Lake e. Case Study: How Fuel Treatment Areas Affect Wildland Urban Interface Fires. Saskatchewan.ca/fire

Transcription

1 Lake e Case Study: How Fuel Treatment Areas Affect Wildland Urban Interface Fires Saskatchewan.ca/fire

2 Acknowledgements The author would like to thank the following individuals for supplying the information that was vital for the completion of this case study: Air Attack Officers Working the Fire: Dan Bast, Eric Braaten, Kevin Frey, for supplying; air tanker drop information, time lines, fire observations, and pictures of the incident. Fire Investigators: Conservation Officers; Ken Ness, Brendon Smith, Evan Maxwell and Al Hrynkiw who provided pictures and fire details for the case study. GIS Specialist: Dana Jones for running the Prometheus fire growth projection and preparing maps suitable for the case study. Prevention & Mitigation Specialists: Camille Harris and Owen Price for providing technical advice and reviewing the document. Meteorologists: Henri Dagenais, Daniel Poirier and James Schofield for providing historical weather and fire indices. i P a g e

3 Contents INTRODUCTION... 1 FIRE CHRONOLOGY AND DEVELOPMENT... 1 DESCRIPTION OF THE FIRE ENVIRONMENT... 6 Fuels... 6 WEATHER... 7 Antecedent Climatic Conditions... 7 Fire Indices... 8 Surface Weather Observations... 8 Topography...14 FIRE BEHAVIOUR...15 Observed Rates of Spread...15 Projected Rates of Spread...15 Fire Behaviour...15 Map of Fire Projection...15 FUEL BREAK AND FIRE INTERACTION...16 CONCLUSION...20 Figure 1 - Picture showing fire origin indicated as a circle and burn patterns showing initial fire runs. Note that roads and trails in this picture were not created as part of suppression effort 2 Figure 2- Picture looking from fire origin to the east toward Black Lake along what used to be the north flank of the fire. Smoke shows 90 degree wind switch from initial run, Camp Grayling was just catching on fire..3 Figure 3 Picture showing Camp Grayling burning as Air Tankers lay down a retardant line along the fire guard between the fire and the community..4 Figure 4 Overview of Blib fire looking in a westerly direction 5 Figure 5 Picture of the upper sized trees that the post cutters were harvesting within the stand where the fire originated.6 Figure 6 Construction of the fire guard at Black Lake in Figure 7 Map of Saskatchewan showing percent normal precipitation for April 1, 2015 to June 15, 2015 compared to stats from The circle at the top indicates Black Lake area..8 Figure 8 18Z (1200 local) surface analysis..11 Figure local surface prognosis May Figure local surface prognosis May Figure 11 12Z (0600 local) May surface analysis..14 ii P a g e

4 Figure 12 - Prometheus wildfire projection showing the projected advancement of the fire from 2100 hrs to 0000 hrs..16 Figure 13 Picture showing burn scar indicating a full crown fire as fire hit the fire guard. Note the retardant line on the community side of the guard and the splash pile in the middle of the guard..17 Figure 14 Close up of fire guard showing some spark Black Spruce and Jack Pine regen coming up on the cleared site Figure 15 Left, an aerial picture of the tanker drops along the community side of the fire guard...19 Figure 16 Picture of the fire approaching the fire guard when the tankers left the fire at 2030 hrs...19 Table 1: Fire Weather Indices for the fire area taken from two nearby weather stations on the day of the fire. Weather readings are noon actuals (Central Standard Time) and are used to forecast for burning conditions at 1600 hrs based on the normal diurnal curve Table 2: Surface Weather Observations from the Stony Rapids Weather Station for May 15th from 1500 hrs 2300 hrs Table 3: Surface Weather Observations from the Beatrice Weather Station for May 15th from 1500 hrs 2300 hrs... 9 Table 4: Hourly FFMC, ISI and FWI from the Beatrice Weather Station for May 15th from 1500 hrs 2300 hrs...10 Table 5: The weather data used to run the Prometheus fire growth projection...15 iii P a g e

