Many Californians fear the “Big One,” but it might not be what you think.
It’s not an earthquake. And it isn’t the mega drought. It’s actually the exact opposite.
A new study by Science Advances shows climate change has already doubled the chances of a disastrous flood happening in California in the next four decades. And experts say it would be unlike anything anyone alive today has ever experienced.
Daniel Swain, a climate scientist with UCLA and a researcher involved in the study, describes a megaflood as, “a very severe flood event across a broad region that has the potential to bring catastrophic impacts to society in the areas affected.” He said a megaflood is similar to the 1,000-year flash flood events seen this summer in the St. Louis area and Kentucky, but across a much wider area, such as the entire state of California.
These massive floods, which experts say would turn California’s lowlands into a “vast inland sea,” might have previously happened once in a lifetime in the state. But experts say climate change is increasing the likelihood of these catastrophic disasters, causing them to occur more like every 25 to 50 years.
National Park Service/AP
In this photo provided by the National Park Service, Mud Canyon Road is closed due to flash flooding in Death Valley, California.
Climate change supercharges heavy rain events, making flash floods occur more regularly, as has been noted several times this summer in Eastern Kentucky, St. Louis, and even in California’s Death Valley National Park.
California is prone to these floods from atmospheric rivers naturally, and major floods from them have happened before — but climate change is upping the ante, and millions of people could be impacted.
The study said atmospheric rivers could become consecutive for weeks on end, like seen in this animation. Xingying Huang, one of the authors of the study, made this loop, which illustrates the water vapor transportation and potential precipitation accumulation at selected time slices during the 30-day scenario.
Citizen of the Planet/UCG/Universal Images Group/Getty Images
California's Central Valley, which produces one-fourth of the nation's food, will be ravaged by a megaflood.
The area with the most destruction would be the Central Valley of California, including Sacramento, Fresno and Bakersfield, the study’s authors project. The Central Valley, roughly the size of Vermont and Massachusetts combined, produces a quarter of the nation’s food supply, according to the US Geological Survey.
A flood with the size to fill this valley has the potential to be the most expensive geophysical disaster to date, costing upwards of $1 trillion in losses and devastating the state’s lowland areas, including Los Angeles and Orange counties, according to the study.
That would be more 5 times the cost of Hurricane Katrina, the current costliest disaster in US history.
Mario Tama/Getty Images
Los Angeles and Orange counties could be devastated by a megaflood within the century.
“Such a flood event in modern California would likely exceed the damages from a large magnitude earthquake by a considerable margin,” the study showed.
This study is the first phase of a three-part series studying the effects of a future megaflood event in California. The next two phases are expected to be released in two to three years.
“Ultimately, one of our goals is not just to understand these events scientifically, but it’s also to help California prepare for them,” Swain said. “It’s a question of when rather than if (the megaflood) occurs.”
It’s happened before. It will happen again, but worse, warns scientists
Over 150 years ago, a strong series of atmospheric rivers drenched the Golden State, causing one of the most exceptional floods in history following a dry spell that had left the West parched for decades.
Communities were demolished in minutes.
It was the winter of 1861-1862 and a historic megaflood transformed the San Joaquin and Sacramento valleys into a “temporary but vast inland sea,” according to the study. Some areas had up to 30 feet of water for weeks, obliterating infrastructure, farmland, and towns.
Sacramento Public Library
This 1861 photograph shows flooding in Sacramento.
Sacramento, the new state capital at the time, was under ten feet of debris-filled water for months.
The catastrophe began in December 1861, when nearly 15 feet of snow fell in the Sierra Nevada. Repetitive atmospheric rivers dropped warm rain for 43 days thereafter, dumping water down the mountainous slopes and into the valleys.
Four thousand people lost their lives, one-third of the state’s property was destroyed, a quarter of California’s cattle population drowned or starved, and one in eight homes were a complete loss by floodwaters.
In addition, one-fourth of California’s economy was obliterated, resulting in a state-wide bankruptcy.
Swain warns a megaflood like this will happen again, but worse and more frequent.
Melina Mara/The Washington Post/Getty Images
Downtown Sacramento today, which was raised 10-15 feet after the historic floods.
