5m ago

36 Views

0 Downloads

282.01 KB

12 Pages

Transcription

Intermediate Wildland Fire Behavior, S-290Pre-Course WorkThe pre-course work is designed to ensure that students come to class with a basicunderstanding of the fire environment in order to learn Intermediate Fire Behaviorconcepts.The pre-course work is divided into seven parts that correspond to questions on thepre-qualifying test. Complete the pre-qualifying test using the information on theStudent CD.When you have completed the pre-qualifying test, mail it back to the coursecoordinator in the provided envelope. You must receive a passing score of 70% orhigher to be considered for admittance to the course.

Part 1 – Basic Firefighter MathObjective: Define and apply the concept of ratios and percentages.A ratio is a proportional relationship of one value to another such as the ratio ofgas to oil in a chain saw fuel mix. Ratios can be written as a fraction (½) or inratio notation (1:2). The value of a ratio is the division of the first number by thesecond number.Example: A chain saw manufacturer specifies that the proper fuel mix is 32:1,which means, one unit of 2-cycle oil is added to 32 units of gas.Ever hear the phrase, “Do not exceed a two to one (2:1) work/rest ratio?” Thismeans for every two hours worked, one hour of rest (or off-shift time) is provided.If you work a 16 hour shift, how many hours of rest are you supposed to have?Answer: 16 hrs worked, 24 hours available in a day.24 hours – 16 hrs 8 hrs of rest time available.Does this meet the 2:1 ratio?By applying work hours to rest hours as a ratio:16 hrs/8 hrs is the ratio, and by simplifying (dividing each by 8) we get 2/1 or 2:1,or 2x.Note that 2x indicates a two-fold increase, or two times the original value. Thismakes it easier to visualize in the fire environment.As part of a map scale, a representative fraction is also a ratio. Common 7.5minute topography maps have a representative fraction of 1:24,000, which meansevery 1 unit of map distance is equal to (represents) 24,000 units of actual grounddistance. Note that a common unit of measure when working with representativefractions is inches.

A percent compares things to one another, or the amount less than or greater thana common base of 100 (70 right answers out of 100 possible 0.7 or 70%). Wethen relate this percentage to some threshold or relevant value to give meaning.For example, we know that a 10% slope is a slight incline, not terribly difficult towalk up. But a 70% slope is steep, requiring much more energy to climb. Todetermine a percent, you divide the ratio fraction and multiply by 100. What is thepercentage if you score 37 correct answers out of a possible 48?Answer: 37/48 .771 x 100 77% (rounded).Slope is expressed as a percentage and determining slope percent is based on a ratioby applying this formula: Slope% rise (in elevation)/run (horizontal distance) x100 between two points. Note that run is always a flat map distance, not theincline distance you would walk from one point to another.Given a rise of 500 feet in elevation and a horizontal distance between two pointsof 1200 feet, we plug these numbers into the equation and can determine slope %.Answer: 500 feet rise/1200 feet run .416 x 100 42% (rounded).To test your understanding, answer the questions under Part 2 of the pre-qualifyingtest.

Part 2 - MapsPart 3 contains excerpts from the Map and Compass publication located on theStudent CD.Objectives: Identify important elements found on a map legend.Identify features commonly found on topographic maps.Determine aspect from a topographic map.A map is designed for the purpose of permitting you to visualize a portion of theearth's surface, drawn to a specified scale, with pertinent features properlypositioned to facilitate planning and organizing operations. Maps, although drawnto a scale, are not absolutely accurate because they represent a curved and unevensurface on a flat piece of paper. Furthermore, photocopying, scanning, or othergraphic reproductions can further skew a map. Care must be taken to ensure thatthe map you are using reflects true map distance to ground distance measurements.There are three basic types of maps:1.Planimetric MapsPlanimetric maps show the positions of features without showing theirrelationship to the hills and valleys of the land. They can include rivers,lakes, roads, boundaries, or other human-made, symbolic features. Forexample:a.Common road mapsRoad atlas, street maps, and Thomas Guides.b.Specific area mapsPreplan maps, floor plan maps, storm drain, sewer and water systemmaps.c.Schematic mapsAgency maps (unit, aviation, resource, district response maps).

