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It’s 4 am on a mid-August morning in the northern California wilderness.
During a brief overnight storm,
lightning strikes the top of a hill
ignites some dry underbrush and starts a wildfire
It isn’t until 6am as the sun rises
that someone notices the fire
a hiker camping on an overlooking Hill
as soon as the hiker’s 911 call is received by the dispatch center
they contact Cal Fire
the agency responsible for wildfire protection and management in California.
By 6:30, they call the Redding, California based smokejumpers.
They are one of most elite firefighting squads in the United States.
There are only 400 smokejumpers in the US
and 40 of those are based here in Redding, California.
They’re essentially the rapid response team for wildfires.
Within 15 minutes of receiving the call,
these smokejumpers are in their plane and taking off.
It takes just 20 minutes to fly the 50 miles to the fire site
where they find a suitable tree-free landing spot,
紧接着灭火员跳机 展开降落伞 着陆
jump, deploy their parachutes, and land.
The plane then circles back to parachute down boxes of equipment.
Smokejumpers carry with them enough supplies to last 72 hours completely self supported
食物 水 帐篷 安全装置和灭火工具
food, water, shelter, safety equipment, and firefighting tools.
They follow the ridge line and make their way to the fire. Now,
this is a small team and
they need to decide how to prioritize what they do.
the fire already have grown 15 acres
the team knows they’re unlikely to stop it on their own,
backups are already on the way,
so their priority is to slow it down as much as possible.
There are four major factors that affect how fast a fire moves:
how much fuel there is, how wet the fuel is,
the wind direction, and the slope.
The two factors that the team can immediately gauge
that affect where the fire will move
the fastest are the wind direction and slope.
In this case the wind is coming from the north
and they know that to the south-west is an upward slope.
Fire moves faster uphill than it does downhill
since fire burns upwards so these smokejumpers
know that this is likely the fire’s fastest moving front.
While trees do burn,
the primary source of fuel that a wildfire uses to move is the dry
brush and dead wood on the forest floor
so the biggest technique used to stop forest fire
is to create what’s called a fire line.
These are essentially a gap where they remove all fuel
plants both dead and alive
so that there’s nothing for the fire to continue burning.
the smokejumpers use a mix of chainsaws
and other hand tools to do this work
but sometimes fire lines are pre-built
in this case there’s a road at the top of the uphill section
which will help slow or stop the fire
so they can direct their efforts elsewhere
They use the road as their anchor point
a cleared section that the fire likely won’t cross where
where they start building their fire line
so the fire can’t outflank them.
Throughout this construction process
the smokejumpers need to be sure that they can escape in case
the winds shift or the fire picks up speed.
wildfires can move exceptionally fast up to seven miles per hour in forest
which is faster than humans are often able to make their way through dense trees.
in grasslands fires can move up to 14 miles per hour
so firefighters have to be extra cautious.
For this reason firefighters rarely put themselves directly in front of the fire’s moving front
they are either be far ahead or to the side.
In the case of this fire
as they’re building this first fire line
they’re close to a road which acts as an easy exit point
but just in case all smoke jumpers carry fire shelters
These compact, lightweight shelters won’t survive direct flames for too long
but they do greatly increase a firefighter’s chance of survival
in case they can’t escape the path of the fire.
after a little over an hour of work
the smokejumpers completes a continuous fire line from the road to a stream
Streams, while less secure than roads,
also help stop or slow down a fire by acting as a fire line.
To the south-east of the fire
there’s also a small road that connects to another stream
meaning there are at least rudimentary fire lines on three sides of the fire.
It’s at this time when backups arrive by road.
The added manpower allows for much faster action.
the immediate focus goes to strengthening the southeastern fire line
currently just a stream
at closest the fire is less than 100 feet from the stream
the stream is itself in a valley
so it’s too risky to work directly behind the stream,
there’s just no good escape route
so the new arrivals get to work
on a redundant fire line 100 feet behind the stream.
By 10 am the fire has further grown
and the team knows that the worst is still to come.
fire spreads most rapidly between 10 a.m. and sunset due to the daytime heat and wind.
by 11 a.m. the fire has reached the road and part of the fire line
which means that some of those who are building the fire line are re-allocated
to make sure that the fire-line holds extinguishing any flames that may jump the road.
By noon the fire lines are holding
and all the fire size is growing it’s at a manageable pace
so there’s reasonable hope that it can be suppressed before expanding to an uncontrollable size
At 1pm, though, conditions change.
