Anchorage reducing wildfire risk with Remote Sensing

Anchorage reducing wildfire risk with Remote Sensing

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Alaska, the 49th state to join the Union, is known for its picturesque landscapes, pristine bodies of water and abundant wildlife. What isn’t widely known is that over the last few years, insects less than one-fourth inch aggressively were wiping out spruce trees in Anchorage, Alaska, USA. The spruce bark beetle infestation on Anchorage’s wildlands left over 85,000 acres of dry, rotted, forestland in its wake, creating a major wildfire threat. This threat resulted in the Municipality of Anchorage (MOA) being named a community at risk by the USDA Forest Service in 2001; and prompted the Municipality to take action to reduce its wildfire risk using remote sensing technology. The Wildfire Mitigation Project became a collaborative effort between the MOA’s Data/GIS Resources Division, Anchorage Fire Department, Alaska Department of Natural Resources (DNR) Division of Forestry, Bureau of Land Management (BLM), Anchorage Soil and Water Conservation District (ASWCD) and the University of Alaska Anchorage. The Municipality contracted IGIS Technologies (IGIST), Inc. (San Diego, Calif., USA), a GPS, GIS and remote sensing solutions company, to achieve the following objectives: assess the forest fuel structure in Anchorage’s wildland/urban interface areas; develop predictive fire behavior models; and assess wildfire risks.

IGIST created a landcover map and fire hazard map of the wildland/urban interface around Anchorage. Using IMAGINE Professional V8.5, IGIST ran an unsupervised classification on a Landsat TM image of Anchorage taken in 2000. Forestry inventory labels were determined using data from multiple resolutions, including: one-meter aerial photos, 4-meter IKONOS, 50-meter USGS landcover, and GPS transects adjacent to the classified imagery. The classified imagery was used as the central component in creating a spatial model to determine fire hazard. In conjunction with the MOA, Department of Natural Resources (DNR), and the Anchorage Fire Department, IGIST created a spatial model that consisted of seven key inputs:

  • Vegetation classification
  • Slope
  • Aspect
  • Beetle spruce kill areas
  • Distance to roads
  • Distance to nearest water source
  • Population density

    These inputs were combined within the IMAGINE Spatial Modeler. The final output ranked each class with numerical weights that related to fire risk level.
    For example, if an infested area is close to a water source, it was given a low fire risk weight, and if the area is far away from water, it was given a larger weight, meaning that area has a moderate-to-high fire risk.

    The DNR Division of Forestry combined land cover layers with FARSITE, a GIS-based program that simulates growth and fire behavior of fires as they spread through different terrain under changing weather conditions.

    Vegetation layers were incorporated into FARSITE and the results were converted into fuel models. (Fuels include grass, shrub or timber that escalate the threat of wildfire.) Analysts are manipulating and analyzing the classification process to help develop custom fire behavior models that best represent forestland conditions in Anchorage. This will be an ongoing process as better imagery and data is obtained and forestland conditions change. The MOA will continue to obtain better images and data over the years, as forestland conditions will continue changing over time. The steps of this project will be repeated to ensure the Municipality has the most up-to-date information needed to minimize wildfire threat to human life, property and natural resources. This project demonstrates how Anchorage is successfully combining GIS software and procedures with effective firefighting policies. The MOA now has the information and guidelines needed to improve forest health management, pinpoint wildfire risk hazards and keep the public informed.