In 2013, SIG completed a fire hazard and risk assessment for the entire Lake Tahoe Basin, with an analysis focused on potential fire behavior in Stream Environment Zones (SEZs) and the wildland urban interface (WUI).
To do this analysis, FAO-AF focused on five questions: 1) How did current anti-wildfire treatments in the Lake Tahoe Basin compare to treatments planned for the next decade; 2) How did fire affect WUI areas and SEZs historically; 3) Given the status of the WUI, SEZs, and fuel treatments at the time, what
was the potential for hazardous fires to incur (based on models of crown fire initiation and conditional burn probability) in the WUI and SEZ areas of the Lake Tahoe Basin; 4) How do WUI, SEZs, and fuel treatments differ between hardwood dominated riparian systems, or within annual or perennial systems at different reaches of the watershed; and 5) How would implementing the planned treatments change the potential for fire initiation and burn probability in the WUI and SEZs of the Lake Tahoe Basin?
The project covered all lands within the Lake Tahoe Basin Management Unit, which included a 231,285 acre LiDAR sample area. The general approach was to develop fire behavior and probability inputs within the Lake Tahoe Basin using LiDAR, WorldView-2 imagery and existing GIS layers.
Findings showed that, as with much of the Sierra Nevada Range, fire was common in the Lake Tahoe Basin prior to the late 19th and early 20th centuries. In the latter half of the 20th century, fires were also relatively consistent in number per year, but vast majority of the fires were controlled before they grew to an acre or more in size, resulting to a near absence of fire on the landscape over this period of time. Existing current policies focused on fire exclusion, as well as the difficulties with doing large scale prescribed burning have essentially removed fire as an ecosystem process at a landscape scale from the Lake Tahoe Basin over the past nearly 100 years. However, areas that did receive fire treatments within the WUI, riparian vegetation, or outside of these areas consistently had a lower probability for passive or active fires; treatments more than 15 years old also had a lower potential for passive or active crown fire when compared with areas that were not treated at all. The report concluded that continued, incorporation of knowledge from fire managers and others with: local fire experience, WUI protection experience, skills in evacuation procedures, and understanding of local ecological conditions is critical to the continued long term planning and success of any fuel management strategy.