IGBBT: Too Much of a Good Thing

So... 7 months ago, I had recently learned of an highly interesting and unusual event where a tropical cyclone almost formed over Lake Huron in September 1996. I realized that the more extreme global warming in one of my alternate histories (Into the Wild Black Yonder) could provide the final push to allow that to happen, and so I detailed that in Into the Wild Black Yonder: A Butterfly Effect. I especially found it interesting not only as it was a disaster made worse conditions in IWKY, which I mostly find a more blessed_timeline than Boring Old Real Earth (partially as political events [which could lead to man-made disasters] are incomplete), but because it could very easily occur in the future with given our current trajectory.

Now, as can be inferred from its name, It's a Great Big Beautiful Tomorrow is more blessed than either BORE or IWKY (because it's my 100% serious communist Wank). It has had very little political chaos since the 1920s, and global warming was solved in the 1960s. So, surely a disaster couldn't be made worse by situations there, especially in the same manner, right? Right? 

(Note: Unlike the "prequel" of this, the description here will be LONG. Like, Enoch Phase-2 and expanded XF-115 long. 'Cause there's a lot of lore behind this. Enjoy. )

Part I: Background:
After the American theatre of the World Revolution concluded in 1922, the habitation of the American Southwest occurred in a markedly different way than in BORE. Due to the restructuring of the agricultural system to a more locavorous one, no desire for a cheaper labor force, and the influence of Native tribes, settlement was generally lower in volume, with population figures generally lagging by ~25 years in comparison to BORE.

By the early 1950s (especially due to the lesser presence of irrigation in the basin to provide water through runoff), it was realized that the Salton Sea—starting to develop a tourist industry as IRL—was beginning to die. Without an outflow, it would become increasingly saline and hypertrophic and eventually dry out completely, opening its sediments to the open air where they could get blown away in large dust storms. So, as part of Project Ploughshare, a plan was drafted to carve a new canal from the Colorado River to the Salton Sink, and then from there to the Laguna Salada and back, reconnecting with the original Colorado Delta, partially using nuclear explosives. Consensus democratic caucuses of the residents of the affected area were held on the proposal, which resulted in it being accepted under the grounds that assistance be gathered to reconstruct their settlements.

In 1955, ground was broken. At least 25 settlements were evacuated (22 totally, 3 partially [Calexico, El Centro, and Indio]), disassembled, and reconstructed at the future lakeshore using local, volunteer, and lottery labor. On 1957–03–21, excavation and construction had ceased, and the entire flow of the Colorado was diverted into the Salton for the first time since 1906. On 1959–10–31, the New Branch of the Colorado River spilled over into the ocean, and the Salton Sea and Laguna Salada were renamed by the American Geographical Society to Lake Cahuilla and Lago Coyote, respectively, the former alluding to the similar prehistoric lake (although the engineered one includes safeguards to ensure it will not have a similar chaotic cycle).

After the filling, the population of the Imperial and Coachella Valleys exploded to BORE levels, with the massive lakes preferred over the Pacific coast for aquatic recreation (sans surfing) due to their warm, fresh water, weak tides and waves, and on the northern and southern coasts of Cahuilla, the same horizon. Many resort towns like Mumbai Beach, Desert Beach, Aruba Shores, Cahuilla City, Cahuilla Sea Beach, North Shore, and Villa Coyote sprung up, far more prosperous than their equivalents in BORE. The influence of the lakes moderated and moistened the climate of their surroundings, the latter effect being especially strong by the mountains—while initially evaporation reduced the delta flow of the Colorado by 50%, the increase in cloud cover, decrease in temperatures, and induced precipitation in the Salton Sink and Colorado watersheds reduced the effect considerably. This resulted in more settlement, reduced the need for irrigation in the valley's orchards and farms, and even allowed rain-fed agriculture in some areas. An additional benefit for habitation compared with the tropical Atlantic and Pacific was the absence of hurricanes... oh. oh no...

Part II: Cyclone:
In 19-76–09–07, Hurricane Kathleen came into being in an almost identical fashion as in BORE. Early on 1976–09–09, the Weather Modification Pilots Association decided not to use mass cloud-seeding in order to weaken the storm due to its low projected intensity and drought conditions in its affected area, projecting low damage. They were roundly criticized for this decision after it hit.

