Venice Offers Lessons on Coping with Rising Seas

Mose Project Aims To Part Venice Floods

Morning Edition,
NPR
January 7, 2008 ·

A boat ride in the Venice lagoon is a discovery of how humans and nature have created one the world's most extraordinary experiments.

Starting in the 16th century, the Venetians diverted major rivers outside of the lagoon to prevent silt from filling it up.

Left alone, lagoons like the one in Venice either tend to dry up and become land or they are overwhelmed by the sea and turn into bays.

The lagoon covers 212 square miles. Along with the city of Venice in the center, there are some 50 smaller islands, as well as dozens of mudflats and sandbanks — havens for thousands of aquatic birds that flock here even in winter.

This delicate and fragile ecosystem is the largest wetland in the Mediterranean.

If Venice is to be saved, the lagoon must be protected.

But today, rising seas threaten the Venice lagoon. All along the Grand Canal, windows of buildings near sea level have been closed and filled with cement.

"Those windows have been closed as they are too much exposed to the waters," says Francesca de Pol of Consorzio Venezia Nuova, the consortium entrusted with the task of safeguarding Venice.

Moving Upstairs

No Venetian lives on the ground floor any more.

In the last century, the city sank 11 inches, mostly due to the pumping of groundwater and methane gas for local industries. But it has also being affected by rising sea levels.

What that means is that the same tides that were not flooding the city 100 years ago are now high-tide events. It's called acqua alta.

High water afflicts Venice mostly in the winter. A century ago it happened seven times a year, now it's more like a hundred.

The visionaries who first began building Venice 1,300 years ago used materials for the foundations that could withstand water. But with the seabed sinking, brick walls on the ground floors are being corroded and waterlogged buildings are crumbling.

Sophisticated technology is now being used to rescue the lagoon. MOSE, the acronym in Italian for experimental electromechanic module, is the biggest public works project in Italian history.

MOSE is also the Italian word for Moses, recalling the biblical parting of the Red Sea.

The project is building 78 floodgates at the three inlets that link the Venice lagoon to the Adriatic Sea. Del Pol says one of the gates' characteristics is their flexibility.

Depending on the type of tides, there are differing ways to manage the gates.

"You are not obliged to close the whole lagoon," she says. "You can close one inlet and not the other.

"In case of wind coming from a certain direction, you can chose not closing the whole system but only parts of the gates for certain types of tides.

"So you continue to have an exchange of water, not totally blocked."