The wind starts blowing harder towards the south-west
and as trees burn on the north side of the road,
the wind pushes embers over the road which ignite underbrush on the other side
and now the entire focus of the firefighting efforts change.
You see, the point of fighting wildfires is not actually to put them out,
it’s to control them.
While the number of wildfires has increased due to humans
they’re actually a very natural phenomenon.
What’s making wildfires worse is humans stopping them.
Many forests survive wildfire
through trees having heat-resistant bark and other evolutionary adaptations.
These fire resistant forests relied on having wildfires
at a consistent interval every few decades to clear out the forest floor of dead plants
and to kill invasive species.
nowdays though, as humans suppress fires
a forest might only see a wildfire every 50 years years instead of 25,
for example, meaning that there’s twice as much fuel
能让火燃烧的更快 更广 更凶猛
and so the fire burns faster, larger, and more intensely.
It was only until recent years that the research revealing this was widely accepted
so the goals of firefighting shifted from stopping wildfires completely to controlling them.
In some places, being a firefighter actually means starting fires.
Fire management agencies will conduct controlled burns
in order to reduce the risk of an uncontrollable fire
and to increase the health of a forest.
while forests can survive wildfires humans cannot
so most agencies will let fires burn in a controlled fashion
up until the moment they risk damaging property or threatening human life.
This fire that jumped the road just did exactly that.
At the bottom of this slope is a town
and the fire is now headed in that direction
with no preexisting features to stop it.
That means that all measures must be taken
to aggressively stop the fire’s expansion to the west.
that means it’s time to bring out the big guns
it’s time to attack the fire from above.
Planes and helicopters are some of the most effective tools used to fight wildfires.
They can quickly and accurately drop huge amounts of water or fire retardant.
The decision to use aerial firefighting does not come lightly
as it’s both hugely expensive
and using an aircraft on one fire
means it can’t be used on another
Their use needs to be prioritized for the most dangerous fires.
There’s also a decision to be made
on what the aircraft is going to drop—water or flame retardant.
Water is cheap and, with some aircraft designs,
can be reloaded near the fire without landing at an airport.
Water is only effective at extinguishing flames,though.
Flame retardant, on the other hand,
can be used to stop flames from starting.
it can essentially create a fire line ahead of the fire spread
as it will stop a line of forest from burning.
The main issues, though,
are that flame retardant can only be loaded at an airport
and it’s a very expensive
A gallon of Phos-Chek,
the most commonly used brand of flame retardant, costs $ 3.
that’s about the same as a gallon of milk at the grocery store
but these aircraft use thousands of gallons of it for each drop.
举例来说 世界最大的灭火飞机 747超级灭火机
The world’s largest firefighting aircraft,the 747 supertanker
for example carries 19 thousand six hundred gallons of flame retardant
meaning that what it uses in one drop costs nearly $60,000.
Of course there’s a reason agencies hire this plane,
it creates a three-mile long fire line almost instantly
but it comes at a steep price.
For this fire, using such an expensive tool would be overkill.
In this case, they’ll use a helicopter with a bucket attached.
the bucket is filled with water from a nearby lake
then the helicopter flies over to the fire and drops it.
With only 5 miles to the lake
the helicopter is able to make a drop about every 5-10 minutes
and while it works on stopping the spread on one side
hand crews work on building a fire line on the other.
the area that the helicopter extinguishes essentially acts as its own fire line
as fire can’t burn what’s already burned.
This work continues for the next few hours
It’s vital to not let anything to the south-west
of the road burn out of control.
By 4pm the outbreak is managed
and attention can be directed back to the largest section of the fire
As the afternoon wears on
some crews get back to lengthening the eastern fire line
others begin constructing a western fire line,
and the helicopter works on slowing the advancement to the north.
By the time the sun begins to set around 8,
all sides of the fire have at least some element of control
so that during the night and in the coming days
the fire can continue to burn in a controlled fashion
until there’s nothing left to burn.
This mission was a success
but the reality is that this is not a real fire
Real fires rarely end this well.
Real fires don’t act so predictably
because real fires can’t be predicted.
real fires are a menace that can grow to the size of small countries
and can burn for months.
During summer and fall,
there are often more than 100 large forest fires
burning around the US at any given time
and thousands more around the world
no firefighting effort is exactly like another
but these are the primary techniques used
by those who work everyday to protect life and property
from one of nature’s most dangerous phenomenons.
whether you’re fighting forest fires or running a business
the tools you use are crucially important.
In both cases they directly affect how well you do your job
and while chainsaws, axes,
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使用方形空间 就可以轻松运营博客 组合网站 网店
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