...when do we start talking about abandoning the Gulf Coast? Right now there's nowhere for millions of people to relocate to.
It's time to start building Cities Of The Future. We've never done that, build a new city from scratch. The Chinese have been doing it, as I understand it a a failure of their economy to properly allocate resources. We never have.
You can't find a spot where there won't be torrential rains. Here in Colorado we had a major flood a few years back. But you can find spots with enough drainage.
Put the lowest part of the infrastructure 250 feet above current sea level. Harden the city against megastorms by putting it mostly underground. Keep the nearby area clear to prevent wildfire (soon that won't be a problem, nothing of note will live on the surface).
No private vehicles, no exceptions, and no need for them.
Power it entirely with renewables. Run fresh water lines in from the coast, from offshore wind-powered desalination plants. Multiple lines for redundancy.
Grow food in underground greenhouses. Import/export as little as possible. Connect cities with high speed electric rails powered by renewables.
No slums. No luxury apartments.
Start to dismantle the heavy industry by the coast. Eliminate the oil and gas infrastructure, we won't be using it any more. Move chemical plants to less vulnerable spots, connect them to workers with rail lines. Defuel the nuke plants and start the decommissioning process. I have no hope that it can be completed in time.
Where will the money come from? To start with, use the money that would otherwise have been wasted rebuilding doomed settlements. Then implement a wealth tax, together with a 100% inheritance tax (with a generous exclusion). It will take all the money there is, and that won't be enough, but we need to do what we can, and we need to do it now.

@Pluto's Republic
@snoopydawg

I no longer think there is any meaningful steps individuals, regardless of wealth, can take to survive. My reference for this was the drought in Sao Paulo. At the other end of the water spectrum we see Houston.
That isn't to say that we can't take steps to reduce our individual footprints, help others, prepare for short term emergencies, or try to keep our heads above economic waters. We can, and we should.
But classic survivalism (I guess survivalists call themselves "preppers" these days) just won't cut it. It was predicated on the idea (fantasy?) of societal collapse in the context of a world that still supports human life. That's not the world we're heading for.
Food, water, shelter.
Your shelter can be wiped out by winds, flood, or wildfire. Those factors can't be addressed individually, only by a functioning society. You can try to manage risk when selecting a site and building your shelter, but megastorms and megafires can easily overwhelm you. You flee and try to pick up the pieces later.
Your carefully designed, lovingly tended Amish farm quits producing food when the rain stops and the Death Valley heatwaves come. No food, no water, at best you're just another refugee.
Your best bet for water supply is to be connected to an urban water system, hopefully one with surplus supply and ample storage to carry you over the drought years. The first thing you can expect during drought is water restrictions. What can you do then?
I told one friend who was looking for things to perhaps do was to set up net-metered solar on the roof, battery backup, and a hydroponic gardening setup in the basement, probably with a cistern plumbed in. With luck you could leverage a meager water supply to produce some fresh veggies to supplement stored food. That would last for a while, until the municipal water system failed altogether. Might buy you a year or two.
I'm convinced that the uber rich think they can retreat to a bunker somewhere. Perhaps the most elaborate scheme I've seen is Larry Ellison's Lenai project. That might last for a decade or more, but it's still on too small a scale to endure.
We're out of time to fix this. We need to buy more time to geo-engineer the planet back to a climate we can thrive in. That's going to take centuries if not millennia. We need scientists, engineers, technicians, medical people, educators, and everyone else it takes to maintain and extend technological civilization over a hundred generations.
Even a luxury bunker housing a rich psychopath and his hangers-on won't make it. Even a military installation set up to survive nuclear war won't last long enough. We don't know how to build things that function for thousands of years. None of them will house enough people. I don't know how many people it takes to maintain civilization, but millions certainly, maybe hundreds of millions.
Individuals won't make it. We either survive together or go down together.