Lab 3 Willow Fire Analysis

1999 Willow Fire Analysis

The 1999 Willow Fire in San Bernardino County, California, was one of the worst forest fires in recent history. The fire began on August 28, 1999, approximately 90 miles east of Los Angeles near Lake Arrowhead. The fire lasted seven days and burned approximately 68,723.5 acres or approximately 107 square miles of vegetation in the San Bernardino National Forest and private land per the data provided in the map above. This fire threatened the resort towns of Big Bear and Lake Arrowhead. The fire was declared contained on Saturday, September 5, 1999.

The map above illustrates the spatial analysis of burnt vegetation in the 1999 Willow Fire. There are six polygons representing the different types of vegetation within the burn area of the Willow Fire which are as follows:
1. Coastal Scrub – 14% of total area burned in acres
2. Desert Scrub – 26% of total area burned in acres
3. Juniper – 14% of total area burned in acres
4. Montane Harwood-Conifer – 11% of total area burned in acres
5. Pinyon-Juniper – 32% of total area burned in acres
6. Urban Agriculture – 3% of total area burned in acres

This map was created using daily observations and surveys of the area burnt during the Willow Fire. The overlapping areas represent the vegetation that continued to burn between the daily observations. To create a map of the total burn area of the six polygons, the Union and Dissolve functions were utilized in Arc Toolbox. The unit of measurement used for the area of these polygons is meters. The areas/polygons (in meters) were then converted to acres to find the percentage of total area burnt for each vegetation type.

The largest areas burnt, according to the above vegetation analysis, consisted mostly of Pinyon-Juniper and Desert Scrub. Pinyon-Juniper vegetation is generally found in the western United States between 5,000 and 7,000 feet. This vegetation has evolved to be resistant to cold weather and drought. It is usually found bordering Desert Scrub and Montane Forests in higher elevations. (spuds.agron.ksu.edu/Pj.htm)

High winds, low humidity, and arid vegetation combined to make this a devastating fire. Wind created by the high temperature fire may have caused one vegetation type to burn more than another. Fire usually follows the path of least moisture; in this case it would burn across the Desert Scrub. Some species of vegetation, such as Montane Hardwood-Conifer and Pinyon-Juniper, necessitate fire to reproduce which allows their seeds to germinate without competition for light and water.

Geographic information system technology helps us understand the spatial characteristics of phenomena. The map above can be used in several different ways:
Ø Fire containment under similar ecotopes (Tansley) and conditions.
Ø Replanting vegetation
Ø Soil rehabilitation according to the vegetation type