A Tale of Two California Floods
In early 2024 two dramatic atmospheric river events dumped rain on Southern California. El Ni?o heated sea surface temperatures in the Pacific Ocean from mid-2023 through the winter of 2024, more than doubling the major precipitation events to reach the US Pacific Coast in that period.? Despite similar forecasts and rainfall amounts, the effects of these events on their respective cities was vastly different. The first event resulted in devastating floods for San Diego on January 22nd, 2024 while the second atmospheric river took aim at Los Angeles only two weeks later on February 6th, creating almost no flooding.?
These events took place while I was working at ICEYE, a satellite company specialized in monitoring natural disasters like flooding and wildfire from space. This gave me a front row seat to the machinery of weather forecasting, observed impacts from satellite imagery, media monitoring, and customer feedback from insurance and emergency management. I was baffled by the wildly different flood outcomes in California. If anything, I was expecting a worse outcome in Los Angeles, but the opposite happened. The atmospheric river in Los Angeles left me scratching my head. Why were flood forecasts so wrong? Where did all of that water go? To make sense of the situation, I returned to my roots in municipal infrastructure and investigated the historical context of disaster preparedness in the region. A Los Angeles flood in 1938 is the key to this story, and it still affects flood outcomes today.?
Zoomed Out Perspective
From a global weather perspective, the two atmospheric rivers of 2024 were about as close to a controlled experiment as it gets. In a broad sense, San Diego and LA are quite similar. They are neighboring cities, situated similarly on the coast with comparable climates, terrain, city age, and sprawling car-centric patterns of development. As a region, this area of California is characteristically dry, known for its droughts and wildfires. Big rain events are not common except in strong El Ni?o periods, with local dry spells ranging from two to twenty years in between.
The period of recurrence between floods is just long enough to erode collective memory of their existence. There's every reason to believe that the last time either of these cities saw a major flood event was well before the transplants moved in and the younger generation came of age. Elected officials run in short election cycles, most likely on agendas of wildfire, drought, and tax cuts. The last flood might have happened before your mortgage loan officer or insurance agent started their careers. Even if the gray-haired person in the corner office remembers, the institutional perceptions of this risk has been downgraded over time on financial transactions and investments.
San Diego - January 22, 2024
On January 22nd, an atmospheric river brought ~3 inches of rain to San Diego, California in just a few hours. This was enough to displace 1,200 people and damage about 600 homes. Aside from weather forecasters, most people (especially on the East Coast US) were sleeping on the news of rain headed for San Diego. Customer communications didn't heat up for my job at ICEYE until the flooding approached disaster levels. The media reacted with shock and horror as pictures circulated of flooded homes, landslides, and devastated citizens. People sobbed on camera for emergency relief and funds.?
In the aftermath of the flood, officials in San Diego fielded uncomfortable questions about the inadequacy of its flood control systems. Stories broke about how badly underfunded the San Diego sewer system was, and how attempts to invest in infrastructure had been postponed for decades. The sewer upgrades needed to prevent another similar disaster were estimated to cost $1.6 billion.
Los Angeles Atmospheric River - Feb 5 - 6, 2024
If you had turned on the news Monday morning Feb 5th, the situation in LA looked bad. CNN was already reporting 100 landslides, rising rivers, and more rain in the forecast.
Flood companies released their predictions showing heavy flooding in urban Los Angeles. CNN was reporting on a scary-looking flood estimates by FloodBase on the morning of Feb 5th, and ICEYE's internal meteorology predictions looked similar. This was a few hours before ICEYE released its first satellite-based flood observation, so we didn't know what the final flood would look like yet. Our customers were nervous, and I was too after what happened in San Diego. I braced for impact at my job as we waited to see how bad the damages would be.
Surprisingly, Los Angeles experienced almost no flooding from the February atmospheric river. The outcome certainly did not match the Floodbase predictions printed in CNN. For ICEYE's insurance clients, there were almost no flood claims. Emergency management was busy in the hilly regions of Los Angeles because of landslides, but not because of flood. It's important to note that landslides are not covered in flood insurance products even when caused by water. Landslides might be covered with earthquake insurance, but this is a gray area as water-caused landslides might be excluded. If you look carefully at the earlier CNN photo, it's mud and debris from a landslide, not flood, that the man in the raincoat is cleaning.
Los Angeles Flood of 1938 - History Shaping Future Disasters
The flood of 1938 is credited with spurring the flood control system in Los Angeles. It was not the biggest or the most deadly flood, that title goes to another atmospheric river in 1862. Two more major flood events piled on Los Angeles in 1914 and 1934, and then just four years later in 1938. By 1938, Los Angeles development was booming in precarious floodplain areas, concentrating exposure in harm's way. The damage from the flood of 1938 was estimated around $1.69 billion in 2023 dollars, impacting over 7,000 properties and killing more than 100 people.?