5 INTRODUCTION The Blib Fire (Black Lake Indian Band - Blib) was reported on Friday, May 15, The fire s origin was 3.8 km north of the First Nation community of Black Lake in northern Saskatchewan. The fire was responsible for burning out an Outfitting Camp and directly threatened the community of Black Lake, prompting the evacuation of the community. The fire was a one day incident, growing to 668 ha in size, burning 20 structures within the outfitting camp, and coming within 750 m of Black Lake where it stopped when it ran into a fire guard that had been constructed 9 years earlier to protect the community from another wildfire. This case study looks at the fire behaviour in relation to the fuel, weather and topography with a focus on the role the fireguard played in protecting the community from the wildfire. The community of Black Lake is located on the northwest shore of Black Lake in Northern Saskatchewan, 453 km north of the town of La Ronge. FIRE CHRONOLOGY AND DEVELOPMENT The Blib Fire was reported at 1537 hrs Central Standard Time on May 15, 2015 and started at approximately 1515 hrs. The fire was ignited when post cutters left a campfire going while they worked nearby. When they noticed that the campfire had burned out of the fire pit they tried to put it out with some water but were unsuccessful in doing so. Hot, dry, and windy conditions allowed the surface fire to quickly transition into a full crown fire in the dense C 3 1 Jack Pine (Pinus banksiana) stands that dominate this area. Burn patterns indicate that the fire took some significant runs within a short period of time after ignition. 1 Canadian Forest Fire Behaviour Prediction System Fuel Model Type. 1 P a g e

6 Fond du Lac River Old Burn 1 Old Burn 2 Fire Origin Figure 1 - Fire origin indicated as a circle and burn patterns showing initial fire runs. Note that roads and trails in picture were not created as part of suppression effort. By 1637 hrs, the Air Attack Officer working the fire reported that the fire was running in an easterly direction at an intensity class 5 2. The fire was reported to be 150 ha at the time and had already jumped the Fond du Lac River. The southern flank of the fire followed an existing road and an old burn. The northern flank of the fire cut the edge of another old burn along the Fond du Lac River. The old burns acted as a bit of a fuel break, the sparse fuels within the old burns significantly slowed fire spread. The Air Attack Officer provided another report at 1654 hrs. The fire was still burning at an intensity class 5 and had exceeded 200 ha in size. Retardant lines had been dropped to try to protect Camp Grayling. The fire continued to run in an east / southeasterly direction where it jumped onto Fir Island on Black Lake, a distance of over 700 m, see Figure 2. The Fire Weather Forecasters out of the Provincial Fire Centre in Prince Albert forecasted the passing of a cold front that would result in a 90 degree wind switch for the fire and at 1722 hours the ground crews confirmed that the wind had shifted and it was now coming out of the north / northwest so that the south flank of the fire now became the head of the fire. With the wind shift came new threats to values at risk; Camp Grayling along the shore of Black Lake was approximately 1 km away, and the community of Black Lake was 2.4 km away. Both values were now downwind of the fire. By 1741 hrs, the fire was reported to be only 300 m from Camp Grayling and had started to burn towards the community of Black Lake. 2 Measure of Fire Intensity Class as established by the Canadian Forest Fire Behaviour Prediction System 2 P a g e

7 Crews working to protect Camp Grayling had to pull out for safety reasons at 1753 hrs and by 1754 hrs the fire was reported to be at Camp Grayling. The fire burned over the retardant lines and Camp Grayling itself at 1800 hrs where 20 buildings were burnt, leaving only one main building standing. Fir Island Black Lake Camp Grayling Figure 2 - View from fire origin to the east toward Black Lake along what used to be the north flank of the fire. Smoke shows 90 degree wind switch from initial run, Camp Grayling was just catching on fire. After burning through the outfitting camp the fire continued to spread as a full crown fire towards the community of Black Lake. The Air Attack Officer with the air tankers now focused their attention on the protection of the community. The fire guard that was established nine years earlier stood between the fire and the community. The Air Attack Officer targeted the community side of the fire guard to drop retardant. Four CV 580 drops were made starting at the lake and working up the fire guard. The Air Attack Officer working the fire reported that the fire was still burning at an intensity class 4 with no visible spotting when they left the fire at 2030 hrs. At this time, the Air Attack Officer reported the fire to be approximately 1-2 km away from the fire guard and burning towards the community. 3 P a g e

8 Air Tanker Black Lake Camp Grayling Figure 3 - Camp Grayling burning as Air Tankers lay down a retardant line along the fire guard between the fire and the community. The Fire Centre Duty Officer log book documents the ground crew efforts to protect the community of Black Lake, an edited recall of events is provided below: 17:59 hrs: Helicopter 26, a Bell 205 & Helicopter 70, a Bell 407 are both inbound to the fire. 19:03 hrs: Ground crews assisted by heavy equipment are working to create a fire guard between the fire s east flank and Black Lake (close to the community). 20:42 hrs: Southern part of fire is a fire intensity class 5. Plan to put Helicopter 70 with bucket out to secure a portion of fire that is of concern. 20:48 hrs: Fire staff in helicopter who are monitoring the fire recommend the evacuation of Black Lake. 20:52 hrs: Fire staff in helicopter reports that the fire is still burning at a fire intensity class 5. 21:04 hrs: Fire is reported to have hit the Black Lake fire guard. 21:09 hrs: Fire staff looking to see if they can back burn from fire guard. 21:33 hrs: Report that the fire has started to jump the fire guard. 21:36 hrs: Ground crews are actioning the jump fires. 22:22 hrs: Crews stopped working fire for the night. Fire has calmed down but there is still some open flame. 4 P a g e

