Modern satellites are helping scientists monitor how quickly Venice — the “floating city” of romance — is sinking with an unprecedented level of resolution.
The results show the city is naturally subsiding at a rate of about 0.8 to 1 millimetre per year, while human activities contribute sinking of about 0.08 to 2 to 10 mm per year.
Researchers said the sinking threatens to increase flooding in Venice, which already occurs due to high tides about four times per year.
The satellite data has revealed the amount that Venice is sinking, allowing scientists to compare the influence of natural causes of the sinking, due to compaction of the sediments on which the city is built, and to man-made ones, such as building restoration.
Understanding how the land is sinking is particularly important in the face of rising sea levels.
“Venice is in a situation so critical with respect to the sea that continuous monitoring of the city’s movement is of paramount importance,” said researcher Pietro Teatini from the University of Padua in Italy.
Scientists first recognised the problem decades ago when they noticed 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, ‘LiveScience’ reported.
Researchers 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.
The second one came from a newer satellite with sensors that have much better resolution and take measurements every 10 days, the report said.