The 1938 flood prompted a plan to channelize the Los Angeles River. Part of the reason the flood of 1938 got so much attention was because its impact on movie studios. Universal, 20th Century Fox, and Warner Bros were all impacted by the 1938 flood. The movie studios had become major economic players in Los Angeles, and halted production was a blow to the region. Hollywood pushed back and became vocal advocates for infrastructure investments to prevent future floods.
In its final design, the Los Angeles River was channeled into concrete walls, accompanied by a series of dams and storage areas designed to handle flashy events and atmospheric rivers. Today, this channelization is synonymous with the LA Landscape. It has featured in over 50 movies, TV, and videogames. Hollywood advocated for the creation of the channels and has used them in backdrops for films and entertainment ever since. In the dry periods, the robust channels look bizarre with only a trickle of water running through barren concrete canyons. Memory is all but lost about why the channels exist.
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Conclusion
The Los Angeles flood control system handled its atmospheric river by design, preventing losses from flood in February of 2024. By comparison, the January flooding in San Diego revealed underinvestment in municipal infrastructure, making it vulnerable to preventable flooding. Municipal infrastructure plays an outsized role in natural catastrophe outcomes, yet it is underutilized in insurance modeling.?
With so much rich history, why do private insurance models fail to include municipal infrastructure in their predictions? It's not enough to look at claims history because these events are rare with wide gaps in insurance coverage, so there's little data to pull or simulate. I find it bizarre when insurance operates as though each property is an island, divorced from its context and place. Risk needs to be accessed at the community level, incorporating investments in infrastructure and disaster preparedness. Especially as risk portfolios are aggregated, geographic hotspots of poor planning really hurt the bottom line.?
To plan for a climate future, we must look back at successes and failures to assess vulnerability. Planning for what has already happened is the first step in handling the impacts ahead. The Los Angeles system was designed to withstand the flood of 1938, but it would likely break with a recurrence of the 1862 flood. How has exposure reconcentrated in the system's vulnerable places, and have infrastructure investments kept pace? Do insurance models account for these spatial variabilities? Coasting on 100 year old infrastructure and forgetting about reoccurring hazards is not good practice for resiliency panning or financial risk management. Without intervention, the only thing we can count on is a reoccurrence of the 2024 San Diego disaster, or worse.
References
El Nino 2023-2024 Season Explained: https://www.foxweather.com/extreme-weather/west-coast-51-atmospheric-rivers-2023-2024
People displaced in San Diego: https://www.nbcsandiego.com/news/local/more-than-1200-plus-san-diegans-still-homeless-after-the-great-flood-of-2024/3429816/
San Diego Press Conference: https://www.youtube.com/watch?v=I8XBdf5Wlf0
San Diego Infrastructure Funding Gaps: https://www.sandiegouniontribune.com/news/politics/story/2024-02-05/not-just-stormwater-san-diego-needs-more-than-6-billion-for-crucial-infrastructure-but-has-just-a-quarter-of-that
Photo - San Diego Flooding: https://media.npr.org/assets/img/2024/02/05/gettyimages-1986533842-76d38b769487ed012ea93752e4898bda899a6e76-s1200-c85.webp
January Atmospheric River Graphic: https://disc.gsfc.nasa.gov/media/image/988bfa7777d64e6d91041245633e42e5/sandiego_animation.gif
CNN - Los Angeles 100 mudslides reporting: https://www.cnn.com/2024/02/04/us/pineapple-express-storm-california-weather-monday/index.html
CNN - Los Angeles flood prediction map using FloodBase: https://www.cnn.com/2024/02/05/us/map-california-weather-forecasts-storm-dg/index.html
Background for LA floods: https://www.pbssocal.org/shows/lost-la/the-southern-california-deluge-of-1938
Loss estimates for 1938 flood (paywall blocks original source): https://en.wikipedia.org/wiki/Los_Angeles_flood_of_1938
Photo - LA River Channelization: https://en.wikipedia.org/wiki/Los_Angeles_River#/media/File:Los_Angeles_River_Bridge_B&W.jpg
Pop culture references to the channeled LA River: https://en.wikipedia.org/wiki/Los_Angeles_River
Hollywood impacts from 1938 flood: https://www.hollywoodreporter.com/news/local-news/los-angeles-flood-1938-1235302200/
ARkStorm explained: https://weatherwest.com/archives/16626
LA vulnerability to future large storms: https://www.latimes.com/california/0000018d-ccbf-dc86-ad8d-cfffd7240000-123