9 The author notes that the Air Attack Officer estimated the fire to be burning at an intensity class 4 while the ground crews were calling it an intensity class 5, well after the Air Tankers were off the fire. Two spot fires were found the next day across the fire guard close to the community itself. The spot fires were approximately 15 square meters (m 2 ) in size and only 200 m from homes on the north side of the community. Community of Black Lake Fire Origin Camp Grayling Ice on Black Lake Figure 4 - Overview of Blib fire looking in a westerly direction. 5 P a g e

10 DESCRIPTION OF THE FIRE ENVIRONMENT Fuels Black Lake falls within the Taiga Shield Ecozone and the Tazin Lake Ecoregion 3 in an area where sandy soils dominate along with scattered rock outcroppings. The fire started in a mature Jack Pine stand where the trees are 10 to 15 m in height and cm Diameter Breast Height (DBH). The dry sandy soil in the area makes for a very shallow duff layer. Figure 5 - Picture of the upper sized trees that the post cutters were harvesting within the stand where the fire originated. The forest stands from Camp Grayling to the community of Black Lake are mostly younger and very dense, the result of a 1977 fire. Next to Camp Grayling itself there were some small Trembling Aspen (Populus tremuloides) stands and along the lake there are some stands dominated by 10 m high White Birch (Betula papyrifera) with a Black Spruce (Picea mariana) understory. The picture shown in Figure 6 was taken when the fire guard was being constructed and shows the type of forest that the fire burnt through when it ran to the south towards the community. 3 Units of the Canadian Ecological Land Classification System 6 P a g e

11 Figure 6 - Construction of the fire guard at Black Lake in WEATHER Antecedent Climatic Conditions The Athabasca region reported lower than normal snowfall over the winter season, from November 2014 to May of Cumulative precipitation over this period was somewhere between mm of precipitation compared to mm that this area normally receives. Weather observations taken at each weather station are used to generate Fuel Moisture Codes and Fire Behaviour Indices as part of the Canadian Forest Fire Weather Index (FWI) System. The May 1st Drought Code for this area reflected the dry fall and winter, with levels in the range that indicate a High fire hazard level. These levels indicated a drought code percentile of Dry Conditions, 1 in 10 years. Drought Codes are a rating of the average moisture content in deep, compact, organic layers. The code indicates seasonal drought effects of forest fuels, and the ability of fire to burn in deep duff layers and large logs. High levels indicate that fires will be difficult to control. 7 P a g e

12 Figure 7 - Map of Saskatchewan showing percent normal precipitation for April 01, 2015 to June 15, 2015 compared to stats from The circle at the top indicates the Black Lake area Fire Indices Other components of the FWI System collected from the two nearby weather stations show burning conditions to be at extreme levels on the day of the fire. The Stony Rapids weather station is an Environment Canada weather station located 30 km northwest of the fire and the Beatrice weather station is a provincial weather station located 37 Km southeast of the fire. FWI components that indicate Extreme burning conditions are indicated in red font within Table 1. Table 1: Fire Weather Indices for the fire area taken from two nearby weather stations on the day of the fire. Weather readings are noon actuals (Central Standard Time) and are used to forecast for burning conditions at 1600 hrs based on the normal diurnal curve. Wx Stn. Temp. RH W Dir W Spd Rn 24 FFMC DMC DC ISI BUI FWI Stony R 23 C 18 WSW Beatrice 24 C 15 WSW Surface Weather Observations Weather for the day of the fire run comes from the Stony Rapids weather station which is located 30 km to the north west of the fire. Crossover conditions were in effect for the first two hours of the fire run where temperatures were higher than the relative humidity levels. The crossover conditions combined with relatively high wind speeds during the first four hours of the fire resulted in strong fire runs. The humidity sharply rises towards midnight and the temperature drops significantly. 8 P a g e

