The purpose was to decrease the floods which sometimes threaten to entirely submerge the city.
During floods they pour over their banks upon the surrounding valleys, by a thousand channels which interlace and establish communication between the main streams. After numerous bifurcations they find their way into the sea by three principal mouths.
It was close to water but high enough to escape floods.
For the next sixty years an urgent question was the prevention of floods in the capital.
The country was also visited by a succession of famines and floods, and in 1348 the Black Death swept over Europe like a terrible scourge.