Tag Archives: California

Fires in Paradise: Exposure Growth and Catastrophe Risk in the Wildland-Urban Interface

Like many communities in California with a mild climate, affordable housing, and scenic wilderness, Butte County (pop. ~230,000) has grown significantly over the past four decades. Broadly, this growth is happening all around the county — both in cities (e.g. Chico, the county seat and largest city, pop. ~94,000) as well as in more rural areas. Looking more closely, however, the specific spatial patterns of Butte’s development reveal conditions that set the stage for the ongoing Camp Fire to become one of the deadliest and most destructive fires in California history.

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The HayWired Earthquake Scenario: An RMS View on Fire Following Earthquake Risk

New findings into the effect of a magnitude 7.0 earthquake originating from the 74 mile-long (119 kilometer) Hayward Fault in the California Bay Area, suggests that fire following earthquake alone could see more than 52,000 single-family homes burn. Earlier this month, the United States Geological Survey (USGS) released new results for their HayWired scenario, a scientifically plausible magnitude 7.0 earthquake on the Hayward fault. The hypothetical HayWired earthquake occurs at 4:18 p.m. on April 18, 2018, the anniversary of the magnitude  7.8 earthquake which struck San Francisco in 1906. The mainshock ruptures the fault along its length for about 52 miles (83 kilometers). The impact of such an event on one of the most densely populated and interconnected areas of the U.S. West Coast — with a population of about seven million people — would be disruptive.

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The California Earthquake Authority (CEA) and RMS Co-host Webinar to Share Insights on California Earthquake Risk Using North America Earthquake Version 17.0

Together with the California Earthquake Authority (CEA), RMS co-hosted a webinar on May 17 for the CEA’s global panel of catastrophe reinsurers to explore how new earthquake science and RMS modeling impacts the CEA and its markets. The CEA is one of the largest earthquake insurance programs in the world with nearly one million policyholders throughout California. In the webinar, we analyzed and shared insights about the risk to the CEA book using the new Version 17 RMS North America Earthquake Models which was just released on April 28.

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What If The Oroville Dam Had Collapsed Completely?

RMS modeling reveals the wider risk of U.S. flooding, and a significant protection gap

A combination of heavy rainfall and melting snow had filled Lake Oroville in northern California near to its capacity. Dam operators released water through the main spillway to control the reservoir level, but a 300-foot hole unexpectedly emerged, and the surrounding soil was eroded by the water gushing out. Spillway outflows were reduced to stop the erosion.

Satellite images of Oroville Dam after the heavy rainfall in mid-February (Source: California Department of Water Resource)

Oroville Dam after heavy rainfall in mid-February (Source: California Dept of Water Resource)

But this made the problem with rising reservoir levels worse, as the water then began to flow over the emergency spillway. On February 12, 2017, at least 188,000 residents were told to evacuate, while trucks and helicopters dumped over 1000 tons of material per hour on the weakened structure to prevent a more significant breach. As water levels in the reservoir subsided, the risk reduced.

With no massive discharge or flooding, insurance losses are expected to be limited to coverage for business interruption, loss of use, or additional living expenses (ALE) incurred by the evacuees.

It could have been far worse if the dam had completely failed – this was a worrying near-miss.

Dam failure, though rare, is not a negligible risk.  In fact, a similar near-miss situation occurred during the 1971 San Fernando earthquake where the lower Van Norman Dam was a near-breach and forced the evacuation of 80,000 people. Our modeling teams decided to model a counter-factual version of February’s Oroville Dam breach, in which either (i) the dam continues to disintegrate in a controlled manner or, (ii) in the worst-case scenario, it collapses.

Our flood modelers, Ye Tian and Sonja Jankowfsky, simulated these ‘what if’ scenarios over a 72-hour cycle, using reservoir water level data from the California Data Exchange Center’s Department of Water Resources, and their own estimation of the lake’s bathymetry (contours of the lake bed) and capacity.

