Arno River

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Arno River in Florence, Italy

The Arno is a river in the Tuscany region of Italy.

The river originates on Mount Falterona (1654 meters {5,426 ft}) in the Casentino area) of the Apennines, and takes a southward curve. The river turns to the west near Arezzo passing through Florence, Empoli and Pisa, flowing into the Tyrrhenian Sea at Marina di Pisa. With a length of 241 kilometers (149 miles), it is the largest river in the region. Its tributaries are : the Sieve (60 kilometers {37 miles}), Bisenzio (49 kilometers {30 miles}), Era, Elsa and Pesa.

It crosses Florence, where it passes below the Ponte Vecchio and the Santa Trinita bridge (built by Bartolomeo Ammannati, but inspired by Michelangelo). The river flooded this city regularly in historical times, the last occasion being the famous flood of 1966, with 4,500 meters³/second (158,916 ft³/s) after a rain of 437.2 millimetres (17.2 inches) in Badia Agnano and 190 millimetres (7.4 inches) in Florence, in only 24 hours.

Banks of the Arno, seen from the Ponte Vecchio bridge, Florence

Arno River in Pisa, Italy, near the Ponte della Fortezza

The flow rate of the Arno is irregular. It is sometimes described as having a torrent-like behaviour, because it can easily go from almost dry to near-flood in a few days. At the point where the Arno leaves the Apennines, flow measurements can vary between 0.56 meters³/second (19.8 ft³/s) and 3,540 meters³/second (125,013 ft³/s). New dams built upstream of Florence have greatly alleviated the problem in recent years.

A flood on November 4, 1966 collapsed the embankment in Florence, killing at least 40 people and damaging or destroying millions of works of art and rare books. New conservation techniques were inspired by the disaster, but even 40 years later hundreds of works still await restoration.^[1]