Year of Award


Document Type


Degree Type

Master of Science (MS)

Degree Name


Department or School/College

College of Forestry and Conservation

Committee Chair

Ronald H. Wakimoto


Forest fires Effect of roads on, Forest fires Montana Bitterroot River Valley


University of Montana


This study evaluated the road effects on fire severity using road density. A fire severity grid dataset created using the Normalized Bum Ratio (NBR) method, fire perimeter created using ground surveys and road density grid data were used to examine the relationship between road density and fire severity. Road density was classified into 12 classes using equal intervals of 1 miles/mile2, and fire severity was classified into four classes (unbumed, low, moderate, and high). Topographic variables (slope, aspect, and cover type) comprising 324,066 acres of the study area were evaluated to correlate their effects on the fire severity of the 2000 fires in the Bitterroot Valley, Montana.

Based on this analysis, it was found that the acreage burned calculated using the fire perimeters was different than using the fire severity calculation. The ground survey fire perimeter overestimated nearly 34% of the study area burned. There was a pattern regarding which types of vegetation burned more severely than others. Lodgepole pine (Pinus contorta) and Douglas-fir/logdepole pine (Pseudotsuga menziesii/Pinus contorta) cover types were found to generate high fire severity. Other cover types did not show consistent effects on severity. The effects of topographic variables (aspect and slope) on fire severity varied within the sites and wilderness and roadless areas in the study area. Some road density classes were concentrated in certain areas of the study area. Therefore, the acreage within a road density class was not consistent across classes.

There was a relationship between road density and fire severity. Fire severity showed a trend throughout different road densities. Initially, high and moderate severities decreased as road density increased, but then they increased again in the higher road density classes. In contrast, low severity increased as road density increased, but it decreased gradually in the higher road density classes. But the causes of these trends were not clear due to the large acreage of the study area. The present of roads has positive and negative effects on fire severity, but such effects were inconsistent. South and west facing aspects were shown to bum less severely. The area in moderate slope classes (11 - 45%) bumed more severely than on the “steep” (>60%) slope class. Removal of the “edge” effects that occurred inside the edge of the ground survey fire perimeter did not significantly change the relationship of fire severity to the road density.



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