Right, for Miami, you might want kwelschermen (or a variant thereof: deep impermeable cutoff walls, doesn't need to be concrete, can be made by clay injection too) , californian style water injection, locks that reject salt water. Different place, different geology, different tools. No place is exactly the same.
Thing is I figure you need some form of water board to manage it. A political entity that's all about "here we are and here we stay". Once they're set up they're pretty reliable (there's one that's still paying interest on a 370-year old bond https://www.youtube.com/watch?v=cfSIC8jwbQs )
Put dikes around it, make channels to collect the seepage, pump water out of channels over the dikes into the sea. Problem solved in the same way the Netherlands has been solving this problem for many centuries.
The pumps can run on solar power with some diesel backups for when the sun doesn't co-operate. As long as the system is kept in good shape and the channels are kept open Miami can lie several meters under sea level without the need for further action. The house I lived in in the Netherlands was at -4.5 m below sea level, it is still standing and will remain doing so if history can be a guide.
I imagine this type of system is not designed for large, sudden and prolonged inundation of water, something New Orleans faces from seasonal hurricanes and their storm surges. Or maybe it is and it’s just a question of magnitude?
Yes, it is a question of magnitude and also of planning for those specific threats. To catch storm surges you'd use catch areas, dry basins and some sacrificial areas - parks come to mind - where storm surge water can be temporarily held until the pumps catch up. There should be extra pump capacity held in spare for these occurrences, both regular pumps as well as mobile units which can be placed where the need is highest. You also don't just use one dike around the whole area but divide it into sections with 'sleeper dikes' - dikes which normally do not border flooded areas but which can catch water which somehow makes it past the main dikes - behind the main ones. There are reams of literature on the subject to be had from places like the Netherlands where all this has been daily life for centuries, it is not a new problem.
The problem is saltwater intrusion into the drinking water table - a problem New Orleans only has one when it comes up the Mississippi river - Miami is a whole different level
That can be solved using desalination of seawater, an energy-intensive process which is tailor-made for the abundance of solar power in the area. If for some reason desalination is not deemed sufficient it may be possible to slow the seepage by creating deep barriers between coast and land [1]. If this results in groundwater emergence so much the better, just pump it out and send it to the water treatment plant. Excess water can be pumped elsewhere, either over the dikes or into the ground outside the dikes or wherever else it may be needed or beneficial. Since pumps are needed anyway the criticism in the article - reliance on pumps is costly and can lead to a point of failure in flood mitigation plans - is negated. Also, pumps have been used as part of flood mitigation plans for centuries in places like the Netherlands so there is a lot of data to be found for those who need it.
Uhh... "those in the know" are the actuaries and if you were to take away the subsidies provided for homeowners and developers to deny basic mathematical facts, the entire area would be totally unbuildable already.
i work in insure tech, in the E&S space, which is where all of the flood and wind polices gets placed. Actuaries have nothing to do with it --- the cost of hurricane insurance comes from Moody's RMS and Verisk AIR, the only two CAT models the carriers and re-insurance companies use. Actuaries price the non-cat risk.
This is mostly a pedantic point that it's not actuaries doing the pricing, but a different set of risk analysts using a different suite of tools, right?
[Edit] The following comment can be read very snarkily but that is not the intention. I'm legitimately interested + curious:
Very interesting! Does it affect the point that insurers (even if not actuaries) put a high price on this risk and that the price is subsequently suppressed by government insurance subsidies?
No, it is a realistic approach to a problem which has been facing many places elsewhere in the world where it has been solved using engineering. It is far more apt to call climate doom predictions statements of religious faith given the history of engineering solutions to climate-related problems and the close resemblance of climate doom preachers to those deriving their prophecies from scripture.
Here's a few books on the subject which might be of interest for those who want to widen their view on the ever-changing climate. All of them have in common that they do not deny the climate is changing nor that human activities influence how it changes. Where they differ from the doom narrative is that they approach climate change in the way humans have dealt with other environmental problems to lessen or negate their impact instead of by preaching some grand narrative on how society should be run to avoid catastrophe.
Apocalypse Never: Why Environmental Alarmism Hurts Us All by Michael Shellenberger
Thing is I figure you need some form of water board to manage it. A political entity that's all about "here we are and here we stay". Once they're set up they're pretty reliable (there's one that's still paying interest on a 370-year old bond https://www.youtube.com/watch?v=cfSIC8jwbQs )