Saline Injections for Venice?
Venice is sinking. It’s sinking due to tectonic forces, being on the wrong side of the plate flexure that’s lifting the Alps. It’s sinking because in the 16th century they diverted all the rivers around in an effort to avoid floods, thereby depriving the lagoon of the influx of fresh silt to which it had been accustomed. It’s sinking because that’s just what happens when you put a bunch of heavy city on top of soft sediment. It used to be sinking because people were pumping water from the aquifers beneath it, but that mostly stopped in the 70s. This has caused all the problems you might expect when an entire city sinks into the freaking ocean.
A group at the University of Padua is working on a scheme that could, if successful, raise the entire city by 25-30cm in about 10 years. The idea is to do the opposite of what mid-20th century industry and agriculture did to the city, and pump water into an aquifer underlying the city. They’ve just published their plans for a pilot project in Water Resources Research*.
Thirty centimeters is not enough to fix everything – high tides flood the city with a meter to a meter and a half of water on a regular basis, and projected sea level rise in the Adriatic could add another half meter onto that in the coming decades. But every little bit helps, reducing the area of the city that requires expensive pavement-raising procedures and adding just a little more margin of safety to the system of mobile flood gates and levees. By inflating deep aquifers, it’s also possible to lift areas of the city, like the Piazza San Marco, where the historical architecture makes it unfeasible to just add more dirt to the top**.
Of course, publishing plans for a pilot project in an academic journal is rather a long way off from actually implementing a city-wide intervention. I’m not sure what level of political or financial backing the idea is getting from Venetian authorities – the official site devoted to explaining what the government is doing about the floods (which I highly recommend as a great example of public outreach and geo-engineering porn) doesn’t seem to mention it. But even if this doesn’t happen in Venice, there are plenty of coastal cities around the world that could use a lift up.
*Castelletto, N., M. Ferronato, G. Gambolati, M. Putti, and P. Teatini (2008), Can Venice be raised by pumping water underground? A pilot project to help decide, Water Resour. Res., 44, W01408, doi:10.1029/2007WR006177.
**Rather than a lift, the Piazza San Marco is getting new embankments and an elaborate drainage system – see here for details and groovy technical diagrams.