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2-1-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Unit 2
2-2-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Unit 2 Objectives
1. Identify standard features on a topographic map.
2. Describe how topography affects fuels and their availability for combustion.
3. Describe how topography can affect the direction and rate of spread of wildland fires.
2-3-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
4. Describe how changes in fuel and topography can provide full and partial barriers to the spread of wildland fires.
5. Describe how slope percent can be determined or estimated in the field.
Unit 2 Objectives
2-4-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
.A
B.
C.
.D
.E
.F .G
H.
I..J
2-4-S290-EP
2-5-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Match these features to the boxes on map:
Contour Line
Elevation
East Aspect
North Aspect
South Aspect
West Aspect
Canyon
Barrier
Box Canyon
Mountain Peak
Intersecting Drainage
Ridge
Topographic Map Features
2-5-S290-EP
2-6-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Topographic Map Features
2-6-S290-EP
2-7-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
How Topography Affects Fuels and Their Availability
for Combustion
2-8-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Elevation Above Sea Level
sea level
grass
shrub
timber
tundra
snow 10,000 ft.
2-8-S290-EP
2-9-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Fires on slope reaching 10 acres +
Pe
rce
nt
of
fire
s
Level Base ofslope
Middle of slope
Top ofslope
2-9-S290-EP
2-10-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Fires starting
at base of
slope often
become the
largest fires.
55%slope
30%slope
0-5%slope
2-11-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Cardinal Directions
• North• South• East
• West
• Northeast
• Northwest• Southeast• Southwest
2-12-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Fire Occurrence by AspectP
erc
ent
of
fire
s
Aspect2-12-S290-EP
2-13-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Effect of Aspect on Fuel Temperature and Moisture
Highest Fuel Moisture
Lowest Average Temperature
Lowest Rate of Spread
Later Curing of Fuels
Late Snow Melt
Earlier Heating
Earlier Cooling
Later Heating
Later Cooling
Lowest Fuel Moisture
Highest Average Temperature
Highest Rate of Spread
Earlier Curing of Fuels
Earlier Snow Melt
2-14-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Aspect Affects Fuel Moisture
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
1 3 5 7 9 11 13 15 17 19 21 23
Time (Military)
% M
oist
ure
Cont
ent
North Slope
South Slope
2-15-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior 2-15-S290-EP
2-16-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
How Topography Can Affect the Direction and Rate of Spread of Wildland Fires
2-16-S290-EP
2-17-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Slope affects fire behavior
Fresh air
Burning chunksRolling down slope
Faster ignition and spread
draft
preheating
2-17-S290-EP
2-18-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior 2-18-S290-EP
2-19-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Wedge shape fire pattern
2-19-S290-EP
2-20-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Wedge Shape
2-20-S290-EP
2-21-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Slope Reversal
2-22-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Slope Reversal
2-22-S290-EP
2-23-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior 2-23-S290-EP
2-24-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Slope Reversal
2-24-S290-EP
2-25-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior 2-25-S290-EP
2-26-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Ridges
2-26-S290-EP
2-27-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior 2-27-S290-EP
2-28-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Fires in the bottom of narrow canyons
2-28-S290-EP
2-29-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Bottom of a narrow canyon
2-30-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Stable Air Conditions
Narrow canyons easily allow for stable air mass, such as an
inversion to form.
2-31-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior 2-31-S290-EP
2-32-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Air flow
Surface winds will usually be shaped by the canyon, following the canyon’s direction, forming
eddies and strong upslope currents at its sharp bends.
2-33-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Intersecting Drainages
2-33-S290-EP
2-34-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Intersecting Drainages
2-34-S290-EP
2-35-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Chimney Effect
2-36-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Chimney Effect Conditions
• Unstable air conditions causing a convection current through the canyon.
• Air drawn in at the base to support convection currents.
• Available fuel to support rapid burnout.
2-37-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
How Changes in Fuel and Topography Can Provide Full and Partial Barriers to the Spread of
Wildland Fires
2-37-S290-EP
2-38-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Barrier Definition
• Barriers are natural or artificial.
• Limit the direction of spread.
• Can provide opportunities for control.
• Barriers may not reduce spotting potential.
A barrier is any obstruction to the spread of fire. Typically an area or strip devoid of combustible fuel.
2-39-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Barriers to Fire Spread
2-40-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Partial Barriers
A change in fuel conditions may offer only a partial barrier by
slowing the spread of fire.
2-41-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Exercise #2
2-42-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Is this a good barrier to fire spread?
2-42-S290-EP
2-43-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Is this a good barrier to fire spread?
2-43-S290-EP
2-44-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Is this a good barrier to fire spread?
2-44-S290-EP
2-45-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Is this a good barrier to fire spread?
2-45-S290-EP
2-46-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Is this a good barrier to fire spread?
2-46-S290-EP
2-47-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Is this a good barrier to fire spread?
2-47-S290-EP
2-48-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
How Slope Percent Can Be Determined or Estimated in the Field
2-48-S290-EP
2-49-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
% Slope vs. Degrees
Percent slope = RiseRun
1 foot
1 fo
ot45
o
100%
X 100
RUN
RIS
E
2-50-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Slope Meter
2-51-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Review Unit 2 Objectives
1. Identify standard features on a topographic map.
2. Describe how topography affects fuels and their availability for combustion.
3. Describe how topography can affect the direction and rate of spread of wildland fires.
2-52-S290-EPUnit 2 Topographic Influences on Wildland Fire Behavior
Review Unit 2 Objectives
4. Describe how changes in fuel and topography can provide full and partial barriers to the spread of wildland fires.
5. Describe how slope percent can be determined or estimated in the field.