13 The fire area received a couple hours of snow starting in the early morning hours of May which effectively prevented any further spread. Table 2: Surface Weather Observations from the Stony Rapids Weather Station for May 15th from 1500 hrs 2300 hrs. Wx Station Date Time Temp Dew RH Wind Dir. Wind Speed Wind Gust STNYR 15-May N 4 NULL STNYR 15-May E 13 NULL STNYR 15-May N 9 NULL STNYR 15-May N 9 NULL STNYR 15-May N 11 NULL STNYR 15-May N STNYR 15-May W STNYR 15-May W STNYR 15-May W Table 3: Surface Weather Observations from the Beatrice Weather Station for May 15th from 1500 hrs 2300 hrs. Wx Station Date Time Temp Dew RH Wind Dir. Wind Speed Wind Gust BEATR 15-May NE BEATR 15-May N BEATR 15-May N BEATR 15-May NNE BEATR 15-May N BEATR 15-May NW BEATR 15-May W BEATR 15-May W BEATR 15-May W P a g e

14 Table 4 below shows the hourly adjusted Fine Fuel Moisture Conditions, Initial Spread Index and Fire Weather Indices. Red numbers indicate extreme burning conditions. Table 4: Hourly FFMC, ISI and FWI from the Beatrice weather Station for May 15th from 1500 hrs 2300 hrs. Wx Date Time FFMC_h ISI_h FWI_h Station BEATR 15-May BEATR 15-May BEATR 15-May BEATR 15-May BEATR 15-May BEATR 15-May BEATR 15-May BEATR 15-May BEATR 15-May The May 15 th 18Z (1200 local) surface analysis (Figure 8) shows a surface ridge influencing the fire area bringing sunny and dry weather. In the North West Territories a cold front is moving southward. The 1800 local surface prognosis (Figure 9) shows the front just north of the fire location, but in reality the front was slightly faster than forecasted and passed over the fire area around 1800 local. We can see from the isobars a strong wind shift with the frontal passage from Southwest/West to Northwest/North. The 0000 local surface prognostic (Figure 10) shows the cold front south of the fire area. The high pressure in the NWT is an artic high, which will account for the couple of hours of snow during the early morning of May The surface analysis for 12Z (0600 local) (Figure 11) verified the prognosis chart for a frontal passage over the fire on May P a g e

15 Figure 8 18Z (1200Local) surface analysis. 11 P a g e

16 Figure local surface prognosis May P a g e

17 Figure local surface prognosis May P a g e

18 Figure 11 12Z (0600 local) May surface analysis Topography The fire started in a relatively flat area at approximately 250 m in elevation and burned into some small hills with 10 to 20 m rise of elevation before dropping down 40 m where it crossed the Fond du Lac River. On the other side of the river there is a quick rise in elevation to a top of a ridge along the edge of the lake that tops out at 350 m before sharply dropping down to the lake edge. When the fire ran back to the west it immediately crossed a 1 km ridge of sharp hills that rise approximately 40 m in elevation. Once over the hills, the fire spread in relatively flat terrain up to the fire guard. 14 P a g e

19 FIRE BEHAVIOUR Observed Rates of Spread Documentation to determine exact rates of spread on this fire are limited. Based on comments and timelines from the Air Attack Officer working the fire, the documented rate of spread from when wind switched to when it hit Camp Grayling was 31 m/min. Projected Rates of Spread The observed rate of spread falls within the lower threshold of the projected rate of spread which was determined to be m/min based on weather from the two closest weather stations and using the C 3 fuel type. Once the fire burnt through the mature forest stand and hit the younger, thicker stands that were closer to the lake, the rates of spread are projected to be between m/min when using the C- 4 fuel type. Fire Behaviour The resulting fire scar clearly shows the extreme burning conditions that were present. Once ignited, the fire quickly transitioned from a surface fire to a full crown fire. A brief period when the wind switched direction resulted in reduced rates of spread but the fire quickly moved into a full crown fire once the winds stabilized. The fire continued to run as a full crown fire right up to when the fire reached the fire guard at 2104 hrs. The fire was able to spot across onto Fir Island, a distance of at least 700 m. Other spotting that was documented occurred when the fire hit the fire guard where it was able to jump the guard to ignite the forest on the far edge of the break, a distance of 90 m. The fire spotted approximately 450 m when it jumped the break and ignited two small spot fires within 200 m of the community itself. Map of Fire Projection A Prometheus 4 fire growth projection was completed to determine how far the fire would have travelled if the fire guard would not have been in place. A 3 hour projection was completed using line ignition along the 1.25 Km front where the fire burnt up to the fire guard. The projection starts when the fire was observed reaching the fire guard at 2100 hrs. Table 5: The weather data used to run the Prometheus fire growth projection. 4 Prometheus is a Fire Growth Model 15 P a g e

