通常与西海岸相关的灾难包括毁灭性的地震和失控野火但是有一场比这两种情况都糟糕得多的大灾难，而且随时都有可能发生。
官员和专家称之为“方舟风暴”，这是另一个很少有人谈论的“大风暴”。
随着加州2020年雨季的到来，想象一下整个西海岸一个月的暴雨。
该州将被10到20英尺的雨水淹没。
在一些地方高达200英寸，洪水几乎会袭击该州的每个主要人口中心。
巨大的降雨量意味着旧金山湾区、洛杉矶、圣地亚哥和萨克拉门托的部分地区都将被淹没在水下。这将导致数以千计的山体滑坡、大坝坍塌，并摧毁该州的整个农业。
这可能听起来像是一部后世界末日电影中的场景，但这种类型的风暴不仅是可能的，它以前也发生过。
加州有史以来最致命和破坏性最大的自然灾害，即所谓的“特大风暴”，在1861年和1862年冬天袭击了该州。
“我家是19世纪70年代来到加州的。真正最大的风暴是19世纪60年代，我从未听说过，”露西·琼斯博士告诉美国广播公司新闻。
琼斯作为地震学家在美国地质调查局工作了33年，她一生中的大部分时间都在帮助社区和领导人为不可避免的灾难做准备。
1861年和1862年的致命风暴从根本上改变了加利福尼亚。
“洪水淹没了加利福尼亚四分之一的房屋。...那一年，它摧毁了加州三分之一的应税土地，并使该州破产，”琼斯说。
情况太糟糕了，该州不得不暂时将首都从萨克拉门托移走。
加州大学洛杉矶分校气候科学家丹尼尔·斯温(Daniel Swain)说:“这是一场持续数周的极端降水和洪水事件，基本上用洪水填满了中央山谷的大部分，形成了一片内陆海，据称宽40英里，长150英里。”
斯温认为，该州40万人中大约有1%死亡，但官方没有伤亡人数。
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琼斯和斯温已经敲响了大约十年的警钟，如果今天发生类似的风暴会发生什么。
“我们做的模型叫做‘方舟风暴’。实际上雨下了大约25天。这足以淹没加州四分之一的房产，”琼斯说。
九年前公布的模型是对地方和国家领导人的一个警告，警告他们有一天这种情景会成为现实。
“这是一场我们正在谈论的万亿美元类型的灾难。因此，就加州的长期后果而言，这是一个非常高的水平，”斯温说。
该模型预测“大量生命损失”，至少150万加州人将不得不从家中撤离。
加州紧急服务办公室花了数年时间制定“特大风暴”计划
“洪水风险对我们来说并不陌生。加州有很长的洪水泛滥的历史，”加州OES的副主任蒂娜·库里告诉美国广播公司新闻。
该州四分之一的建筑可能会发生洪水，其影响尤其灾难性，因为只有12%的加州财产投保洪水。
库里说:“个人需要知道他们的风险是什么，知道你住在哪里，并为你的家人制定一个计划来管理紧急情况，并能够从当地领导那里得到指示。”
琼斯和斯温警告说，像这样的风暴不是反常事件，而是不可避免的。
树木年轮和岩石显示，在过去的1800年里，有六次“特大风暴”比1861-1862年的风暴更加严重。
斯温说，最近的证据表明，“大风暴”大约每200年发生一次，这意味着理论上下一次“大风暴”可能在未来40年的任何时候发生。
不像地震在美国和野火期间，预测一场大规模的降雨事件要稍微容易一些，但准备工作更具挑战性。
“从很多方面来说，准备都非常困难，你可以说，我们让事情变得更糟了，因为我们投入了洪水控制，然后我们在洪水控制之下进行建设。琼斯告诉美国广播公司新闻:“因此，我们有许多房屋坐落在防洪堤保护的洪泛区。”。
保护这些房屋的防洪堤是为75年一遇的洪水而设计的，而不是一场“大风暴”。
由于气候变化，下一场“大风暴”可能会有多糟糕，什么时候会发生。
科学家警告说，最初的ARkStorm模拟是一个谨慎的场景;下一场“大风暴”的现实可能会更糟糕。
斯温和他的团队正在研究一种新的方舟风暴模拟。“我们现在有点忙;他说:“我们已经准备好进行一些模拟，并开始启动。
2011年的原始模型没有考虑气候变化，斯温说，这可能会使下一次方舟风暴比1861年和1862年的洪水更糟糕，比每200年更频繁。
Cal OES现在在所有的灾难计划中都考虑到了气候变化。库里告诉美国广播公司新闻，“我们已经做了大量工作来考虑气候变化对所有这些的影响”。
如果今天加州1%的人口死于一场新的暴风雪，那么大约有395，000人——这无疑是美国历史上最严重的自然灾害。
这2017年2月奥罗维尔大坝恐慌-当180，000人因担心它会倒塌而被疏散时-是紧急计划的警钟。库里说:“包括奥罗维尔在内的每一个活动都是一个机会，让我们反思我们已经计划好了什么，实际发生了什么，并做出改进。”
几天的降雨几乎导致老化的大坝基础设施完全失效，斯温说这可能会释放出“30英尺的水墙”。
斯温说，一场万亿美元的方舟风暴灾难也可能使整个政府陷入更深的债务之中，并削弱该州的农业、旅游业和娱乐业。
由于加州种植了我国的大部分农作物，其影响将波及整个国家。
琼斯说，规划这些类型的长期灾害是政府的一项关键责任。
她说:“这是政府的职责之一，这是一个挑战，因为政治家(在任)时间很短，因为他们是当选的。”。“但政府需要为我们做的是成为未来的担保人。”
“这并不一定是可怕的事情，”库里说。“如果你有信息，如果你有计划和准备所需的工具，那么我们可以做很多事情来保护加州的安全。”
California's 'trillion dollar' mega disaster no one is talking about
Disasters typically associated with the West Coast include devastatingearthquakesand out-of-controlwildfires, but there's an epic disaster that could be far worse than both -- and it could happen at any point.
