Does this mean California is more likely to get mega flooding?
Other states seem a lot worse off. Water table is closer to where people live, there's a lack of topology to actually run water out in a lot of cases, there's been little investment in managing water for stormwater for property damage abatement or power or irrigation like in CA where the topology really incentivized massive investment in all of that over the last century.
Next year a super bloom then the following year massive wild fires.
rain -> fuel -> fire
The steering of the jet stream seems to have some qualitative changes in these conditions but also more chaos. It could steer storms anywhere along the coast, so different parts of CA, OR, and WA get different impact. Just in my lifetime in CA, I've witnessed some very wet El Niño winters but also some drier than average.
The biggest precipitation threat on the west coast seems to be a repeat of some of the biggest flooding events known historically or geologically. But, these are relatively infrequent and most of the record predates any understanding or tracking of the El Niño oscillation. So the correlation cannot be stated so clearly. These are atmospheric river events which seem to stall, producing heavy rains over the same area for a much longer period.
Just in the recent centuries of CA history, there have been massive floods in northern and southern regions in different month-long rain events. There have been improvements to flood control infrastructure since then. But, the only reason those events aren't known as the most costly is because there wasn't as much economic development here back when the floods happened.
Our usual storms sweep through an area the heaviest rains over just part of a day. Our varied terrain means that each individual storm also has very uneven rainfall amounts due to orographic intensification. Prominences with the right aspect towards the wind will get far more accumulation. Our watersheds can absorb quite a bit of this, but even those brief rains can cause localized flooding.
If the rain continues for many days in a row, we will see widespread mudslides and flooding of larger rivers, basins, etc. Some of the historically extreme events had rain persisting for over a month!
Edit: along with these "mega storm" scenarios, we also have evidence of "mega droughts". It's worrisome to imagine what challenges may come from a more energetic and chaotic climate.
El Niño is the “warm phase” of the El Niño-Southern Oscillation and features warmer than average ocean surface temperatures off the coast of Ecuador and Peru in the equatorial eastern Pacific Ocean.... Historically, the presence of El Niño conditions tilts the odds in favor of wetter than normal precipitation across the southern third of the state. The relationship between El Niño and cool season precipitation is weaker in the central and northern parts of the state.
Flooding is possible, particularly if dams exceed capacity, perhaps exacerbated by earlier snowmelt and peak runoff. Landslides are a more widespread, and less manageable problem, particularly as loose-material slopes are waterlogged. The deluge -> high growth -> heavy fuel load -> large wildfire -> landslide cycle is one that's become fairly well-known in California.
Levee failures within the Sacramento Delta or Central Valley could result in very large-scale flooding, affecting agriculture or communities.
The San Francisco Bay Area may see "king tides" and general flooding throughout the bay and delta region, particularly during December and January, and all the more so if high tides coincide with heavy river run-off. Remember that the entire Central Valley of California, nearly 500 miles long north-to-south, drains out through the Bay. Prevailing winds may create a wind setup or seiche which can result in flooding along a some but not all shorelines, or alternating across a body of water.
Aquifer fill rates are slow, and are generally predicated on large-scale flooding. Prior to modern flood control (dams, river channelisation, levee construction), in which much, and occasionally effectively all of California's Central Valley (as well as large riparian valley systems in Oregon and Washington) would flood.
See the Great Flood of 1862: <https://en.wikipedia.org/wiki/Great_Flood_of_1862>.
Reservoirs provide parlous slim protection against landslides of elevated slopes. Those are affected by upslope water saturation (the stuff that's on its way to fill your aquifers in coming months or years), not floodplain innundation. It's exacerbated by fire-cleared hillsides, particularly those which burn ferociously hot, killing plant roots and baking soil. Those fires are not historically typical, but have been the conditions experienced with greatly increased frequency since the 1990s.
Cattle don't graze chaparral, oak woodlands, or ponderosa or Douglas fir forests. Those have been what's been burning.
Your suggestions / assessments are at a far remove from reality.
We also have one of the more advanced waterwork system in the US to support Central Valley agriculture, so a lot of the worst aspects can be somewhat managed.
It's bad that such dramatic climate change is happening, but we're definetly lucky to live in the West Coast because we won't face the brunt of some of the worst aspects of the El Niño comparatively and have the infrastructure to deal with it.
Sadly, the brunt of climate change will be felt by the poorer half of the world.
The Lima Prieta Quake and the 1990s floods led to a lot of future proofing in Californian infra. The last major thing left is transmission weathering, which PGE and Sac are fighting over.
Also, most of our infra is state funded which gives us a lot of leeway.
Like I said before, it's bad that we're in this position and it's only going to get worse, but we're in one of the better places that can survive these kinds of shifts.