Rio Hondo Assemblages 2018

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Sandiegouniontribune.com, 13 Aug. 2017

Leonard, Jack. “Night of the Cedar Fire.” Los Angeles Times. 28 Dec. 2003.

“The 2003 San Diego County Fire Siege Fire Safety Review.” USDA forest service, 2003.

Wilkens, John. “Remembering Cedar Fire's Deadliest Surge.” Sandiegouniontribune.com,
19 Oct. 2013

Mann Gulch Fire
by William Taylor

There are a handful wild land fires that are so infamous that they are discussed to
all those working in the wild land fire service. Of those, there is one named The Mann
Gulch Fire that is especially tragic and well known due to the death of 13 heroes and the
lessons learned from their fate. There are many factors that exacerbated the fire behavior
that led to that terrible day on August 5th, 1949. There was the topography of the area, the
weather, the fuels that fed the fire, and the sudden shift in wind. All these factors created
a domino effect and changed the fire situation from what they deemed as, “not bad” to
the race for their lives (Board of Report of Review 1949).

Knowing the fuels in the area is the first step into understanding how the fire
behavior became so extreme so quickly. The fuels in the area were especially dangerous
for multiple reasons. According to Richard C. Rothermel, who wrote Mann Gulch: The
Race That Couldn’t Be Won:

Vegetation on the north side of Mann Gulch was mature 60- to more than 100-yr-
old ponderosa pine. The south side was covered with 15- to 50-yr-old Douglas-fir,
mixed with mature ponderosa pine and some mature juniper. Fronting the river
was a stand of 60- to more than 80-yr-old Douglas-fir. Mixed pine and fir grew in
the bottom of the gulch. A distinct moisture gradient is evident in the gulch; the
lower slopes receive more moisture than the upper slopes. This influences the
vegetation found in the understory beneath the forest canopy. At the time of the
fire, lower elevations had heavier undergrowth, which gave way to scattered
timber and grass in the drier areas farther up the gulch. The fire at this stage was

burning in a stand of much denser forest than they were in farther up the gulch.
Fuels in the area where the spot fires started were estimated to have been timber
litter and live understory vegetation interspersed with accumulations of heavy
dead and down woody material. (Rothermel 1993)

As reported in the Report of Board of Review, the predominant surface fuel was
bunchgrass and cheatgrass. (6) “The survivors reported they traveled through tall grass
much of the time. Grass would have been fully cured (dried out) by August 5 at this low
elevation (3,600 ft). The moisture content of fine dead fuels during the hottest part of the
day was calculated from the temperature and humidity to have been about 3.5 percent”
(Rothermel 1993). Knowing the various fuel types where the spot fire began gives insight
into the first piece of the puzzle and can continue to piece together why the fire behavior
blew out of control.

The topography of the area can only be described as hazardous when it comes to
weather and fire behavior. First, the slope of the land aggravated the fire behavior
because of the steepness of the slope ranging from 18 to around 44 percent, and distance
between the adjacent slopes (Rothermel 1993). The steep slopes enabled heat convection
from the fire to preheat the fuels above it. What little moisture was left in the live fuel
was quickly removed making the fuel burn more intensely and further speeding the rate
of spread. A second way the topography of the land affected the fire behavior was how
close the adjacent slope was. Firebrands from the main fire were carried by the winds to
the north slope ahead of the crew. Last, there is the overall shape of the gulch and how it
helped drive the fire once the winds shifted. “Mann Gulch is a minor drainage, leading
into the Missouri River from the east. It is funnel shaped, narrowing to a width of one-

fourth mile at the river. The highest flanking ridge, where the fire started, is on the south
side of the drainage between Mann Gulch and Meriwether Canyon” (Rothermel 1993).
The shape of the gulch is perfect for funneling wind if it were to blow in from the West
or South West. “Because of the orientation of the canyons and ridges, a strong southerly
wind would create extreme turbulence at the mouth of Mann Gulch, producing strong
winds that would blow up the gulch” (Rothermel 1993) The wind would find the path of
least resistance and flow right through the gulch, pushing and fueling the fire causing it to
burn hotter and spread faster.

Another factor that also led to the intense fire behavior was the weather, not just
the day of the tragedy, but also the days and months previous. According to the Report of
Board of Review, the weather taken that day at 1700 was said to be 97 degrees
Fahrenheit, 22 percent humidity, and fuel moisture level was at 5.9 percent, with winds
blowing at 16 miles per hour setting the burning index to 74. Obviously, these are perfect
weather conditions for a fire to burn, but what set the conditions for disaster were the
conditions the day before.

Also, stated in the Report was that on the day the fire started the fire danger was
only 16, which indicates a very low rate of spread potential. This could have led the crew
to become a little more relaxed and allowed them to be caught off guard by the fires
sudden run through the gulch. “Survivors Sallee and Rumsey both said the crew was not
worried about safety” (Rothermel 1993). Of course, being able to predict such a radical
change in wind direction, especially in that date and time, would be unlikely, but the crew
knew the dangers of their location when they were hiking towards the river. “Sallee

thought he heard Dodge say some-thing about the thicket of ponderosa pine and Douglas-
fir they were in being a death trap” (Rothermel 1993).

The conditions for burning were there, but the wind was blowing from the north,
forcing the fire to burn slowly towards the north east according to the weather taken in
Helena early in the day. The greatest weather influence that ignited the rapid increase in
fire behavior was the sudden shift in wind direction. Coupled with the topography of the
gulch that funneled the wind the events of the day would take a sudden change for the
worse. “Dodge had a clear view of the fire and could see it was burning more rapidly than
before. In Helena, the wind had been blowing from the north and east at 6 to 8 mi/h that
afternoon. At 3:30 p.m. the wind switched to the south, increased to 24 mi/h, and
continued to blow strongly from the south at 14 to 22 mi/h. Because of the orientation of
the canyons and ridges, a strong southerly wind would create extreme turbulence at the
mouth of Mann Gulch, producing strong winds that would blow up the gulch toward the
crew” (Rothermel 1993).

At the site of the spot fire there were heavier surface fuels that led to dispersed
trees and tall grass in the drier areas farther up the gulch where the crew was. The slope
would allow for preheating and the fire would have become more intense to where the
flames were extending up into the tree crowns. The strong gusty winds would have
pushed the fire through the crowns directly towards Dodge and his crew” (Rothermel
1993) At this point Dodge realized he and his crew needed to escape and headed
North/East and eventually told them to drop their gear to lighten their load. Once the
wind was aligned with the gulch, the perfect fire storm was created. With the exception

of the three sole survivors, the crew entered a race for their lives, A Race That Could Not
Be Won.

Bibliography
Rothermel, Richard C. “Mann Gulch Fire: A Race That Couldnt Be Won.” 1993,

doi:10.2737/int-gtr-299.

United States Congress, “Report of Board of Review: Mann Gulch Fire, Helena National
Forest – August 5, 1949.” Report of Board of Review: Mann Gulch Fire, Helena
National Forest, 1949.