Cascading multiple climate disasters are occurring all over Earth. In today's headlines, California is experiencing raging muddy water from hillsides and heavy rainfall from uncountable drops of moisture from mighty atmospheric rivers repeatedly slamming into the Golden State.
Like hurricanes, the atmospheric rivers provide needed water critical for the region's hydrology cycle. In The Washington Post ( no firewall), Kasha Patel notes that the "massive rivers, which sometimes carry 15 times the water volume of the Mississippi River, deliver half of the western United States' total precipitation in less than 15 days."
When rain falls all at once over land in a mega-drought, the soil acts as concrete; the water spreads everywhere as the ground can't absorb the runoff. The consequences of a mega-flood can destroy energy and other infrastructure and cause deaths from drowning.
Meteor Blades reports on why such disasters are becoming more frequent, intense, and dangerous. Please read the hard work and critical findings to understand why we are at a turning point. U.S. greenhouse emissions, which need to be plunging as we head to 2030, rose again in 2022
As many readers know, global heating of the oceans is increasing the amount of moisture the atmosphere can hold. As temperature rises, evaporation increases, and this phenomenon threatens even more devastation as time passes.
For the residents of Southern California, these rivers "steered by the low-level jet stream, the rivers are migrating toward the equator making the LA megalopolis the future target of the extreme danger they pose.
Patel writes about the snowpack peril that piles up in the mountains only to be reduced rapidly during the unrelenting storms with rain and the months ahead by heat waves.
Atmospheric rivers play a critical role in supplying mountain snowpack, which serves as an important source of freshwater as it melts in the spring and summer. Some research shows the weather systems provide about a quarter of the snowpack in the Sierra Nevada. Yet as temperatures rise, snowfall is decreasing.
Snow may vanish for years at a time in Mountain West with climate warming
Studies have already shown atmospheric rivers are delivering less snow in the northern Sierra Nevada, instead falling as rain because of Earth’s excess warmth. Some of the rain can run off into rivers and cause flooding. In some cases, the rain can also land on top of snow, accelerating melt. In February 2017, rain from atmospheric rivers fell atop snow, which helped push the main and emergency spillways of the Oroville Dam to their brink.
“The real risk here is California’s whole infrastructure was built with what we understood of the snowpack, meaning a natural reservoir through the whole winter,” said Anna Wilson, who studies atmospheric rivers at Scripps Institution of Oceanography. “Now we’re getting into situations where we’re getting more rain throughout the year. Sometimes they have rain on top of snow.”
Researchers project such rain events will multiply across the western United States. Rain-on-snow events are expected to increase at higher elevations, raising the flood risk most notably in the Sierra Nevada, Colorado River headwaters and the Canadian Rocky Mountains.
The risk of multiple compounded disasters from climate change is jaw-dropping. I wrote on the topic recently, where 90% of the world's population will face compound disasters in the years and decades. Rainfall increases vegetation growth, heat and drought turn the vegetation into fuel, and wildfires erupt, many sparked by an increase in lightning strikes, also implicated to changes in the climate. Finally, the heavy rains fall on burn scars, and landslides and mudflows barrel over the land below the burned areas above.
Amir AghaKouchak, Professor of Civil & Environmental Engineering and Earth System Science at the University of California, Irvine, writes in The Conversation. The Conversation is creative commons, and articles can be republished with attribution to the author.
You are free to republish the text of this article both online and in print. We ask that you follow some simple guidelines. Please note that images are not included in this blanket licence as in most cases we are not the copyright owner. Please do not edit the piece, ensure that you attribute the author, their institute, and mention that the article was originally published on The Conversation.Rivers of muddy water from heavy rainfall raced through city streets as thousands of people evacuated homes downhill from California's wildfire burn scars amid atmospheric river storms drenching the state in early January 2023.
The evacuations at one point included all of Montecito, home to around 8,000 people—and the site of the state's deadliest mudslide on record exactly five years earlier.
Wildfire burn scars are particularly risky because wildfires strip away vegetation and make the soil hydrophobic—meaning it is less able to absorb water. A downpour on these vulnerable landscapes can quickly erode the ground, and fast-moving water can carry the debris, rocks and mud with it.
Officials warned of a risk of debris flows near several recently burned areas, including near Santa Barbara and Los Angeles, Monterey and Santa Cruz counties and the Shasta Trinity National Forest.
Five years ago, on Jan. 9, 2018, a deadly cascading disaster struck Montecito, a community in the coastal hills near Santa Barbara.
The cascade of events had started many months earlier with a drought, followed by a wet winter that fueled dense growth of vegetation and shrubs. An unusually warm and dry spring and summer followed, and it dried out the vegetation, turning it into fuel ready to burn. That fall, extreme Santa Ana and Diablo winds created the perfect conditions for wildfires.
The Thomas Fire began near Santa Barbara in December 2017 and burned over 280,000 acres. Then, on Jan. 9, 2018, extreme rainfall hit the region—including the burn scar left by the fire. Water raced through the burned landscape above Montecito, eroding the ground and creating the deadliest mudslide-debris flow event in California's history. More than 400 homes were destroyed in about two hours, and 23 people died.
These kinds of cascading events aren't unique to California. Australia's Millennium Drought (1997-2009) also ended with devastating floods that inundated urban areas and breached levees. A study linked some of the levee and dike failures to earlier drought conditions, such as cracks forming because of exposure to heat and dryness.
When multiple hazards such as droughts, heat waves, wildfires and extreme rainfall interact, human disasters often result.
It's also important to recognize that human activities and local infrastructure can affect extreme events. Urbanization and deforestation, for example, can intensify flooding and worsen mud or debris flow events and their impacts. That was evident in the videos of muddy water pouring through streets in Santa Barbara County on Jan. 9, 2023.
In a recent study, colleagues and I also looked at the risks to energy infrastructure from cascading disasters involving intense rain over burn areas, focusing on natural gas pipelines and other infrastructure. Our results showed that not only will natural gas infrastructure be increasingly exposed to individual hazards, creating the potential for fires, the chances of cascading hazards are expected to increase substantially in a warming climate.
With compound and cascading events likely to become more common in a warming world, the ability to prepare for and manage multiple hazards will be increasingly essential.
Gulp. Please take care, California; you are in my thoughts.