Officials and experts call it the "ARkStorm," and it is the other "big one" few are talking about.
With California's 2020 rainy season now underway, imagine almost a month of drenching storms along the entire West Coast.
The state would be swallowed in 10 to 20 feet of rain.
At up to 200 inches in some places, floods would hit nearly every major population center in the state.
The sheer amount of rain means parts of the San Francisco Bay area, Los Angeles, San Diego and Sacramento would all be underwater. It would cause thousands of landslides, major dam failures and decimate the state's entire agriculture industry.
It might sound like a scene from a post apocalyptic movie, but this type of storm is not only possible, it's happened before.
California's deadliest and most-destructive natural disaster in recorded history, a so-called "mega storm," hit the state in the winter of 1861 and 1862.
"My family came to California in the 1870s. And the really biggest storm was the 1860s, and I had never heard of it," Dr. Lucy Jones told ABC News.
Jones worked as a seismologist at the U.S. Geological Survey for 33 years and has spent the better part of her life helping communities and leaders prepare for inevitable disasters.
The deadly storm of 1861 and 1862 fundamentally changed California.
"The flood flooded a quarter of the homes in California. ... It destroyed one-third of the taxable land of California in that year, and it bankrupted the state," Jones said.
It was so bad the state had to temporarily move the capital away from Sacramento.
"This was a multiweek, extreme precipitation and flood event that essentially filled up a significant portion of the Central Valley with flood water, creating an inland sea, supposedly 40 miles wide and 150 miles long," UCLA Climate Scientist Daniel Swain said.
Swain believes roughly 1% of the state's 400,000 people died -- but there is no official number of casualties.
Jones and Swain have been sounding the alarm for about a decade about what could happen if a similar storm happened today.
"Our model that we did we called the ARkStorm. It was actually raining for about 25 days. And that was enough to flood one-quarter of the property in California," Jones said.
The model published nine years ago serves as a warning to local and national leaders about a scenario that will become reality one day.
"This is very much a trillion dollar-type disaster that we're talking about. So this is on a really high level, in terms of what the long-term consequences would be from California," Swain said.
The model predicts "substantial loss of life" and at least 1.5 million Californians would have to be evacuated from their homes.
California's Office of Emergency Services has spent years developing plans for "mega storms."
"Flood risk is not something that was an unknown to us. California has a long history of widespread floods," Tina Curry, the deputy director of Cal OES, told ABC News.
A quarter of the buildings in the state could flood, with the impact especially catastrophic as only 12% of California property is insured for flooding.
"Individuals need to know what their risks are, know where you live and and have a plan for your family to manage an emergency and be able to get the instructions from your local leadership," Curry said.
Jones and Swain warned that a storm like this is not a freak event -- it is inevitable.
Tree rings and rocks show six "mega storms" more severe than the 1861-1862 storm in the last 1,800 years.
Swain said recent evidence suggests a "mega storm" happens about once every 200 years, meaning in theory the next "big one" could happen at any point in the next 40 years.
Unlikeearthquakes and wildfires, it is a little easier to predict a massive rain event, but more challenging to prepare.
"It's very difficult to prepare in many ways, and we have, you can argue, that we've made it worse, because we put in our flood control, and then we built underneath the flood control. So we have a lot of homes sitting in floodplains protected by levees," Jones told ABC News.
The levees protecting those homes are designed for a 75-year flood event, not a "mega storm."
And how bad the next "mega storm" might be, and when it might take place, is in flux because of climate change.
Scientists warn the initial ARkStorm simulation is a cautious scenario; the reality of the next "mega storm" could be far worse.
Swain and his team are working on a new ARkStorm simulation. "We're sort of in the thick of it right now; we're ready to press go on some of these simulations and get cranking," he said.
The original model from 2011 did not take climate change into account, something Swain said could make the next ARkStorm even worse than the flood of 1861 and 1862 and more frequent than every 200 years.
Cal OES is now taking climate change into account in all of its planning for disasters. "We absolutely have done a lot of work to consider the effects of climate change on all of this," Curry told ABC News.
If 1% of California's population died today as a result of a new ARkStorm that would be roughly 395,000 people -- easily the worst natural disaster in U.S. history.
TheFebruary 2017 Oroville Dam scare-- when 180,000 people were evacuated due to fears it would collapse -- was a wakeup call for emergency planning. "Every event, including Oroville, is an opportunity to reflect on what we've had planned for, what actually happened and make improvements," Curry said.
The days of rain nearly caused the aging dam infrastructure to fully fail, which Swain said would have likely unleashed a "30-foot wall of water."
A trillion-dollar ARkStorm disaster could also send the entire government deeper into debt, and cripple the state's agriculture, tourism and entertainment industries, according to Swain.
Since California grows a majority of our country's crops, the impact would be felt across the entire country.
Planning for these types of long-term disasters is a key responsibility of government, Jones said.
"That's one of the roles of government, and it's a challenge because politicians are [in office for] very short timeframes, because they're elected," she said. "But what government needs to be doing for us is being the guarantor of the future."
"It's not something that has to be scary necessarily," Curry said. "If you have information, if you have the tools that you need to to plan and prepare, then we can do a lot to keep California safe."
