Leonardo da Vinci: rivers, water, science and art (Part 3: diverting the Arno)


Leonardo da Vinci, Landscape drawing for Santa Maria della Neve on 5th August 1473. Licensed under Public domain via Wikimedia Commons

In my previous posts on Leonardo da Vinci, I described his fascination with water and rivers, which pervaded his art and his science. Leonardo is rare amongst artists, then and now, in his combination of art, science and engineering. He, like many of those who did not come from the nobility, had to secure an income and so was always on the look-out for a generous patron. But he clearly also had an intense curiosity in almost every field of endeavour. The scope of his interests and work was staggering. Leonardo took on a variety of roles and had a number of influential patrons: as artist and engineer for Ludovico Sforza, duke of Milan; as architect and military engineer for Cesare Borgia, Pope Alexander VI’s son; as architect and hydrological engineer to the French governor, Charles d’Amboise, once again in Milan; as scientist, mathematician and hydrological engineer in Rome to Giuliano de’ Medici, brother to Pope Leo X; and as philosopher, artist, scientist, architect, technical expert and ‘ornament’ at the court of Francis I, King of France, where Leonardo died in 1519. But it was while living and working for the city of Florence, near his birth place of Vinci, in the late 1400s and early 1500s, and specifically his association with Niccolò Machiavelli, the politician, philosopher, historian and writer, and their combined attempts to divert the River Arno from Pisa, to deprive that city of water and create a seaport for Florence, that I want to turn now. It’s a great story.

LEONARDO. Licensed under Public domain via Wikimedia Commons.

LEONARDO. Licensed under Public domain via Wikimedia Commons.

Niccolo Machiavelli's portrait by Santi di Tito. Licensed under Public domain via Wikimedia Commons.

Niccolo Machiavelli’s portrait by Santi di Tito. Licensed under Public domain via Wikimedia Commons.










First a bit of Italian history. In the 15th Century, Italy was unlike it is today. Instead of one country, governed from Rome, it comprised a number of independent states which were at times at war with each other and at others, suffered fragile treaties and alliances. The states included the Papal states, ruled by the Pope, the kingdom of Naples, the duchy of Milan and the republics of Florence and Venice.

During the Renaissance, the arts and sciences flourished like they hadn’t since ancient times. This was no more evident than in Italy, where many of the best known artists (think, for example, Raphael, Botticelli, Michelangelo) lived and worked. Many of the city republics at that time struggled to govern themselves, because of internal disagreements and frequent coups and stratagems, and so became, in many cases, ruled by tyrants. Milan, for example, was one of the richest and most powerful cities and was ruled by the House of Sforza from the mid 1400s for about a century.

Florence was another important city and, while outwardly a republic, and with several groups of citizens – eight Signoria, one Gonfaloniere, twelve Buonomini, sixteen Gonfalonieri and others – contributing to decision making, it was pretty much ruled on-and-off by the Medici family (who, incidentally, provided four popes) for more than 150 years1. Truth, as they say, is stranger than fiction, and George R.R. Martin could well get inspiration for his books from the alliances, betrayals, conspiracies, battles, assassinations and, yes, lusty behaviour, of the people in Renaissance Italy.

Anyway, there had long been enmity between Florence and Pisa, principally because Florence had wanted control over Pisa, because it had a Mediterranean seaport at the mouth of the Arno, and sea trade was the water-way (ahem) to success, prosperity and riches. But Pisans wouldn’t have it. In 1406, Florence was in control of Pisa. But in 1494, at the request of Ludovico Sforza, duke of Milan, the French invaded, took Pisa and gave it its independence from Florence. The French withdrew from Italy in 1498, and Florence began their long assault on the city, unaided by the French or Venetians, who weren’t happy about it but who had other fish to fry.



Around this time, Niccolò Machiavelli, as second chancellor in the Florentine government, was acting as emissary on several missions to other states. In 1502, Leonardo spent a period as architect and military engineer with Cesare Borgia, the current Pope’s son, who as commander of the papal armies, was busy conquering cities in northern Italy, trying to make a name for himself and becoming unpopular in the process. Machiavelli was, for a time, Florence’s emissary to Cesare Borgia. It is not certain if Leonardo and Machiavelli met at that time, but this is what has been speculated by historians. It is also thought that Leonardo might have been operating as a Florentine spy, because Machiavelli failed to mention his name in dispatches, despite being in the same town at the same time and despite Leonardo’s fame.