“We find that climate change has already increased the risk of a (1862) megaflood scenario in California, but that future climate warming will likely bring about even sharper risk increases,” the study warns.
Many of today’s major cities with millions of residents are built directly on top of the ancient flood deposits, Swain added, putting far more people in harm’s way.
About 500,000 people lived in California in 1862. Now, the state’s population is over 39 million.
“When this (flood) occurs again, the consequences would be wildly different than they were back in the 1860s,” Swain said.
Climate change increases the amount of rain the atmosphere can hold and causes more water in the air to fall as rain, which can lead to immediate flooding. Both are and will continue to occur in California.
The new study shows a rapid increase in the likelihood of week-long, recurring strong-to-extreme atmospheric rivers during the cool season. An atmospheric river is a long, narrow region of heavy moisture in the atmosphere that can transport moisture thousands of miles, like a fire hose in the sky. They usually bring beneficial rainfall to drought-prone regions like California but could quickly become hazardous with a warming climate.
Historically these winter atmospheric rivers dump feet of snow in the Sierra Nevada, but as climate warms, more of the snow will fall as rain. Instead of melting slowly over time, it all runs off, piles up, and floods immediately.
With a neighbor like the Pacific Ocean, California has “an infinite reservoir of water vapor offshore,” Swain added.
California’s mountainous terrain and wildfire risk make it especially vulnerable to flooding. Lingering burn scars from wildfires can create a steep, slick surface for water and debris to flow off. With wildfires becoming larger and burning more area thanks to climate change, more areas are susceptible to these debris flows.
Although models show this megaflood is inevitable, experts say there are ways to mitigate excessive loss.
“I think the extent of (megaflood) losses can be significantly reduced by doing certain sorts of things to revamp our flood management and our water management systems and our disaster preparedness,” Swain said.
Huang, a project scientist at the National Center for Atmospheric Research and a researcher involved in the study, said everyone can make a small effort in combating climate change.
“If we work together to decrease future emissions, we can also reduce the risk of extreme events,” Huang said.
ccpixx photography // Shutterstock
Climate scientists continue to prove the link between climate change and extreme weather events, from hurricanes to droughts to floods. With each new weather event comes the potential for damage to people’s homes and possessions. This is not just emotionally damaging and physically dangerous, but also comes with a steep associated financial cost.
To discover how climate-resilient construction can help to mitigate natural disasters, Stacker first determined the economic damage within the United States caused by eight types of natural disasters between 2010 and 2020, based on data compiled by Our World In Data. Economic damage data spanning 2010–20, provided by EM-DAT, is expressed as a portion of U.S. gross domestic product (GDP), provided by the World Bank.
Fortunately, some of these costs can be avoided with climate-resilient construction to mitigate natural disasters. In order to understand how different natural disasters can be better anticipated and mitigated through building strategy, we outlined various climate-resilient construction and projects being used to minimize the effects of those disasters using data from the U.S. government, design firms, and media outlets. Choosing the building location carefully and with advice from experts, universally, can help mitigate many of these natural disasters.
You may also like: Space discoveries that will blow your mind
Deni_Sugandi // Shutterstock
- Economic damages between 2010–20: 0.0002% of GDP
If you live near an active volcano, evacuating remains the most important safety measure when warned of a potential eruption. However, there are ways to construct a building to make it more resilient in the face of a volcanic eruption. As eruptions can whip up fierce winds, mostly flat roofs with a slight, 15-degree slope will be less likely to be hit by the wind. The slope will allow ash to slide off the roof. Triple roof support and using smooth materials for roofing will also help ash slide away.
Similarly, concrete structures’ natural wind resistance fares better than timber-framed buildings. Lastly, designing simpler architectural structures will leave less room for ash to settle, creating a safer environment.
- Economic damages between 2010–20: 0.0004% of GDP
Following proper land-use procedures will help mitigate the impacts of landslides on your property. These procedures include avoiding building near steep slopes, close to the edges of mountains, along natural erosion valleys, and near drainage ways. The use of sandbags and retaining walls are techniques that can protect buildings from floodwaters and mud caused by landslides. In areas prone to mud and debris flow, build channels or deflection walls to redirect the flow of debris around the structure—but be sure not to direct it into someone else’s building.
