Climate Cast: Is a “Megaflood” California’s next “Big One?” FEMA flood zones expanding

CC 100 TDC logo.PNG

Every Thursday, MPR meteorologist Paul Huttner joins The Daily Circuit to talk about the latest research on our changing climate and the consequences that we’re seeing here in Minnesota and worldwide.

These days it seems like we are witnessing climate changes unfold right before our very eyes.

It’s not our imagination.

The nature of our seasons is changing. Spring blooms come earlier. Summer is more humid with a documented increase in extreme localized flash flood events…and more frequent droughts. Fall lingers longer. Lakes freeze up later. Winters are trending shorter and noticeably, measurably milder. New plants are able to thrive in Minnesota’s milder climate.

We’re all living witnesses to rapid climate changes in our lifetime. This is no longer your grandparents “Minnesota.”

Jan 9th 008.jpg

A snowless Deephaven Beach on Lake Minnetonka on January 9th, 2012.

Image: Paul Huttner – MPR News

In 2013 at MPR we’re devoting more coverage to the science behind and the growing effects of our changing climate in Minnesota and around the globe.

You can hear me discuss the week’s top climate stories in our new “Climate Cast” every Thursday morning at 9:50am with Kerri Miller on The Daily Circuit.

This week on Climate Cast, meteorologist Paul Huttner joined us to examine how a warming planet could make “megafloods” more likely. We also took a look at FEMA’s new flood maps that significantly expand flood zones.

Climate Cast for Tuesday, February 5th:

Here is an edited transcript of this week’s Climate Cast.

Could the next “Megaflood” be California’s next “Big One?”

They call them “Atmospheric Rivers.”

These “Pineapple Express” jet streams race over the tropical Pacific, then slam into the California Coast. Like a fire hose on the loose, they snake back and forth over time, spraying moisture into different areas of the West Coast.

185 AR.gif

The good news? These “AR induced” storms can produce as much as 50% of California’s average annual rain & precious mountain snowfall.

The bad news? Once every 200 years or so these wildly snaking fire hoses get stuck in place. These “AR Plumes” can carry as much water as 10 Mississippi Rivers, drenching the Sierra Nevada Range and producing massive “Mega Floods” in California’s massive Central Valley.

The last time it happened was 1861-1862, Sacramento, (now a city of 1.2 million people) was inundated with floodwaters 10 feet deep.

CC CAHistoryRmCAStateLib_csl_011.jpg

Will the observed increase in atmospheric water vapor make these storms more frequent and more severe?

A recent artice in Scientific American says they could.

The intense rainstorms sweeping in from the Pacific Ocean began to pound central California on Christmas Eve in 1861 and continued virtually unabated for 43 days. The deluges quickly transformed rivers running down from the Sierra Nevada Mountains along the state’s eastern border into raging torrents that swept away entire communities and mining settlements.

The rivers and rains poured into the state’s vast Central Valley, turning it into an inland sea 300 miles long and 20 miles wide. Thousands of people died, and one quarter of the state’s estimated 800,000 cattle drowned. Downtown Sacramento was submerged under 10 feet of brown water filled with debris from countless mudslides on the region’s steep slopes. California’s legislature, unable to function, moved to San Francisco until Sacramento dried out–six months later. By then, the state was bankrupt.

CC ARkSTORM_webbanner2_690x202.jpg

A USGS project called ARkSTORM simulated what would likely happen in the next big “AR induced Mega Flood” event.

The impacts could make the effects from hurricanes like Sandy & Katrina look like a walk in the park.

Key Findings

1. Megastorms are California’s other “big one.” A severe California winter storm could realistically flood thousands of square miles of urban and agricultural land, result in thousands of landslides, disrupt lifelines throughout the state for days or weeks, and cost on the order of $725 billion. This figure is more than three times that estimated for the ShakeOut scenario earthquake, that has roughly the same annual occurrence probability as an ARkStorm-like event. The $725 billion figure comprises approximately $400 billion in property damage and $325 billion in business-interruption losses. An event like the ARkStorm could require the evacuation of 1,500,000 people. Because the flood depths in some areas could realistically be on the order of 10-20 ft, without effective evacuation there could be substantial loss of life.

2. An ARkStorm would be a statewide disaster. Extensive flooding is deemed realistic in the California Central Valley, San Francisco Bayshore, San Diego, Los Angeles and Orange Counties, several coastal communities, and various riverine communities around the state. Both because of its large geographic size and the state’s economic interdependencies, an ARkStorm would affect all California counties and all economic sectors.

3. An ARkStorm could produce an economic catastrophe. 25% of buildings in the state could experience some degree of flooding in a single severe storm. Only perhaps 12% of California property is insured, so millions of building owners may have limited or no ability to pay for repairs. That degree of damage would threaten California with a long-term reduction in economic activity, and raise insurance rates statewide — perhaps nationwide or more — afterwards.

4. An ARkStorm is plausible, perhaps inevitable. Such storms have happened in California’s historic record (1861-62), but 1861-62 is not a freak event, not the last time the state will experience such a severe storm, and not the worst case. The geologic record shows 6 megastorms more severe than 1861-1862 in California in the last 1800 years, and there is no reason to believe similar events won’t occur again.

