Venice, Italy is sinking. Once a military outpost in a marshy bay, it was built-out into its current form in north-northeastern Italy in the 10th century. If you’re not familiar with Venice, its wiki article is well worth a skim.
The city proper is incredibly beautiful, with unmatched architecture, streets of glistening water, and countless beautiful stone and brick bridges.
It costs Italy countless millions in taxpayer expense to maintain Venice. Already sinking into the muddy bay, the place is more threatened by climate related sea-level rise and ever stronger storms. Not only that, it’s falling apart at the seams. Sidewalks are cracked, there is no sewer system to speak of (waste is dumped directly into the water for the tide to take away), bridges are collapsing, and buildings crumbling. The city’s infrastructure is so old and constantly wet that it has its own construction crews who work non-stop patching the place up.
Two factors are exacerbating the flooding risk to the city: global sea level rise and subsidence. In short, sea is rising and the city is sinking. Like other cities built on river deltas, the sediment beneath the city is compacting over time. In a natural setting, this compaction would be offset by the deposition of fresh sediment at the surface, but the rivers feeding the lagoon were diverted in the 1500s. As a result, the land surface is sinking, and the salt marshes are suffering for it.
In my opinion, Venice should be scrapped, razed to the mud and turned over to the tidal marshes. Italy would do much better if it invested those endless millions into its school systems and preserving better works of art. History would forgive the Italians for being practical.
Of course, that would never happen. Venice will live on despite being such a monetary black hole.
A new paper by hydro researchers proposes a novel solution to help Venice survive - raising the city. Engineers would, if I’m reading this right, inject water into the mud underneath the city. The additional water would get trapped between tiny granules of sand, thereby expanding the land underneath the city. It would raise the city in some places, and stabilize in others.
Recently, another idea has been discussed. Just as withdrawing groundwater can cause subsidence, injecting water can reverse it. It’s not entirely a two-way street—much of the pore space lost during compaction can’t be recovered—but increased pore pressure can begin to unpack the sediment. Injection was used successfully in Long Beach, California in the late 1950s to halt subsidence caused by oil and gas extraction as well as groundwater usage. After the land surface dropped nearly 30 feet, injection stabilized the subsidence and a slight rebound in land surface elevation (a little over 30cm) was even seen in some spots. Early research indicated that a similar amount of uplift could be achieved in Venice, which could make a big difference for a city on the edge. The precision of those predictions was limited, however, by the lack of detailed knowledge about the layers of sediment beneath the city.
Read the rest at ars technica