2.Topographic MapsTopographic maps show both the horizontal and vertical (relief) positions offeatures. Topographic maps are often referred to as quadrangles or quads,for example:a.Contour mapsThese are the most common method of representing the shape andelevation of the land. A contour is a line of equal elevation on theground that delineates the same elevation above or below a specificreference elevation, usually sea level.b.Shaded-relief mapsThese are pictorial. They are shaded to simulate sunlight on theterrain. This shadow effect accentuates the shape of the physicalfeatures.For fire behavior purposes, we generally work with topographic maps.3.Orthophoto MapsOrthophoto maps depict terrain and other features by color-enhancedphotographic images. It is an aerial photograph of the land.Some orthophoto maps are overlain with contour lines and other featurescommonly associated with topographic maps. These maps are corrected forscale and are the same size as U.S.G.S. quads.

Key map parts:Map Legend: A legend shows information needed to interpret a map. Each typeof map has information represented in a different way relating to its subject matter.The legend can explain map scales, symbols, and color.Map Scale: The map scale indicates the ratio or proportion of the horizontaldistance on the map to the corresponding horizontal distance on the ground.Representative Fraction (R.F.) Scale: Expresses the ratio of the map distance to theground distance in like units of measurements. It is usually written as a fraction orratio. A representative fraction is always written with the map distance as one. Arepresentative fraction of 1/24,000 (1:24,000) means that one UNIT ofmeasurement (inches, millimeters, feet, etc.) on the map is equal to 24,000 of theSAME UNITS on the ground. You CANNOT mix units in a representativefraction. If it is one INCH on the map, it is 24,000 INCHES on the ground.Graphic scale (G.S.) or Comparison Scale: This is entirely different. It usuallyCOMPARES map distances to the ground distance in DIFFERENT units ofmeasurements. Usually a graphic scale is a line marked off on a map indicating somany inches or millimeters equal so many feet, kilometers, chains, or miles on theground. A comparison scale of 1" to 2000 feet means that 1 inch on the map isproportioned to 2000 feet on the ground. We are comparing inches and feet whichare DIFFERENT UNITS of measurement.Table 9, found in the Fire Behavior Appendix B is a useful tool to easily see mapscale conversion factors of various representative fractions.Contour Lines: A contour line is a line on a map or chart connecting all points ofthe same elevation. Any point on a contour line is the same elevation as all theother points on the same line. In other words, contour lines connect points of equalelevation.Contour Interval: This is the difference in elevation between two adjacent contourlines. On U.S.G.S. maps they could be drawn at any elevation, but in practice theyare drawn at intervals of 1, 5, 10, 20, 40, and 80 feet. Occasionally you will find amap with a 25 foot contour interval or metric units, but not often.

Index Contour: To make the contours easier to read, every fifth one is printeddarker and has the elevation marked every so often in the line. The thinner orlighter colored contour lines are called intermediate contours.Contours have certain general characteristics. Following are characteristics whichare not rules but guidelines that are helpful in many cases. Usually have smooth curves. Exceptions are large outcrops of rocks, cliffs,and fractured areas of the earth's surface. Are "V" shaped in stream beds and narrow valleys. The point of the "V"always points uphill or upstream. Are usually "U" shaped on ridges with the "U" bottom pointing down theridge. Are usually "M" or "W" shaped just upstream from stream junctions. Tend to run perpendicular to streams. Tend to parallel each other, each approximately the shape of the one above itand the one below it. Do not cross or touch. Exception is overhanging cliffs. Do not fork. Never end on the map, only at the map edges and sometimes at overhangingcliffs. Indicate steep terrain by being closely spaced. Indicate a uniform slope by being equally spaced. Indicate depressions or pit by a hachured (short lines extending from thecontour line at right angles) contour line joined forming a circle. Indicate elevation in feet above mean sea level in index contours.

