The classic US film Chinatown starts in the 1920s in LA, at a government inquiry into the building of a dam — and the lethal disaster of a previous, excessively tall, dam collapse, all of which is really a cover-up for corrupt property deals. Los Angeles was built on water stolen from surrounding counties, destroying them economically and ecologically.

It’s an impossible city, a very obvious metaphor for the US in the film, and this week it turned from allegory to prophecy when nearly 200,000 people had to be evacuated from the area near Oroville, about 150kms north-east of San Francisco, after a concrete spillway that takes the run-off looked to be on the point of collapse. Oroville is the US’ tallest dam. The spillway was collapsing because the ground had caved in beneath it, at which point not only the Parks and Wildlife Service, but also the helicopter-borne Anti-Allegories-of-American-Hubris Squad were mobilised. US authorities have attributed the cave-in to “inexplicable” geological events, but, well, Swiss dams don’t suddenly collapse,* while Nigerian ones, for example, do.

The event is another ely** in the great American infrastructure story. The Oroville dam is 50 years old; much US infrastructure is at least 40 years old, because that’s when the significant investment in it started to, erm, dry up. No one seemed to have been concerned about the viability of the spillway for years; suddenly they were, when torrential rains overfilled the dam, which is a little late. The event is significant not only because it’s another US piece of infrastructure that is simply and literally crumbling or rusting away, but because it concerns water.

[Rundle: the world is upside down, and traditional parties don’t know how to right it]

This time it’s too much of the fresh stuff, threatening to flood prosperous towns. Last year, it was too little of it, in Flint, Michigan, the city that became a cause celebre after it became clear that the entire water system was contaminated, due to non-elected officials switching the supply source from the main Detroit supply to the Flint River, which had been an industrial run-off for the decades when GM and other car companies had dozens of plants in the area.

The auto industry is gone from Flint, so the city has gone broke, so the council was replaced by administrators, so they saved money by switching the water supply. The city was mainly white in its industrial heyday; it is now mainly black, and the water supply switch, and subsequent failure to report the contamination or act on it, was plainly racist in its actions. Around that, a huge campaign developed, often emphasising the race politics angle, and culminating with the visit of Hillary Clinton during the 2016 primaries, to slate Bernie Sanders on his lack of black community support. Clinton hasn’t been back, and Flint’s water is still contaminated.

The Oroville spillway collapse, as well as being a great potential country-and-western song, complements Flint in one big message: American infrastructure is coming down, and it will soon come right to the centre of US politics, and be the point around which its re-orientation continues. Barack Obama proposed a multibillion-dollar program to rebuild infrastructure using green technologies, and creating new industries and apprenticeships, in his first term. Right-wing Democrats in Congress would only give him part of it, and the post-2010 Republican House wouldn’t give him any of it. When he proposed an infrastructure bank in his second term, it was simply blocked.

Now it may be unblocked, as the Trump/Bannon White House tries to shift the right’s economics from free market to nationalist Keynsianism, and bully Congress into coming along for the ride. For the right, and everyone, the politics are messy and complex. Business Republicans will be against it on fiscal grounds; so will Tea Parties, many of whom will have supported Trump on cultural politics. The Democrats will either have to vote it through or be seen to be blocking American jobs. Barack Obama never used the presidency as a bully pulpit, his greatest political failing; he should have been out there, daily, berating the “do-nothing” Congress. You can be sure that Trump will be, if Congress is resistant.

However, the added complexity is that the Trump/Bannon administration won’t be doing this as some form of mixed public/private partnership: they intend to basically fork over huge government sums to private contractors in a vast payday for Big Concrete, Big Construction, Big Engineering and Architecture — y’know, all the folks who build big hotels around the world. That sort of kickback won’t matter to the voters if the money actually flows to ground level and stuff gets built, and private companies may indeed allocate it more efficiently. But they might also sop most of it up in fees and consultations, etc, because really, who wants to actually build stuff these days? Some of it would then fall to the ground in some paltry, half-built projects. Trickle-down economics, rather than the spillway required.

[Rundle: is Donald Trump staging an actual coup?]

Should that be the case, then, were the Democrats and the left capable of exploiting it, not only would Donald Trump be in trouble, but so, too, would the whole right nationalist political project, and rather quickly. The Democrats should obviously enthusiastically support a Trump/Bannon infrastructure fund proposal if it eventuates, claim co-credit for it, if it starts to succeed, and slate the White House for its failure, if nothing happens, and win back the White House in 2020. Much of the social and cultural damage Trump is doing and will do, could then be repealed and repaired, in parallel with the renewed economic program, about which, at which point, many opponents of progressive policies wouldn’t give a, well, a well, um, it just wouldn’t matter to them that much.

*the 1965 Mattmark disaster occurred when a glacier collapsed onto a dam construction site, the rule-proving exception.

**an “ely”, according to The Meaning of Liff, is the “first small inkling that something somewhere has gone terribly wrong”. It’s the one word from that collection that has a chance of making it into common usage.