At 11:30 UTC-8 on 1976–09–10, now Tropical Storm Kathleen crossed the Sierra Juarez mountain range, causing it briefly to weaken into a Tropical Depression in addition to slowing its forward motion from 35–38 mph to 16–17 mph. Almost immediately after crossing the range, it felt the 86 °F (30 °C) waters of the lakes and a humid, still air layer. The cyclone began rapidly intensifying again, reaching sustained winds of 55 mph (with gusts up to 75 mph) from 35 mph by 16:30 UTC-8 on 1976–09–10. The storm even developed an eye, not present in its hurricane manifestation.

Storm surge resulted in the New Branch of the Colorado River stagnating, even reversing from 16:00 to 19:00, causing minor saltwater intrusion in Lago Coyote. The chaotic surface of that lake took the life of the storm's first victim by drowning. Incredible rainfall resulted in what would have been considered a 1-in-4000-year flood prior to the project in Ocotillo and several other areas—even though Ocotillo had far more solid foundations than in BORE, devastation was the same, with 6 people perishing. Streets eroded 3 feet below their initial level. Lake Cahuilla rose 6–8 inches just due to rainfall and drainage, with a storm surge of 0.5+ m on the north coast and 1+ m on the south coast of Cahuilla further inudating it, which was especially extreme in the south due to its flat topography. The absence of seawalls and open shores of the lake encouraged large-scale flooding, leading to 30 deaths on the lake and in communities in the Salton Sink, almost all due to drowning.

Twice the entire former annual precipitation was dumped on the Coachella Valley, with the Whitewater River overflowing its banks. 22.03 in (556 mm) of rain fell on San Gorgonio Mountain over the course of several hours, along with 14.76 in (375 mm) on the formerly-desert Orocopia Mountains, causing massive erosion outside the olive orchards and planted stands of New Mexican piñon-California juniper woodland. At 20:30 UTC-8, the system again weakened from a Tropical Storm to a Tropical Depression as it began passing the Little San Bernardino Mountains.

Now within the Great Basin, Tropical Depression Kathleen continued producing heavy rain, with several inches falling over Lancaster. Some rain even passed into the Central Valley, with Bakersfield recording 1 in (25.4 mm), and Death Valley a whopping 2 in (50.8 mm), temporarily recreating Lake Badwater. Flash flooding was recorded in Las Vegas, resulting in the death of a family. For an hour after 22:00, gusts of Tropical Storm force were recorded in Hurricane, Utah. In the morning of 1976–09–11, Kathleen finally became extratropical over Central Nevada. A Fujiwara-like interaction with a Pacific extratropical cyclone pulled over land prolonged its life, causing moderate rainfall over Utah, Idaho, and Oregon late on 1976–09–11 and early on 1976–09–12. One man in Idaho drowned trying to cross a swollen stream. After losing a defined center at 03:00 UTC-8, the system finally died late on 1976–09–12, causing light showers over Osoyoos, British Columbia.

Part III: Lesson:
In the aftermath of the cyclone, a program was put into place to ensure that such destruction and loss of life never happened again. For example, 2-meter levees were constructed around populated areas by Cahuilla, the vegetation projects for the surrounding mountains were quickly finished, power lines were buried, and gravel roads were paved over with plastic binders to reduce washout hazard. Weather modification crews were alerted to the devastation potential to the area, though it had to be recognized that tropical cyclones are an important element in Earth's climate and that several other areas are far more at risk, leading to higher modification priorities there. As a result of this program and the advance of medical technology, when Hurricane Nora followed a similar track and produced similar effects 21 years later (though with "only" ~60% the precipitation near Cahuilla and Coyote due to the slight track differences), zero were killed in the former Southwestern United States, unlike even in BORE. So, I guess the real-world lesson is this: All engineering projects can have unintended consequences—sometimes lethal—and adequate consideration of those aspects can mitigate them.

Note: Although in the right place, I really wish that I could find a good image of a lower-Dvorak-number cyclone—this one males Kathleen look far more intense than it actually was. 

As always, if you have any thoughts or questions, please say 'em.