Climate change, including heavy rainfall, is bringing about increasing numbers of mudslides.
That property in the
foothills may look
enticing, but climate
change is driving an
By Alex Wright
The steep slopes of the Rocky Mountains and the Pacific Northwest are prime real estate. But they also host an increasingly dangerous risk: landslides. Landslides wreak, on average, $1 billion to $2 billion worth of damage to properties every year, destroying buildings, roads, power
lines, pipelines and even entire neighborhoods.
Mudslides, one of the most common types of landslide, are caused by extreme
rainfall, earthquakes, wildfires and man-made disasters. They can strike quickly
and they have increased in both severity and frequency in recent years.
Among the worst affected regions are the Appalachian Mountains in the East,
the central Rocky Mountains and the western Pacific Coastal Ranges. These are
home to steep and hilly areas that suffered from years of drought, experienced
forest fires and then got pummeled by flash flooding.
One of the deadliest mudslides in U.S. history was in Oso, Wash., in 2014.
That slide was caused partly by logging activities in the area. When a denuded hill
collapsed after weeks of rain, the resulting slide killed 43 people and destroyed 49
Most at risk are mining and logging companies with extensive operations
at mountain bases and valleys in areas prone to heavy rainfall, flooding and
“Most of the landslides in the U.S. over the last 25 years have been driven by
rainfall,” said Jonathan Godt, program coordinator at U.S. Geological Survey
“A combination of steep topography, abundant material on the mountainsides
and heavy rainfall all converge to create the perfect storm.
“With a growing population and less space in the cities, more people are
moving home or business to the mountains and are putting themselves and their
properties in harm’s way, thus increasing the likelihood of landslides.”
MUDSLIDE VS. MUDFLOW
Gary Marchitello, head of property for North America at Willis Towers
Watson, said that mudslides are primarily caused by excessive rainfall or snowpack
on a slope, or an earthquake.
“A mudslide, by definition, implies that gravity has a part to play,” he said.
“The soil is loosened by the rain or snow, or the ground shaking, and gravity
does the rest.”
Marchitello said that it was important to make the distinction between
mudslides and mudflow, which is caused by river overflow and would typically be
covered under standard flood insurance.
“If you have either flood coverage as part of an all risk policy or you buy it as a
stand-alone peril, you should be covered for mudflow,” he said.
Coverage for damage from mudslides, however, doesn’t come as standard and
requires a separate earth movement
policy or difference in conditions
coverage from a specialty insurer.
“Clearly, if there was a seismic event
that caused a movement of earth to
slide down the mountain, that would be
covered under these separate policies,
“But then there are other
circumstances where you get an excess
of rain or snowfall, which may not
necessarily have anything to do with
the earth shaking, in which case it
could fall into earth movement or
“You need to read your policy
carefully and understand what
you are covered for, if at all,
in terms of earthquake, earth
movement and flood because
there are a lot of nuances.”
— Duncan Ellis, US property practice leader, Marsh
• Increasing frequency and severity
are prompting modelers to focus
more on predicting mudslides.
• Logging and mining companies
are most vulnerable to mudslides.
• Check coverages closely for
distinctions between mudflow,
earth movement and flood.