20 Figure 12 - Prometheus wildfire projection showing the projected advancement of the fire from 2100 hrs to 0000 hrs. FUEL BREAK AND FIRE INTERACTION The community of Black Lake had a fire guard constructed around the perimeter of the community in 2006 when it was threatened by another wildfire. The fire guard was constructed using dozers where the trees were windrowed in the middle of the break. The fire guard is approximately 90 m in width where the fire hit it at the west end and is 60 m wide closer to the lake where the fire guard makes a corner around a wet drainage. See Figure 13 for more detail. Note that the sewage lagoon seen in the above picture has been filled in and is actually an open grass area between the fire guard and the community. 16 P a g e

21 1.25 Km fire front Figure 13 - Picture looking in a southerly direction showing the burn scar indicating a full crown fire as fire hit the fire guard. Note the retardant line on the community side of the guard and the slash pile in the middle of the guard. The fire guard was constructed approximately 0.75 Km from the community of Black Lake and ties into the lake on both sides of the community. Note the new cat line on the west flank of the fire. The fire guard had grown up somewhat from when it was constructed; there was a moss / lichen layer along with some scattered Black Spruce and Jack Pine seedlings that were less than 1 m in height. Very little to no other slash was present as the area had been stripped to mineral soil by the dozers to build the guard. See Figure 14 to see a close up of the vegetation on the fire guard. 17 P a g e

22 Figure 14 - Close up of fire guard showing some sparse Black Spruce and Jack Pine regen coming up on the cleared site. The fuel break was utilized tactically in the suppression of the fire. Air tankers were called in to try to prevent the fire from running into the community of Black Lake. CV 580 air tankers dropped four loads of retardant, working up from the shoreline on the community side of the fire guard. The tankers started dropping at 1940 hours and left at 2030 hrs. The Air Attack Officer reported the fire to be 1 2 km back from the fuel break and burning at an intensity class 4 with no visible spotting when they left. A vehicle trail along the edge of the fire guard provided safe access to the head of the fire for the fire crews. The crews utilized the guard to start a small scale backfire of the fuels before the fire reached the fire guard. When the fire did reach the guard, ground crews and helicopter support were able to see the spot fires that crossed the guard and were able to safely and successfully suppress them before they built up any intensity. The crews also used the break as an anchor point to build a cat guard up the west flank of the fire line. 18 P a g e

23 Figure 15 - Left, an aerial picture of the tanker drops along the community side of the fire guard and Figure 16 showing the fire approaching the fire guard when the tankers left the fire at 2030 hrs. Burn patterns show that the fire was still burning as a full crown fire when it hit the fuel break in multiple locations over a 1.25 km front. The fire burnt through the guard in a couple locations but wet areas combined with the retardant drops helped to limit further spread. The fire crews were able to safely access and suppress the spot fires where the fire started on the community side of the break. The brush pile in the centre of the fire guard caught on fire but there was enough cleared area to limit any further spread from the piles. Fire crews stationed themselves within the community of Black Lake and patrolled the area for spot fires from 2200 hrs to 2300 hrs. Two spot fires, both approximately 15 m 2 in size were located the next morning, approximately 200 m north of the community edge. 19 P a g e

24 CONCLUSION May 15, 2015 saw some extreme burning conditions in the Black Lake area and an ignition source combined with continuous fuels resulted in a fast moving and destructive wildfire. The 90 degree wind switch compounded the difficulty factor in suppressing this fire and significantly added to the size and force of it. It is important to note that there was no fuel management work completed around the outfitting camp and extreme fire behaviour resulted in the fire burning through the camp area destroying all but one building. Air Attack Officers working the fire were able to utilize the fire guard to effectively lay a retardant line along the community edge of the fire guard. Photo evidence shows locations where the fire burnt into the retardant line in some locations but not through it. The lineal fire guard served as an ideal location for the air tankers to build upon to make an effective retardant line. The guard provided a safe access for the firefighters where they were able to locate and focus on the spot fires that came up across the break. The ground crews also used the break to start a backfire along a portion of the fire guard which would have limited the spotting that occurred over the break when the fire front hit the backfire. The fire guard played a significant role in the protection of the community of Black Lake itself. Although burning conditions were quickly deteriorating by the time the fire hit the break the fire was still burning as a full crown fire and there would have been no way that the available suppression resources would have been able to slow the fire if it were not present. Fire modelling puts the fire into the north edge of the community by midnight if the fire guard was not in place, even with the deteriorating burning conditions. Considering the extreme fire behaviour and the distance of the spot fires that were observed on this fire, the fire guard would not have been as effective if the fire would have hit it a couple hours earlier. A consideration to make the fire break more effective would have been to thin the community side of the break so that any spot fires that start across the break would be slow to build up intensity and therefore be easier suppressed by air and ground crews. 20 P a g e