The Floating city-Venice is sinking!
Saturday 30 November 2013

The Floating city-Venice is sinking!

Venice, the "floating city" of romance and gondolas, is really going to float. A new study data states that Venice is sinking with a n exceptional level of resolution, and the reason for this natural disaster is “the human”. Due to compaction of the sediments on which the city is built, versus man-made ones, such as building restoration.

Map of the displacement rate (mm/yr) detected at Venice by satellites from March 2008 and January 2009, including popular tourist destinations around the city. Negative values indicate settlement, positive mean uplift.

A study researcher and a hydraulic engineer at the University of Padua in Italy.  Pietro Teatini said “Venice is in a situation so critical with respect to the sea that continuous monitoring of the city's movement is of paramount importance.

It was acknowledged decades ago by the scientists that pumping of groundwater from beneath Venice was causing the city to settle into the earth. The pumping and its effects have long since stopped, but the city continues to sink.

In the study, Teatini and his colleagues used two sets of satellite measurements of Venice's historical city center and the surrounding area. The first dataset came from first-generation satellite sensors that have coarse resolution and collect data about once a month, whereas the second dataset comes from a newer satellite with sensors that have much better resolution and take measurements every 10 days.

"The techniques are continuously evolving and improving, and we are able to detect displacement with an accuracy that was unbelievable 10 to 20 years ago," Teatini told.

The satellites beam signals down to the Earth's surface, where they reflect off land and buildings. To determine the amount that Venice is sinking, the researchers measured differences in the signals returning from the city relative to those returning from nearby areas, a method called interferometry.

Teatini's team compared short-term changes in the city's height measured by the new satellite from 2008 to 2011 with the average, long-term movement measured by the old satellite from 1992 to 2010. Then they subtracted the short-term changes in ground level from the long-term ones to determine the human contribution to the sinking.

The results revealed the city is naturally subsiding at a rate of about 0.03 to 0.04 inches (0.8 to 1 millimeter) per year, while human activities contribute sinking of about 0.08 to 0.39 inches (2 to 10 mm) per year. However, human activities, such as conservation and reconstruction of buildings, cause sinking only on a localized, short-term scale, the researchers said.

Teatini documented the proofs and presented this already. Venice isn't the only city that's sinking – parts of New Orleans are dropping at a rate of 1 inch, or 2.5 cm, per year, possibly due to the removal of oil, gas and water from underground reservoirs, studies suggest.