In 2005, a landslide destroyed 19 homes and forced the evacuation of more than 300 homes in Bluebird Canyon in Laguna Beach, California, leading to a 2.5-year reconstruction project using clever building strategies. Beyond smarter architecture, drainage systems were installed and edges along the land were stabilized to protect against another disaster. Consulting with a geotechnical professional before building will help mitigate further damage as well.
Kurniawan Rizqi // Shutterstock
- Economic damages between 2010–20: 0.0005% of GDP
When working on a building resilient to earthquake damage, be sure to include base isolators. Conventional buildings will shake with the ground during an earthquake, and when they shake too much, structural elements can sustain heavy damage, sometimes to the point of destruction.
Base isolators act as shock absorbers between the building and the moving ground. This lets the building slide back and forth instead of shaking during an earthquake, so it will still remain upright. Layers of steel and rubber with a lead core built between the floor and the foundation will also help to isolate the building from ground motion. Steel plate wall systems can mitigate earthquake damage as well.
The Ritz-Carlton/JW Marriott hotel building in Los Angeles is the first to use an advanced steel plate shear wall system to resist earthquakes. At 54 stories tall, the hotel must be able to withstand earthquakes.
G B Hart // Shutterstock
- Economic damages between 2010–20: 0.0015% of GDP
There are a number of ways to make your home more resilient to extreme heat caused by climate change. In order to keep heat out, cover windows with drapes or shades and weather-strip windows and doors. Insulation will help keep the heat out, and window reflectors can help by reflecting heat back outside.
When possible, install window air conditioners to cool the house or building and insulate around them, so the cool air doesn’t escape and the hot air doesn’t come in. For those unable to afford the costs associated with adding these climate-resilient measures, the Low Income Home Energy Assistance Program (LIHEAP) can provide financial support.
For new constructions, passive houses may be the solution to beat increasing global temperatures. A type of housing that dates back centuries, passive houses rely on building walls, roofs, and windows with more insulation and seals, including triple-paned windows, highly insulated wall systems, and energy-efficient heat pumps. Implementing these architectural elements leads to a nearly air-tight building, reducing the amount of hot air that can enter.
Piyawat Nandeenopparit // Shutterstock
- Economic damages between 2010–20: 0.0225% of GDP
To prevent or reduce damage from flooding, there are a few elements that must be taken into account when designing a building or home. Preventing water ingress will ensure a safer structure. Constructing the building with concrete or steel with concrete protects against water entering—as both of these materials are more impervious to flooding than other materials.
Installing raised windows, doors with materials to prevent water damage, and floor guards can also protect the structure. Finally, it’s important to have a drainage system in place in case water does get in, which could be sub-floor drainage, sump pumps, and non-return valves.
You may also like: How communities are dealing with invasive species across the U.S.
Christian Roberts-Olsen // Shutterstock
- Economic damages between 2010–20: 0.0233% of GDP
When constructing buildings and homes to avoid wildfires, choosing the right location is crucial. Ideally, construction wouldn’t take place in any danger zones, but that’s not always possible. It’s important to consider the climate, wind patterns, vegetation, and escape routes when choosing where to build.
Consider the structure itself—for example, patios are more resilient than decks. Typically, patios are made from non-flammable materials whereas decks are made from wood and can trap vegetation beneath them, which act as fuel. For similar reasons, slab-on-grade and full basement foundations provide more protection as opposed to pier foundations or crawl spaces, where vegetation and other flammable debris can accumulate. Building a house from concrete and other masonry materials provide the greatest protection from fire, and insulated windows contribute even more to architectural resilience.
nvelichko // Shutterstock
- Economic damages between 2010–20: 0.024% of GDP
Buildings must be designed as a source of water to be resilient to drought. The type of water that can be produced or collected from a building include graywater, blackwater, rainwater, stormwater, or foundation drainage.
Graywater is the leftover water collected from showers, washing machines, and bathroom sinks, and it’s the cleanest kind of water that could be collected from a building. While it is not potable water, graywater can be used for irrigation, laundry, and for flushing toilets. This makes it so potable water does not have to be used for those purposes. In San Francisco, the capture and reuse of this non-potable water is mandated for new buildings.
