ARkStorm
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The ARkStorm (for
Atmospheric River An atmospheric river (AR) is a narrow corridor or filament of concentrated moisture in the atmosphere. Other names for this phenomenon are tropical plume, tropical connection, moisture plume, water vapor surge, and cloud band. Atmospheric rivers ...
1,000) is a hypothetical megastorm, whose proposal is based on repeated historical occurrences of atmospheric rivers and other major rain events first developed and published by the Multi-Hazards Demonstration Project (MHDP) of the
United States Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on Mar ...
(USGS) in 2010. An updated model was published as ARkStorm 2.0 in 2022.


ARkStorm 1.0 (2010 Study)

The ARkStorm 1.0 scenario describes an extreme storm that devastates much of
California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
, causing up to $725 billion in losses (mostly due to flooding and erosion), and affecting a quarter of California's homes. The scenario projects impacts of a storm that would be significantly less intense (25 days of rain) than the California storms that occurred between December 1861 and January 1862 (43 days). That event dumped nearly of rain in parts of California. USGS sediment research in the San Francisco Bay Area, Santa Barbara Basin, Sacramento Valley, and the Klamath Mountain region found that "megastorms" have occurred in the years: 212, 440, 603, 1029, , 1418,
1605 Events January–March * January 1 – William Shakespeare's play ''A Midsummer Night's Dream'', copyrighted 1600, is given its earliest recorded performance, and witnessed by the Viscount Dorchester. * January 7 – Shakespeare's play ' ...
, 1750, 1810, and, most recently, 1861–1862. Based on the intervals of these known occurrences, ranging from 51 to 426 years, for a historic recurrence of, on average, every 100–200 years. Geologic evidence indicates that several of the previous events were more intense than the one in 1861–1862, particularly those in 440, 1418, 1605, and 1750, each of which deposited a layer of silt in the Santa Barbara Basin more than one inch (2.5 cm) thick. The largest event was the one in 1605, which left a layer of silt two inches (5 cm) thick, indicating that this flood was at least 50% more powerful than any of the others recorded.


Description

The conditions built into the scenario are "two super-strong atmospheric rivers, just four days apart, one in Northern California and one in Southern California, and one of them stalled for an extra day". The ARkStorm 1.0 scenario would have the following effects: * The Central Valley would experience
flooding A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant concern in agriculture, civi ...
long and at least wide. * Serious flooding also would occur in Orange County,
Los Angeles County Los Angeles County, officially the County of Los Angeles and sometimes abbreviated as LA County, is the most populous county in the United States, with 9,663,345 residents estimated in 2023. Its population is greater than that of 40 individua ...
,
San Diego San Diego ( , ) is a city on the Pacific coast of Southern California, adjacent to the Mexico–United States border. With a population of over 1.4 million, it is the List of United States cities by population, eighth-most populous city in t ...
, the
San Francisco Bay area The San Francisco Bay Area, commonly known as the Bay Area, is a List of regions of California, region of California surrounding and including San Francisco Bay, and anchored by the cities of Oakland, San Francisco, and San Jose, California, S ...
, and other coastal communities. * Wind speeds in some places would reach . * Hundreds of
landslides Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslide ...
would damage roads, highways, and homes. * Property damage would exceed $300 billion, most from flooding. * Demand surge (an increase in labor rates and other repair costs after major natural disasters) could increase property losses by 20 percent. * Agricultural losses and other costs to repair lifelines, drain flooded islands, and repair damage from landslides, could bring the total direct property loss to nearly $400 billion. * Power, water, sewer, and other lifelines would experience damage that could take weeks or months to restore. * Up to 1.5 million residents in the inland region and delta counties would need to evacuate due to flooding. * Business interruption costs could reach $325 billion, in addition to the $400 billion required for property repair costs, meaning that an ARkStorm scenario is projected to cost $750 billion (~$1 trillion in 2022 dollars), nearly three times the amount of damage predicted by the next "Big One", a hypothetical
Southern California Southern California (commonly shortened to SoCal) is a geographic and Cultural area, cultural List of regions of California, region that generally comprises the southern portion of the U.S. state of California. Its densely populated coastal reg ...
earthquake with roughly the same annual occurrence probability.


ARkStorm 2.0 (2022 update)

This update, with parts of the research on impacts still ongoing, has examined how climate change is expected to increase the risk of severe flooding from a hypothetical ARkStorm, with runoff 200% to 400% above historical values for the
Sierra Nevada The Sierra Nevada ( ) is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primari ...
in part due to a decrease in the portion of precipitation that falls as snow, as well as an increase in the amount of water that storms can carry. The likelihood of the event outlined in the ARkStorm scenario is now once every 25–50 years, with projected economic losses of over $1 trillion (or more than five times that of
Hurricane Katrina Hurricane Katrina was a powerful, devastating and historic tropical cyclone that caused 1,392 fatalities and damages estimated at $125 billion in late August 2005, particularly in the city of New Orleans and its surrounding area. ...
).


Implications

Current flood maps in the U.S. rarely take recent projections from projects like ARkStorm into account, especially FEMA's maps, which many decision-makers have relied on. Land owners, flood insurers, governments and media outlets often use maps like FEMA's that still fail to represent many significant risks due to: 1) using only historical data (instead of incorporating climate change models), 2) the omission of heavy rainfall events, and 3) lack of modeling of flooding in urban areas. More robust and up-to-date models, like the First Street Foundation's riskfactor.com, should better represent true flood risk though it is unclear if that model, for example, incorporates any ARkStorm science. Government agencies may decide how much risk to accept, and how much risk to mitigate. The Netherlands' approach to flood control, for example, plans for 1 in 10,000 year events in heavily-populated areas and 1 in 4,000 year events in less well-populated areas.


See also

*
Extreme weather Extreme weather includes unexpected, unusual, severe weather, severe, or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past. Extreme events are based on a location's recorded weat ...
* Lists of floods in the United States * North American Monsoon * Pineapple Express * The Big One (earthquake)


References


External links


USGS Multi-Hazards Demonstration Project: ARkStorm: West Coast Storm Scenario
(including video)
USGS Newsroom: ARkStorm: California's other "Big One"


* ttp://www.hcn.org/issues/42.3/the-other-big-one High Country News: The other Big One, Judith Lewis
Water Education Foundation, Mar-Apr 2011: Plausible and Inevitable: The ARkStorm Scenario, by Gary Pitzer

''Megastorms Could Drown Massive Portions of California''
January 5, 2012 ''
Scientific American ''Scientific American'', informally abbreviated ''SciAm'' or sometimes ''SA'', is an American popular science magazine. Many scientists, including Albert Einstein and Nikola Tesla, have contributed articles to it, with more than 150 Nobel Pri ...
'' * * {{Natural disasters Environment of California Natural disasters in California Weather hazards Storm