Not long after, Leonardo returned to Florence, and we know that Machiavelli and he were working on ways to defeat Pisa. Many assaults failed and the frustrated Florentines were becoming impatient to conquer Pisa once and for all. Around that time, Leonardo made several maps and sketches of the Arno River and its valley and was clearly studying the layout, and anticipating the task ahead. In fact, the idea about diverting the Arno and making Florence a seaport had been on his mind for many years.2

By mid 1503, Leonardo was at the military camp outside Pisa, acting as an hydraulic engineer, with the job of working out how to deprive the Pisans of the river that flowed through their city. Machiavelli, along with Piero Soderini, then head of state (Gonfaloniere), were both great supporters of the idea, despite widespread skepticism from many in the Florentine government. It seems that seventy years previously, an attempt to flood the nearby city of Lucca had failed miserably, and memories of that failure still rankled. But, Machiavelli recognised that there was a big difference between using a river to flood an enemy, and diverting it to deprive it of water.

Leonardo had many ideas involving the Arno and the potential for Florence to have its own seaport. This included straightening the river at Florence, which would have meant potentially digging a tunnel under a mountain pass! There were also several options for diverting the Arno at Pisa: one draining the river to a marsh, the Stagno di Lavorno; the other draining it direct to the sea. Added benefits of the diversion were for the irrigation opportunities it would bring.

In late 1503, Machiavelli was in Rome to lobby for the election of a new pope, while Leonardo, back in Florence had been commissioned to paint a mural in the Great Council Hall, opposite a fresco by Michelangelo, who had just finished his statue of David.3  It is thought that Machiavelli got Leonardo the commission. In early 1504, the siege of Pisa was proving problematic, the need for many additional troops to take the city was evident and threats that Florence was at risk of invasion by the Spanish surfaced. Finally, the governing men of Florence agreed that the only way to take Pisa was to divert the Arno. In fact, the Pisans were more worried about this than other potential approaches to bring them to their knees. By August of that year, we know that Machiavelli had appointed a commissioner and engineer to oversee the work.

Two channels were to be dug from the Stagno di Livorno and converge at the Arno. A staggering one million tons of earth was going to have to be shifted. Leonardo did all the calculations on how wide and deep the channels had to be, how many men were needed to dig the channels and how long it would take. He also designed a weir next to the Arno, behind which the channel was dug, which would have to be lower than the bed of the Arno, so that when the weir was removed, the river would flow of its own accord into the new channel.

Leonardo's drawing of the Arno and the weir alongside.

Leonardo’s drawing of the Arno and the weir to be built alongside to prevent water flowing down the new channel.

Unfortunately, the hydraulic engineer chosen to oversee the construction of the channels, one Master Colombino, was by all accounts ineffectual and did not follow the plans that Leonardo had so carefully devised. He dug two channels all the way from the Arno to the Stagno di Livorno, instead of combining them at the junction with the Arno, he underestimated the time it would take and the number of workers needed, and, disastrously, dug the channels shallower than Leonardo had determined.

Machiavelli was concerned about these changes and expressed them in writing, initially tentatively, and then more forcefully, as he realised that if you want to divert a river, the fundamental requirement is that the new channel is deeper than the old! And sure enough, the river had only just begun to flow into the two channels, when it when back to its old course and some of the earthworks collapsed. Despite the setback, it was decided to proceed, even though the number of workers was insufficient. Commands were given to protect the works from the Pisans while also widening the second channel. And then, to top it all off, there was a sudden, heavy downpour of rain from a storm, and the walls of the channels started collapsing. Finally, when the Florentines let down their guard, the Pisans stole in, demolished the weir on the Arno and filled in the channels.  And that was that.

The attempt to divert the Arno and defeat the Pisans failed miserably and Leonardo and Machiavelli went on to other projects.  Leonardo continued and expanded his interest in water, rivers, canals and hydraulics in the various cities in which he later lived, although he was known primarily for his genius as a painter and died in France in 1519. Machiavelli’s tumultuous career took numerous twists and turns, but resulted in one of the western world’s most famous works on political philosophy, The Prince, which established its writer’s place in history. He died in 1527 in Florence.

But what of Florence and Pisa?  Machiavelli did finally assist Florence in taking Pisa in 1509, after he was instrumental in establishing a people’s army.

Notes and references

1Much of this narrative has been gleaned from Roger Masters’ excellent Fortune is a River: Leonardo da Vinci and Niccolo Machiavelli’s magnificent dream to change the course of Florentine history. 1998. The Free Press, New York. I encourage anyone interested in this fascinating period to get a copy. You won’t be disappointed.

2He had also begun working on the Mona Lisa during this period.

3 The Battle of Anghiari was never finished and now lost.

Additional information on Leonardo da Vinci was from: Kemp, M. 2006. Leonardo da Vinci: The Marvellous Works of Nature and Man, Oxford University Press; on Machiavelli, Italy, Florence and Pisa was obtained from Collier’s Encyclopedia 1982. Macmillan, Canada; and Wikipedia.














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2 Responses to Leonardo da Vinci: rivers, water, science and art (Part 3: diverting the Arno)

  1. Pingback: Leonardo da Vinci: water, rivers, science and art (Part 1) | River Ecology and Research

  2. Pingback: Leonardo da Vinci: rivers, water, science and art (Part 2: his paintings and rivers) | River Ecology and Research

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