S-190: Module 2 - Principles of Wildland fire Behavior 2024 Questions And Revised Correct Answers Local topography effects a fire's, (blank), & (blank). - Answer - Intensity, and, Rate/Direction of Spread. A slopes, (BLANK), is the compass direction the slope faces. - Answer - Aspect The, (blank), of a slope determines the effect of the sun's heat on the slope's plants & trees, air temperature, & moisture retention of the soil. - Answer - Aspect Solar, (blank), heating can influence fire behavior by influencing fuel moisture and ignition points. - Answer - Radiant Heating A, (blank), facing slope tends to have heavier fuels, lower temperatures, higher humidity, & higher fuel moisture, than a, (blank), facing slope. - Answer - North, South In the Northern Hemisphere, the slopes facing , (blank), receive direct sun rays & become hotter than the slopes facing any other direction. - Answer - South In the absence of winds, fire usually moves, (blank), uphill than downhill. - Answer - Faster. So the steeper the slope, the faster a fire move s. Why is the rate of spread (ROS) increased for upslope fires? - Answer - Because: 1. The flames are closer to fuel sources. 2. Wind currents typically move uphill during the day, pushing heat to new fuel sources. 3. Upslope fires create a draft, increas ing the ROS. Wildland fires tend to burn much faster upslope than on level ground because of, (BLANK). - Answer - Preheated fuels When you have a fire at the top of a slope, building a, (blank), just beyond a ridge will help you contain the advancing fir e. - Answer - Fireline Slope is measure in, (blank over blank), which is expressed as a percentage. - Answer - Rise over Run Example: A rise of 25 feet divided by a horizontal distance of 100 feet & then multiplied by 100 represents a 25 percent slope. Upslope fires can cause, (blank), to roll downhill. - Answer - Burning Debris What is a "chute"? - Answer - A chute is a steep v -shaped drainage on a slope which can easily channel smoke and fire upward at a rapid rate. What is a "saddle"? - Answer - A saddle is a common name for a depression between two adjacent hilltops. Why are "chutes" & "saddles" so dangerous? - Answer - 1. They drastically accelerate fires. 2. They alter the flow of winds causing erratic fire behavior. 3. They change the rate and d irection of spread by acting like chimneys & literally propel the fire up as if through a stove pipe. Wind channeling is, (blank). - Answer - Is a direct result of natural features like chutes & saddles. What are the three different types of canyons? - Answer - 1. Box canyons 2. Narrow canyons, & 3. Wide canyons What is a Box Canyon's specific effect on fire? - Answer - The creation of strong upslope drafts results in extreme fire behavior. What is a Narrow Canyon's specific effect on fire? - Answer - Fire can easily spread fuels on the opposite side by radiation and spotting. What is a Wide Canyon's specific effect on fire? - Answer - Cross -canyon spotting of fires is not common except in high winds. Fires starting near the base of box canyons & narro w canyons may react similar to, (blank). - Answer - Similar to a fire in a wood burning stove or fireplace. Air will be drawn in from the canyon bottom creating very strong upslope drafts.These upslope drafts create what is called the "chimney effect". As air drops in elevation the atmospheric pressure, (blank). - Answer - Increases. This causes the air to compress and heat. The resulting winds can create poor conditions for wildland fire control. (Blank), winds are the result from air being forced over m ountain ridges by convection or high barometric pressure. - Answer - Gravity Winds Because of high temperatures, fuels as, (blank), elevations, dry out earlier in the year than those at, (blank), elevations. - Answer - lower elevations, higher elevations There are typically less fuel loads at, (blank), elevations. - Answer - higher elevations