The worst-case scenario is modeled assuming the height of the dam wall becomes ‘zero’ instantaneously – for example, as might happen if there was an explosion due to sabotage. For the controlled breach scenario, the dam wall is gradually lowered at two meters per hour to simulate what could have happened had the erosion of the dam continued.

In our modeling, the amount of discharged water would be expected to overwhelm local flood control measures over 100 miles downstream, as was evidenced by the widespread flooding in the simulations. We estimate that under either scenario, about $21.8 billion of building value would be at risk, which, for the communities near Oroville, would be a huge problem because much of it is uninsured.

Insurance coverage is one of the most effective ways of ensuring a region re-bounds quickly after disaster, but in the Oroville region flood insurance penetration is fairly low. Most property owners rely on the National Flood Insurance Program (NFIP), which is most commonly sold to homes in the 100-year flood plain along the Feather River.

FEMA 100-year flood zones

FEMA 100-year flood zones

Potential inundation depths simulated for a complete and instantaneous collapse of the Oroville Dam

Potential inundation depths simulated for a complete and instantaneous collapse of the Oroville Dam

This flood plain is shown as blue areas in this map. Compare that to the map below.








This map (right) shows modeling from the RMS ‘what if’ scenario of the Oroville Dam breach. The 100-year flood plain (map above) covers significantly less area than that which would be inundated if the dam breached (map right).

So, why does this matter? Residents living outside the 100-year flood zone are not required to purchase flood insurance, and therefore most do not. These areas include the towns of Biggs, Gridley, Live Oak, Oroville, South Oroville, Thermalito, and Yuba City. And yet as RMS modeling shows, many of those communities would have experienced major flooding if the dam had breached completely.

The Protection Gap

It is obvious that NFIP flood zone maps do not include dam failure scenarios, and yet these failures typically inundate a much wider area beyond the naturally occurring flood plain, because the volume of water and speed of release overwhelms natural and man-made defenses.

FEMA cannot quickly nor easily change the flood maps to incorporate this type of risk explicitly. At RMS, we are developing tools to quantify these kinds of extended risks to allow the private flood insurance market to step in and fill the current gaps in coverage.

Thankfully, our ‘what if’ scenario didn’t become a reality. But it highlights the risk of aging infrastructure which may not be able to withstand extreme weather events. Nationwide, the National Inventory of Dams indicates that of the 90,580 situated across the U.S., over 30% exhibit significant to high hazard potential due to structural deterioration.

[Note: clients can obtain modeling files for the Oroville Dam analysis from RMS account managers. This blog has been edited to provide further detail on the initial dam failure.]

“San Andreas” – The Scientific Reality

San Andreas—a Hollywood action-adventure film set in California amid not one, but two magnitude 9+ earthquakes in quick succession and the destruction that follows—was released worldwide today. As the movie trailers made clear, this spectacle is meant to be a blockbuster: death-defying heroics, eye-popping explosions, and a sentimental father-daughter relationship. What the movie doesn’t have is a basis in scientific reality.

Are magnitude 9+ earthquakes possible on the San Andreas Fault?

Thanks to the recent publication of the third Uniform California Earthquake Rupture Forecast (UCERF3), which represents the latest model from the Working Group on California Earthquake Probabilities, an answer is readily available: no. The consensus among earth scientists is that the largest magnitude events expected on the San Andreas Fault system are around M8.3, forecast in UCERF3 to occur less frequently than about once every 1 million years. To put this in context, an asteroid with a diameter of 1,000 meters is expected to strike the Earth about once every 440,000 years. Magnitude 9+ earthquakes on the San Andreas are essentially impossible because the crustal fault zone isn’t long or deep enough to accumulate and release such enormous levels of energy.