FotoKina // Shutterstock
- Economic damages between 2010–20: 0.2313% of GDP
Residences continue to be built and bought close to oceans, in spite of the rising sea levels and increasing storms caused by climate change. To make these homes more resilient in the face of storms, there are a number of techniques that builders and designers can use.
For example, when homes are round they are more aerodynamic, deflecting airflow around the structure instead of absorbing the force. These round buildings get 30% less pressure building around them than a conventionally shaped home. The use of high-quality materials plays a big role as well—materials such as plywood and metal—and roofs should be anchored well so they don’t fly off. The elevation is important, too: Deltec Homes, a company that builds storm-resilient homes, recommends building at least 2 feet above flood surge.
While all these tips are important, when storms are bad enough and evacuation orders go into effect, the most important thing is still to listen to that guidance and evacuate.
Roger Brown Photography // Shutterstock
In the 18 months since the coronavirus first hit the United States, an almost infinite number of things have changed. Among them is the way people in the country respond to emergencies and natural disasters.
In some ways, these changes have been for the better. For example, local governments, fire departments, law enforcement agencies, and hospitals are now working with the private sector to enhance response efforts. This means people in need or in danger get assistance much quicker than in the past. Additionally, important information is disseminated much faster, allowing communities to respond in more helpful and meaningful ways.
On the other hand, the pandemic has caused many potential disaster resources to shut down. Agencies that would have provided relief or buildings that may have acted as hurricane or tornado shelters are no longer open. This means individuals need to be more prepared than ever should a disaster hit their area.
Valley Food Storage consulted the Federal Emergency Management Agency’s list of disasters and emergencies and selected key ways to stay prepared for a variety of emergency scenarios. Using information from government organizations like FEMA, the Ready Campaign, the Centers for Disease Control and Prevention, and the Red Cross, dozens of steps to ensure you and your loved ones are safe should anything from a power outage to a nuclear explosion hit your area have been compiled.
David Pereiras // Shutterstock
Earthquakes, the violent and sudden shaking of the ground, are caused by the breaking and shifting of subterranean rock. Each of the 50 states is at some risk of an earthquake, though the West Coast is considered at higher risk than the rest of the country, as the area is situated on the boundary of major tectonic plates. The IRIS Consortium reports that mid-level earthquakes occur about 20 times per year, but that massive quakes, like the 1964 9.2 magnitude quake that occurred in Prince William Sound, Alaska, are much rarer. The Ready campaign suggests that folks who live in high-risk areas always be prepared for a quake by having ready kits—containing food, water, portable chargers, first aid supplies, sanitary supplies, and a whistle—in their homes, offices, and cars. Assessing your home’s structure, making necessary repairs, and securing all furniture and decorative objects are other ways to ensure potential damage is limited.
Margarita Young // Shutterstock
Extreme heat is a period of high heat—above 90 F—and humidity that lasts for a period of two to three days or longer. It is the most common and dangerous extreme weather event we experience in the United States and is responsible for the highest number of weather-related deaths each year.
Prepare for extreme heat by ensuring that you’re properly hydrated and have plenty of fluids on hand—at least three-quarters of a gallon per person—for all members of your household. Cover your windows and glass doors with curtains or window reflectors to keep the heat from seeping into your house, and have backup cooling options available should your air conditioner fail. Fans and local cooling centers are good examples. Finally, know the signs for heat-related illnesses like heat stroke and heat exhaustion, and be prepared to reach out to your medical providers if necessary.
Monkey Business Images // Shutterstock
As with earthquakes, every state in the United States is subject to flooding at any given time. This type of natural disaster is the most concerning as floods are the most frequent and costly weather event and seldom come with much warning, happening in as quickly as a few minutes. As a result, it is essential that you be prepared for a possible flood at all times, especially during rainy seasons. The best ways to do this are by purchasing flood insurance, preparing emergency kits with nonperishable food, bottled drinking water, and sanitary supplies, and ensuring all essential documents are stored in an easy-to-find, waterproof container. Homeowners should also bring in or tie down all outdoor furniture and turn off any propane tanks that may be on their property. If there is time between the issuing of a flood warning and the event itself, unplug any appliances in order to avoid a power surge, and move all valuables to higher ground to ensure their safety.
