Most of the most flood prone areas in CA have been significantly neutered over the decades thanks to massive water projects. There was a time when the LA river would destroy LA routinely. Now everything is channelized. At risk communities are probably the handful of remote ones that do not have great infrastructure, but I'm not even sure where those might be given how the state seems to be able to build thousands of debris flow cement storm drain setups in relevant areas.

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.