Contour characteristic terminology: Depression: A low place in the ground having no outlet for surfacedrainage. Hill: Naturally occurring mass of earth whose crest or summit is at a lowerelevation than a mountain. Mesa: A flat-topped mountain bounded on all sides by steep terrain. Ridge: Long narrow elevation of land, often located on a mountainside. Saddle: Ridge between two hills or summits. Valley: Stretch of low land lying between hills or mountains and sometimesoccupied by a stream. Slope: An inclined ground surface that forms an angle with the horizontalplane (flat ground). The degree of inclination, steepness, is also calledslope. Aspect: The compass direction that a slope faces. By visualizing thecontours on a topographic map, aspect can be determined even though themap is a flat surface. Widely spaced contours indicate a gentle slope,probably not a well defined aspect. But contours closely spaced indicatesteep terrain and aspect can easily be determined.To test your understanding, answer the questions under Part 3 of the pre-qualifyingtest.

Part 3 – Fire Environment VisualizationObjective: Identify common visual indicators used to estimate size and distance,and be able to relate to fire spread rate and flame lengths.Determining distances from known points on a map is rather simple. But whenyou are in the field, it is another matter, unless you can relate to something known.How long are those flame lengths? Or how fast is this fire spreading? Obviouslydirect measurement is the most accurate way to make determinations. But how doyou physically measure flame length on a high intensity fire? Is it important toknow spread distance in feet or chains per hour? Using references in the field(something of known length or size) are very good aids to make calculatedestimates of fire behavior. Learn to visualize the fire environment.Visualization tools: What is the average canopy height of the trees? Telephonepoles are about 30 feet tall. Fence posts are about 5 feet tall. How tall is the brushor grass you are standing next to, which is also the same fuel the fire is consuming?By relating flame length to the height of a known object, you can come up with aratio to estimate. Example: Trees in the area are 40 feet tall. Flame lengths areone-half the height of the trees. Average flame length is about 20 feet (.5x theheight of the trees in this example).An effective way to estimate rate of spread is to know how much time it takes toburn between two known points. To determine spread distance, measure thedistance between two points. Start timing when fire reaches the first point, andstop timing when fire reaches the second point. This establishes a ratio, whichthen can be mathematically applied to a unit of measure and time (ft/min,chains/hour, or miles/hour).Other aids include using the odometer in a vehicle or by pacing to establish knownground distance. Range finders are useful if you have one. Barbed wire fenceposts are about 1 rod (16.5 feet) apart. The distance between 4 fence posts then is1 chain (66 feet). Although more variable, the distance between telephone poles isabout 132 feet. On a larger scale and using a map, you can relate terrain features todistance and get a good idea of how quickly a fire is advancing.

Another hint: Most detection reports list a time of discovery. By estimating howfar the fire has traveled upon your arrival and noting your arrival time, you candetermine fire spread. But a word of caution: the fire environment is dynamic(changing with time and space). What occurred in the past may be of value, butmay not apply to the current situation or what could happen in the near future. Forsafety reasons, base all your actions on current conditions, the forecasted expectedconditions, and what the fire is doing (fire behavior).Awareness and relationships tend to be more important than actual measurements.In this course you are going to learn more about fire events which don’t require alot of math or figuring. When is the next “Big Change” coming? Is it very little,such as a 2-fold (2x) increase, or is it a big change, such as a 60-fold (60x) change?When the change happens, are fire fighters at risk? Is there enough time to get to asafety zone when the change comes? Understanding the fire environment alongwith the magnitude of the “big change” is the key.To test your understanding, answer the questions under Part 4 of the pre-qualifyingtest.

Part 4 – Basic Principles of Fire BehaviorObjective: Understand basic fire behavior principles presented in S-190,Introduction to Fire Behavior.To test your understanding, answer the questions under Part 5 of the pre-qualifyingtest.Part 5 – Fuel Groups/ModelsObjective: Introduce student to fire behavior fuel groups and general fuel modelcharacteristics within each fuel group.Review the article, “Aid for Determining Fuel Models for Estimating Fir