5. The ARkStorm is to some extent predictable. Unlike for earthquakes, we have the capability to partially predict key aspects of the geophysical phenomena that would create damages in the days before an ARkStorm strikes. Enhancing the accuracy, lead time, and the particular measures that these systems can estimate is a great challenge scientifically and practically.

6. Californian flood protection is not designed for an ARkStorm-like event. Much has been done to protect the state from future flooding, but the state’s flood-protection system is not perfect. The existing systems are designed among other things to protect major urban areas from fairly rare, extreme flooding. The level of protection varies: some places are protected from flooding that only occurs on average once every 75 years; others, on average every 200 years. But the levees are not intended to prevent all flooding, such as the 500-year streamflows that are deemed realistic throughout much of the state in ARkStorm.

7. Planning for ARkStorm would complement planning for earthquakes. TheShakeOut exercise has become an annual activity in California, with more than 7 million people participating each year. Many of the same emergency preparations are useful for a severe winter storm: laying in emergency food and water, shelter preparations, exercising emergency corporate communications, testing mutual aid agreements, and so on.

CC Sandy Mantoloking NJ NJNG.jpg

Hurricane Sandy Coastal flooding in Mantoloking, N.J., from an Air National Guard helicopter.

Image Credit: New Jersey National Guard/Scott Anema.

2013: Year of expanding FEMA Flood Zones

Hurricane Sandy showed us just how vulnerable our coasts are to hurricanes and sea level rise.

In 2013, FEMA is releasing new, expanded flood zone maps. The maps confirm what we’ve already seen firsthand. Climate Change is making areas that were not prone to flooding 50 or 100 year ago ground zero for the next Sandy, the next Katrina.

CC 20122 12 wx disasters.jpg

Image: Ceres

The concept of “climate resiliency” is now an everyday reality for your insurance company, and for the Governors and residents of New York & New Jersey. And all of us will likely be paying higher rates to cover the increase in “risk” to coastal communities.

Here’s the story from the Yale Forum on Climate Change & Media.

Governor Chris Christie, pragmatic but resolute after months overseeing rebuilding efforts after Superstorm Sandy, has announced that residents in flood-prone areas of New Jersey must elevate their homes or face high insurance premiums under new rebuilding standards.

His guidance? New preliminary flood maps being released by the Federal Emergency Management Agency that will appreciably expand flood zones into new neighborhoods and industrial parks.

Christie’s was a forceful stance, especially coming from a fiscally conservative politician, but it could become the norm across the United States. FEMA is to continue to roll-out updated maps for the whole country through mid-2013 indicating new flood hazards. Many of the maps expand the areas newly falling into 10-and 100-year flood zones.

The broader flood zones mean that owners of many of those properties will likely be forced to buy flood insurance for the first time. For many already having flood insurance, higher premiums are likely.

FEMA’s flood maps include historical flooding as well as recent surge and storm flooding. They don’t include flood risks from projected future sea-level rise. On January 28, new FEMA flood maps for parts of New York City showed that 35,000 buildings and homes have been added to flood zones.

In its reporting on those new flood zone maps, The New York Times wrote that the FEMA action brought news “many New Yorkers were girding for after Hurricane Sandy sloshed away: More areas farther inland are expected to flood. Tidal surges will be more ferocious. And 35,000 more homes and businesses will be located in flood zones, which will almost certainly nudge up insurance rates and determine how some structures are rebuilt.”

The paper reported New York City’s deputy mayor for operations as saying that the new maps will not affect the city’s evacuation zone maps, but that they are predictors for new flood insurance rate maps. That official told the newspaper that the city’s building code will eventually take into account the new maps.

The Times’ Cara Buckley reported also that “far more structures are now in areas where flooding is expected to top three feet,” a level, she reported, that “could easily shove a structure off its foundation.”

She ended her report with this:

“This is going to be very rough on people,” said Chuck Reichenthal, district manager for Brooklyn’s Community Board 13, which includes Coney Island. “Insurance is going to zoom through the roof.”

Climate Cast resources:

Want to know more about climate change? Here are few quick links to credible climate change sources.

-Read the Minnesota Public Radio primer on Climate Change

-NOAA NCDC’s “State of the Climate” report

-AMS Statement on Climate Change

-NASA key evidence of climate change

-Great summary of Modern Day Climate Change from SUNY-Suffolk

-Minnesota Climate Working Group climate change resources

-Mark Seeley’s Weather Talk

-Common climate change myths

-Climate change in the news from Climate Central

-More coverage from The Yale Forum on Climate Change and Media

  • RickA


    I didn’t catch the show, but will listen in the future. I did read the transcript for the Jan. 24th show.

    I was wondering if you had the numbers for the decades of 1900’s, 1910’s, 1920’s and 1930’s.

    I thought it would be interesting to compare the decline in the number of 0 or lower days leading up to the hot 1930’s, and see how that trend compared to the one your spoke about.