the fire could re-surface when conditions became hotter, drier, and windier, sometimes resulting in a re-burn of a portion of the fire area.
Fortunately, for our crew, we had met with the MDNR earlier this year to talk about planning and prevention efforts in this exact area, including some draft maps and site inspections. These discussions helped us in understanding the containment effort. This wildfire definitely calls attention to the benefits of understanding and working with fire to positively restore and maintain the fire regime in fire-dependent places.