Lisa F. Young // Shutterstock
Primarily affecting Gulf Coast and Southern Atlantic seaboard states, hurricanes are massive storm systems that form over the ocean and move onto land, bringing high winds, heavy rain, flooding, and tornadoes. Typically, hurricane season annually runs from June 1 through Nov. 30, though the Centers for Disease Control and Prevention suggests all individuals who live within these hurricane zones be prepared well in advance of that time period. To prepare for these inevitable storms, sign up for notification services, have tested evacuation plans in place, prepare necessary go bags—with everything from clothes to shelf-stable food and water to medications—and round up important documents, as suggested by the Ready Campaign. Homeowners should also ensure that their insurance is up to date and that their properties are protected by installing sewer backflow valves, cataloging belongings, and anchoring fuel and propane tanks.
Hanna Taniukevich // Shutterstock
While landslides aren’t as common as many of the other emergencies on this list, they do happen, typically in the aftermath of other major weather events such as hurricanes, flooding, heavy snowfall, earthquakes, and volcanic eruptions. Risk factor increases not by where in the country you live, but by the type of terrain on which you live—folks who live at the top or base of slopes, in areas frequently affected by forest fire, or in areas where landslides have happened in the past are more likely to experience this type of disaster. The best way to prepare for coping with a landslide is to know your risk. An assessment of your property or location by a qualified geotechnical professional can be invaluable, as can following proper land usage procedures. Other solid ways to be ready for a potential landslide include subscribing to community warning systems, protecting your property by building channels or deflection walls to help direct debris flow, and having an evacuation plan in place should the need arise for one.
Studio MDF // Shutterstock
While the United States has never experienced a nuclear attack via a nuclear weapon on home soil, the risk level is currently at a historic high. Six major cities—including New York, Chicago, Houston, Los Angeles, San Francisco, and Washington D.C.—are the most likely target of a potential attack, according to Irwin Redlener, a Columbia University public-health expert. When preparing for a potential nuclear attack in one of these major cities or for a radiation emergency anywhere in the country, there are a few things you can do. First, identify a suitable shelter, ideally a location underground or in the middle of a building made of concrete or bricks. Second, put together an emergency go-kit that contains the basic necessities like food, water, first aid supplies, and sanitizing equipment. Finally, identify and subscribe to notification and information systems if possible.
Perry Correll // Shutterstock
Power outages can happen for a number of reasons, from extreme heat or cold to heavy storms to equipment failure. These events can be incredibly tricky because there is no way of knowing how long they may last, and they impact almost every area of our lives from communication to access to water to transportation. If you live in an area where power outages are common, such as a major city where the grid is often overwhelmed or a rural area that sees a lot of storms, prepare by taking stock of the items needed that require electricity. Come up with backup power plans for these appliances, like a generator, and ensure you have enough flashlights and batteries for all household members. Food and fresh water are a major concern during power outages, so be well-equipped with enough shelf-stable food and bottled water to last for several days.
According to the National Severe Thunderstorms Laboratory, the United States sees about 100,000 thunderstorms each year. Of these storms, 10% are severe, meaning they contain hail 1-inch or larger, wind above 57 mph, or a tornado. These thunderstorms happen most often in the spring and summer months, though they are possible year-round. To prepare for these events, install surge protectors or a lightning rod, cut down trees that may fall on your home, and tie down or move all outdoor furniture inside. It would also be wise to have an emergency kit on hand similar to those used in case of a power outage or earthquake, which contains food, water, medical supplies, sanitization equipment, and necessary medicines.
Noel V. Baebler // Shutterstock
Tornadoes are most common in the Great Plains, or center region, of the United States. In particular, tornado alley—which includes the states of Texas, Oklahoma, Kansas, Nebraska, South Dakota, and North Dakota—sees a lot of action with some areas getting up to nine tornadoes a year. If you live in this region of the country, it is absolutely essential that you have an emergency plan in place that includes possible shelter locations. Additionally, a well-stocked emergency kit is a necessity, as is a subscription to a community warning service. With more than 1,000 tornadoes touching down in the United States each year, it’s likely that Midwesterners will experience at least one in their lifetime, so taking a few moments to prepare now could save a lot of heartache in the future.