My colleague Delphine Fitzenz, an earthquake scientist, in her work exploring UCERF3, has found that, ironically, the largest loss-causing event in California isn’t even on the San Andreas Fault, which passes about 50 km east of Los Angeles. Instead, the largest loss-causing event in California is one that spans the Elsinore Fault and runs up one of the blind thrusts, like the Compton or Puente Hills faults, that cuts directly below Los Angeles. But the title Elsinore + Puente Hills doesn’t evoke fear to the same degree as San Andreas.

Will skyscrapers disintegrate and topple over from very strong shaking?

Source: San Andreas Official Trailer 2

Short answer: No.

In a major California earthquake, some older buildings, such as those made of non-ductile reinforced concrete, that weren’t designed to modern building codes and that haven’t been retrofitted might collapse and many buildings (even newer ones) would be significantly damaged. But buildings would not disintegrate and topple over in the dramatic and sensational fashion seen in the movie trailers. California has one of the world’s strictest seismic building codes, with the first version published in the early part of the 20th century following the 1925 Santa Barbara Earthquake. The trailers’ collapse scenes are good examples of what happens when Hollywood drinks too much coffee.

A character played by Paul Giamatti says that people will feel shaking on the East Coast of the U.S. Is this possible?

First off, why is the movie’s scientist played by a goofy Paul Giamatti while the search-and-rescue character is played by the muscle-ridden actor Dwayne “The Rock” Johnson? I know earth scientists. A whole pack of them sit not far from my desk, and I promise you that besides big brains, these people have panache.

As to the question: even if we pretend that a M9+ earthquake were to occur in California, the shaking would not be felt on the East Coast, more than 4000 km away. California’s geologic features are such that they attenuate earthquake shaking over short distances. For example, the 1906 M7.8 San Francisco Earthquake, which ruptured 477 km of the San Andreas Fault, was only felt as far east as central Nevada.

Do earthquakes cause enormous cracks in the earth’s surface? 

Source: San Andreas Official Trailer 2

I think my colleague Emel Seyhan, a geotechnical engineer who specializes in engineering seismology, summed it up well when she described this crater from a trailer as “too long, too wide, and too deep” to be caused by an earthquake on the San Andreas Fault and like nothing she had ever seen in nature. San Andreas is a strike-slip fault; so shearing forces cause slip during an earthquake. One side of the fault grinds horizontally past the other side. But in this photo, the two sides have pulled apart, as if the Earth’s crust were in a tug-of-war and one side had just lost. This type of ground failure, where the cracks open at the surface, has been observed in earthquakes but is shallow and often due to the complexity of the fault system underneath. The magnitude of the ground failure in real instances, while impressive, is much less dramatic and typically less than a few meters wide. Tamer images would not have been so good for ticket sales.

Will a San Andreas earthquake cause a tsunami to strike San Francisco?

Source: San Andreas Official Trailer 2

San Andreas is a strike-slip fault, and the horizontal motion of these fault systems does not produce large tsunami. Instead, most destructive tsunami are generated by offshore subduction zones that displace huge amounts of water as a result of deformation of the sea floor when they rupture. That said, tsunami have been observed along California’s coast, triggered mostly by distant earthquakes and limited to a few meters or less. For example, the 2011 M9 Tohoku, Japan, earthquake was strong enough to generate tsunami waves that caused one death and more than $100 million in damages to 27 harbors statewide.

One of the largest tsunami threats to California’s northern coastline is from the Cascadia Subduction Zone, stretching from Cape Mendocino in northern California to Vancouver Island in British Colombia. In 1700, a massive Cascadia quake likely caused a 50-foot tsunami in parts of northern California, and scientists believe that the fault has produced 19 earthquakes in the 8.7-9.2 magnitude range over the past 10,000 years. Because Cascadia is just offshore California, many residents would have little warning time to evacuate.

