“From 1948 to 2006, storms measured at extreme precipitation
increased 18% in the Pacific coastal states, including a 26% jump in
California, according to a 2007 analysis of federal climate data by
Environment California, an environmental group based in Los Angeles.
In the Los Angeles area, data show a 58% increase in torrential
“”There is very little we can do effectively if it rains really hard,
except to get out of the way.”
Wall Street Journal
September 2, 2008
Suspect: Global Warming
Now, Big Mudslides
By JIM CARLTON
BIG SUR, Calif. — Add mudslides to the mix of global-warming worries.
With California’s fire season in full swing, residents in charred
areas such as the one around this bucolic resort face the prospect of
catastrophic slides on newly denuded hills when winter rains return.
Mudslides often follow big fires as part of a natural process that
has gone on for millennia in the West. But forestry experts are
increasingly concerned about a noticeable upswing in torrential
downpours in California that threatens to send even more mud and
debris cascading into downstream communities.
The most likely culprit, scientists and other experts say, is climate
change. Increased downpours are consistent with the predicted impacts
of global warming, as higher temperatures cause more ocean water to
evaporate, making for stronger storms.
“We know fires are going to continue in that Mediterranean climate,”
says Wally Covington, a forestry professor at Northern Arizona
University. “The question is, is there likely to be an
intensification of rain, which will mean a river of mudslides.”
The evidence, so far, suggests that the answer is yes. From 1948 to
2006, storms measured at extreme precipitation increased 18% in the
Pacific coastal states, including a 26% jump in California, according
to a 2007 analysis of federal climate data by Environment California,
an environmental group based in Los Angeles. In the Los Angeles area,
data show a 58% increase in torrential storms.
The torrents of mud may be the latest in a series of stealth impacts
of climate change suggesting a complex chain reaction. Bark beetle
infestations have killed millions of coniferous trees from New Mexico
to Alaska as drought and warmer temperatures — which many experts
attribute to climate change — have made the trees more susceptible
to attack. Scientists have been surprised by a rash of polar bear
drownings in the Arctic, as sea ice has retreated too far in places
for the bears to swim to safety.
Others say the impacts of global warming are overblown and that fires
and other phenomena are unrelated to one another or are part of a
natural process. Mudslides are likely to prove another point of
In July, an unusually robust thunderstorm over the Sierra Nevada
dumped as much as three inches of rain on fire-scorched hillsides in
two hours, unleashing a wall of mud three feet high into communities
around Lake Isabella below. About 50 homes suffered damage, highways
were closed and dozens of people were trapped — including 60
firefighters battling a wildfire.
“You have increasing frequency of all the key conditions to
mudslides: bare hills and heavy rains,” says Elizabeth Ridlinger,
policy analyst at Environment California. “And clearly the increase
in heavy rains can be tied to climate change.”
Also, more of California’s precipitation is falling as rain instead
of snow. According to an August report from the University of
California at Davis, the amount of precipitation that fell as snow at
Lake Tahoe decreased to 34% in 2007 from 52% in 1910.
Researchers on the Environment California report say it is too early
to tell whether mudslides have actually increased in tandem with the
more-frequent downpours, since their report, one of the first on the
subject, focused only on the precipitation. But mudslides are
considered so dangerous — 16 campers died when slides from
fire-charred slopes in Southern California engulfed them on Christmas
Day 2003 — that state and federal teams are swarming across burn
zones in the state to come up with contingency plans. With the worst
fire season on record in California, emergency crews expect trouble.
“Once the brush is burned, the stage is set,” says Kevin Cooper, a
wildlife biologist for the Los Padres National Forest surrounding Big
Sur. “There is very little we can do effectively if it rains really
hard, except to get out of the way.”
Mr. Cooper is part of a federal team that has just completed its
mudslide assessment for the so-called Basin Complex fire, which
burned 240,000 acres of brush and trees in the Santa Lucia Mountains
overlooking Big Sur. The team’s preliminary conclusion: A 40-mile
stretch of the California coast, including Big Sur, is at an
“extremely high” risk of mudslides this winter.
On a recent inspection of Julia Pfeiffer Burns State Park, associate
civil engineer Joan Carpenter, who works for the California
Department of Parks and Recreation, stopped her truck at a narrow
culvert beneath California Highway 1 where she said mud and debris
from the blackened slopes above would likely clog and then overflow
in a heavy rain. “It’s going to be ugly here,” Ms. Carpenter said.
At Big Sur, a community of about 1,500 situated at the base of
mountain peaks stripped of much of the vegetation that held back
rocks, boulders and other debris, some longtime residents are
comparing the threat of mudslides to 1972, when a river of debris
poured into town following wildfires.
Don McQueen, 79 years old, whose family owns property along a creek
where officials say more slides are likely, recalls: “The mud came
out of the canyon 30 miles per hour, carrying boulders as big as a
Write to Jim Carlton at email@example.com