Roger Brown Photography // Shutterstock
The American Geosciences Institute reports that there are 169 active volcanoes in the United States. The vast majority of them are in Alaska, though there are others in Hawaii, Washington, Oregon, California, Idaho, Nevada, Utah, Arizona, New Mexico, Colorado, and Wyoming. The primary concern when it comes to a possible eruption is ash, as it can travel for miles and can be incredibly dangerous to inhale. Those who live in a danger zone can prepare by having a shelter-in-place plan ready, which includes all the necessary supplies needed to remain inside for a number of days. Along with the standard items like food, water, and medicine, masks and safety goggles—that could keep ash from entering your eyes, nose, and mouth—would also be important to include. Those who live in a lava-flow zone should have all the same equipment, but an evacuation plan instead of a shelter-in-place plan.
Peter Galleghan // Shutterstock
Despite what news coverage may lead you to believe, the Congressional Research Service reports that more wildfires occur in the eastern half of the country than in the western half. That being said, fires on the West Coast are larger and burn for longer, making them both more dangerous and more damaging. Regardless of what state you call home, having a wildfire emergency plan in place is a good idea. Sign up for local warnings, know your evacuation zone, and have essential items—including masks to protect you from smoke inhalation ready to go during peak wildfire season, which is typically late May to early October. Prepare your property for potential burn. Use fire-resistant materials when building, ensure you have an outdoor water source with a working hose to put out small flames, and create a fire-resistant zone free of leaves and debris 30-feet or more from your home.
VanoVasaio // Shutterstock
The Northeast and Upper Midwest are famous for their frigid winters—daily temperatures in these areas hover between 19 F and 32 F during the colder months. Add snow and sleet into the mix, and these areas of the country are prime locations for winter storms. Winter storms can bring a loss of power, dangerous or impossible traveling conditions, and increased risk of hypothermia, frostbite, and car accidents. The good news about winter storms is that there’s generally ample warning. Unlike an erupting volcano, for example, you typically know about a storm 24-48 hours before it hits. This should provide time to do things like ensure you have plenty of supplies if you need to shelter in place, nab a backup generator, and bring any pets and cars under cover. Before the winter season hits, weatherproof your home by trimming any trees that could be felled by snow or high winds, insulate water lines and walls, and install storm-proof windows.
SeaRick1 // Shutterstock
In 2020, the FBI designated 40 shootings as active shooter incidents, a 100% increase from 2016. These attacks are on the rise and are likely to remain that way for as long as gun control laws remain lax. Because active shooter situations are generally random, there is really no good way to prepare for a possible attack, aside from knowing how to respond. The FBI recommends a “run, hide, fight” strategy. If you find yourself in the vicinity of an active shooter, your first and best option is to evacuate the area, leaving behind all nonessential items such as purses and cellphones. If evacuating is not possible, find a place to hide where the shooter may not find you, like a closet or behind a table. As a last resort—and only if your life is in danger—fight back, throwing items at the shooter or yelling to throw the attacker off focus.
Rawpixel.com // Shutterstock
Many experts believe that cyberattacks are poised to be a new brand of warfare. Rather than shooting guns or throwing hand grenades, countries will attack each other by compromising computer systems, essentially knocking down large parts of their infrastructure. Should a cyberattack of that size happen, there might not be much you can do to protect yourself on an individual level. However, there are a plethora of ways you can prepare for smaller-scale cyberattacks including keeping antivirus software updated, regularly backing up your files, and protecting your home network connection. Using hard-to-guess passwords and two-factor authentication methods are also great ways to ensure your private information remains private.
Pavel Chepelev // Shutterstock
Explosions are another type of emergency that are incredibly hard to prepare for as you never really know where or when one may happen. The best advice the Ready campaign has to offer is to have emergency kits on hand both at home and in your car, which include medical supplies, sanitizing supplies, and masks to protect from particles and dust, and to have a list of places you could shelter should that be necessary. Knowing how to identify a suspicious package or letter could also save you from becoming the victim of an explosion. Look for packages that aren’t addressed to a specific recipient, have excessive postage, or have protruding wires and report them to the police immediately.
This story originally appeared on Valley Food Storage and was produced and distributed in partnership with Stacker Studio.