I hope San Andreas prompts some viewers in earthquake-prone regions to take steps to prepare themselves, their families, and their communities for disasters. It wouldn’t be the first time that cinema has spurred social action. But any positive impact will likely be tempered because the movie’s producers played so fast and loose with reality. Viewers will figure this out. I wonder how much more powerful the movie would have been had it been based on a more realistic earthquake scenario, like the M7.8 rupture along the southernmost section of the San Andreas Fault developed for the Great Southern California ShakeOut. Were such an earthquake to occur, RMS estimates that it would cause close to 2,000 fatalities and some $150 billion in direct damage, as well as significant disruption due to fault offsets and secondary perils, including fire following, liquefaction, and landslide impacts. Now that’s truly frightening and should motivate Californians to prepare.

4 Facts About California’s “Hellastorm”

California is bracing for a major storm this week. Many schools are closed and residents are hunkering down in preparation for potential flooding. Not to be outdone by the East Coast, which has come up with monikers like “snowmageddon” and “snowpocalypse” for their recent storms, some are referring to it as the “hellastorm.”

Source: twitter.com/AllyNgSF

So, what’s the deal with the so-called “storm of the decade?”

It’s getting rainy and windy on the West Coast.

Estimates this morning are predicting 1 to 5 inches of rain from Northern California up to Washington, 1 to 2 feet of snow in the Sierra Nevada mountains, and wind gusts over 50 miles per hour in the interior regions.

It will happen again.

Storms like these are not uncommon, occurring once every 5 to 10 years. So we could experience another one before the end of the decade.

The drought is partially to blame.

While drought conditions are not a necessity for these types of events, they can increase the impact of flooding because the ground cannot absorb water fast enough. The same can occur when the sustained heavy rain falls on ground is already saturated.

The current rain came all the way from Hawaii.

Storms like this are dependent on many variables. In this case, the excessive rain and snowfall is being driven by the position of the jet stream and what’s known as the Pineapple Express, an atmospheric plume of tropical moisture that flows from the sub-tropics near Hawaii to the U.S. West Coast. It generally occurs during El Nino years, but in this case, forecast El Nino conditions did not fully develop. In other words, it’s a weak one.

UPDATE: Northern California has gotten more than 8 inches of precipitation so far. Sustained winds were forecast to be up to hurricane force (70 to 80 mph) in the local mountains and up to 100 mph in the higher elevations across the Sierra summit. A wind gust to 147 mph was recorded at high altitude peak near Lake Tahoe, that had surfers catching 7-foot waves on the lake!

The California Drought: A Shift in the Medium-Term View of Risk

Indications are growing that there is a shift underway in the risk landscape in California that may last several years, prompted by the ongoing severe drought.

It’s no secret that California is a region prone to drought. History shows repeated drought events, and there is emerging consensus that the current drought has no end in sight. In fact, there are indications that the drought could just be getting started.

The situation could be exacerbated by climate change, which is increasing the rates of water evaporation in western regions of the U.S.

We also learned recently that the groundwater levels in Colorado have been depleted by a “shocking” amount, which affects California as a significant amount of water used in the state’s agricultural industry comes from the Colorado basin.

California’s abundant agricultural industry has been fueled by its high sunshine input and the availability of water from the Colorado basin.The state produces nearly half of U.S.-grown fruits, nuts, and vegetables, according to statistics from the California Department of Food and Agriculture.

The sustainability of the agricultural industry is now in question given the emerging information about the security of the water supply, with long-term implications for food production—and therefore prices. While the threat is not to the California economy as farming accounts for little more than two percent of the state’s $2 trillion economy, implications will be to broader food prices and food security issues, as well as the security of those employed to work in this industry.

From a natural catastrophe perspective, we can expect the severity and frequency of wildfire outbreaks to increase significantly for several years to come if current indications prove true. In addition, we can expect that more areas will be impacted by wildfires.

The insurance industry needs to pay close attention to methods for estimating wildfire risk to ensure the risk landscape is accurately reflected over the coming years, just as it adapted in the late 2000s to a forward-looking, medium-term view of the probability of landfalling hurricanes accounting for multi-decadal cycles of increased and decreased hurricane activity in the Atlantic basin relative to the long-term average – and the subsequent consequences for the medium-term risk landscape.