AN ASSESSMENT OF THE 1966 FLOOD OF THE ARNO RIVER, FLORENCE, ITALY, FROM NEW MAPPING OF HISTORICAL DATA

The Florence basin in Italy has a great history of floods throughout the area, the most famous example being the 1966 flood of the Arno River on 3-4 November which resulted in 112 deaths, left thousands homeless, and destroyed or damaged a great amount of art. The Arno River is ~240 km long and drains an area of~8230 km², all of which located is Tuscany, Italy. It flows from the Mount Falterona hills of the Apennine Mountain range to the Ligurian Sea. The seasonal rains during the fall months account for the excessive flooding the city of Florence has experienced throughout its inhabitance. Florence is affected by various climatological and physiographic factors that result in these very large floods, which also devastated the city in 1333, 1557, and 1844. Flooding in the Florence basin can be contributed to both the orography of the Apennines, which correlates to the high run-off rates as well as river discharges, as well as the unique urban development of downtown Florence, which resulted in worse flooding and greater damage east of Ponte Santa Trinita than west.

After the 1966 flood of the Arno the city of Florence placed permanent flood markers around the downtown area to show the extent and depth that the flood reached throughout its duration. We collected GPS and elevation data based on these flood markers in order to map the extent of the 1966 flood. The data collected in Florence has reveled that the reasoning for the unique flood pattern of the downtown area is a result not mainly from topographic features but the anthropogenic influence of the structures that run along the Arno river. The most intense flooding occurred east of the Ponte Santa Trinita in the center of Florence. In order to understand why the flooding happened in this way we analyzed the urban structures that run along the Arno River. The buildings to the East of Ponte Santa Trinita and past Ponte Vecchio were constructed directly on the shore and brace the river itself. The architecture of the buildings on the Eastern side of the Arno river created a man made flood wall. Because of this the heaviest flooding took place to the West of Ponte Santa Trinita thus heavily flooding the downtown area of Santa Croce. The maps we have created show the extent of the data collected as well as an accurate reflection of our hypothesis.