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CFFDRS System Overview

Introduction

The Canadian Forest Fire Danger Rating System, as shown in these flow charts, is designed as a comprehensive system of tools designed to evaluate environmental factors that influence the ignition, spread, and behavior of wildland fire.

CFFDRS Components

The system had its origins from early efforts dating to the 1920's and the developmet of the "tracer index", a forerunner of the Fine Fuel Moisture Code (FFMC).
CFFDRS Components

Fire Weather Index (FWI) System Process Flow Chart

The FWI system was developed and introduced across Canada in 1970.  Due to its simplicity in terms of data required and outputs produced, it is used both globally and within many regions around the world.
FWI Process Flow Chart

Fire Behavior Prediction (FBP) System Process Flow Chart

The FBP system tools were released in interim form in1984, with more formal introduction in 1992 and revisions in 2008.
FBP Process Flow Chart
Additional systems for fuel moisture (e.g. hourly FFMC and Grass Fuel Moisture) and ignition have followed. 

There are several important Distinctions for NFDRS and NFBPS Users.

Use of English Units

All the CFFDRS tools and references produced by the Canadian and Provincial governments, as well as applications produced internationally, use the metric system for all measured values.  For the most part, measures referenced here are in English units to facilitate utility and use in the United States.

Wind Observations

This table provides a quick reference to aid conversion between 10m, 20ft, unsheltered Eye Level (EL Op) observations, and Forecast/Airport winds. 

CFFDRS Weather observations, provided to the system for both FWI and FBP calculations, generally conform to familiar fire weather standards. These standards can be reviewed in the weather guide found in Reference Section. However, wind observation standards conform to the international 10m height as opposed to the NFDRS 20ft height standard.

Wind Sensor Standard
(Andrews, 2012)

CFFDRS models and tools do not expressly apply relationships between the standard 10m wind measurements and others that US users may be familiar with.  Both 20ft and eye level winds are commonly referenced and reported from US RAWS observing locations and from the fireline. 

Further, windspeeds reported from Airport (ASOS) and provided in NWS weather forecasts generally report higher windspeed, where surrounding terrain is flat with little variation in vegetation height or structural interference and is highly correlated with forecast windspeed provided in the National Digital Forecast Database (Lawson and Armitage, 2008).

(Lawson & Armitage, 2008)

Fire Intensity Measures

A major adaptation in US tools and references (with uncertain validity) is the use of flame length for fire intensity outputs in the fire behavior tables. FBP outputs (kW/m) were converted to BTU/ft/sec using standard conversions and then to flame length using the formula


This table identifies the CFFBP Fire Intensity thresholds in kW/m and the corresponding values in english units (BTU/ft/sec) and flame length in feet. These thresholds are consistent with commonly held flame length thresholds for fire safety interpretations in the US system.