The reclamation of the Val di Chiana

The Val di Chiana, mentioned as Clanis Aretinum by Pliny the Elder in his Naturalis Historia, is a valley that extends 60 kilometres from the Arno river near Arezzo to the north, up to the Val di Chiana Romana near Chiusi Scalo to the south. It occupies an area 15-20 km wide, which includes the municipalities of Chiusi, Chianciano Terme, Montepulciano, Torrita di Siena, Sinalunga, Foiano, Lucignano, Marciano, Monte San Savino, Civitella, Cortona Castiglion Fiorentino, Arezzo, Castiglione del Lago, Panicale, Paciano and Città della Pieve. It is crossed by the Canale Maestro della Chiana for about 50 kilometres and is bounded to the east and west by hills and mountains. Until the Roman era its entire length was covered by the river Clanis, today Chiana.

The Etruscans carried out the first work to regulate the hydraulic system in the area, to make the lands cultivable and the Chiana navigable up to the Tiber. The valley was for a long time kept so fertile and productive that it was known as the “granary of Etruria” until the end of the Roman age.

The water that flowed along the Clanis in the direction of the Tiber, with a limited gradient, received large quantities of untransportable material from the tributaries that ended up causing the whole area to be swamped.

During the Middle Ages, Orvieto, Arezzo, Perugia, Siena and Florence had to deal with the hydrogeological instability that had caused the progressive swamping of the area. Dante Alighieri, in Canto XXIX verses 46-49 of the Inferno, describes the valley’s unhealthy environment:

Qual dolor fora, se de li spedali
di Valdichiana tra il luglio e il settembre
e di Maremma e di Sardigna i mali

fossero in una fossa tutti insembre;

tal era quivi, e tal puzzo n’usciva
qual suol venir de le marcite membre.

The fragmentary nature of the interventions, caused by the precarious political stability that characterised the medieval period and the early Renaissance, was a significant obstacle to the necessary reclamation work.

The first intervention on the waters of the Chiana dates back to 1115, when they were routed through the Chiusa dei Monaci. Florence promoted this initiative to regulate the floods of the Arno, even though this intervention decisively caused the valley to be swamped.

In 1338 the first section of the Canale Maestro della Chiana was built in the Arezzo area to allow the waters of that area to flow towards the Arno: thus began the phenomenon of reversing the Chiana waters.

Between 1502 and 1503, Leonardo Da Vinci drew up, on commission from Cesare Borgia (il Valentino), a study of hydraulic arrangement for the region, which involved constructing a navigable canal along the Arno to Pisa that connected with Lake Trasimeno. The project, which had no luck with the Pisan opposition, foresaw the Val di Chiana functioning as a compensation basin in order to maintain constant water in the Arno. From the famous “bird’s-eye view” of Leonardo’s Val di Chiana, preserved in the Royal Library of Windsor in London, it can be seen that only at the mouth of the Arno up to Pieve al Toppo (about 14 km) did the hydrographic situation have a regular layout, while from Arezzo to Chiusi there extended an intricate swamp.

Only when all the territory came under the dominion of the Medici, with the fall of Siena in 1555, could an elaborated and complete reclamation plan be drawn up.

Under the Grand Duke of Tuscany Cosimo I, the excavation of the great collector already taking place on the Arezzo plain continued towards the south. The collector, which took the name of “Canale Maestro della Chiana”, reached the height of the ports of Cortona (near Foiano), moving the watershed back about halfway down the valley.

Further reclamation work on the valley commissioned by Ferdinando I de’ Medici moved the watershed to Lake Montepulciano (1599). On the reclaimed land were built the first large grand-ducal farms and the internal communication routes, indispensable for transporting agricultural materials.

In the seventeenth century the reclamation works stagnated due to technical, economic and political discord. Like Florence, even the Papal State, bordering the Grand Duchy of Tuscany at the south of the valley, was not favourable to executing the work, for fear that the swamp would undergo a shift towards Church State land.

Following the construction of a dam on the Astrone stream before its confluence with the Chiani stream, the waters of the Chiana rose up to partially submerge the tower of Beccati Questo in Chiusi, which was still surrounded by water in 1789.

In 1653 it was decided to begin work expanding and deepening the Maestro channel in order to avoid burial. While in 1664, coordinated interventions to regulate the waters between the Chiari of Chiusi and Città della Pieve were established between the Grand Ducal government and the papal court. Through the flood system of the hills, devised by Leonardo, the waters of the streams were conveyed in vast dammed areas so as to deposit the silt and the transported debris, raise the bottom and return clarified water to the Maestro channel.

Between 1703 and 1736, the watershed between the Chiana of the Tiber and the tributary of the Arno was officially defined at Chiusi, and the construction of the separation bank at this watershed.

In 1737 the reclamation work passed to the Lorena family, who made a concrete contribution to achieving the goal, framing the matter in a broad landscape of territorial politics.

In the second half of the eighteenth century, the Chiana was almost drained from the Chiusa dei Monaci (built in 1551) to the Callone di Valiano, with numerous ridges and marshy areas on the sides of the canal and ample uncultivable strips for grazing.

With Pietro Leopoldo, the reclamation work was included in the campaign in favour of the countryside, and involved all the work necessary to improve conditions for the inhabitants, carry out definitive rehabilitation of the valley, build internal communication routes and eliminate intermediate taxes.

In 1780 a concordat between Pietro Leopoldo and Pope Pius VI established regulation of the waters that flowed in the border area and the construction of an artificial bank on the hills of Chiusi between Chiusi Scalo and Città della Pieve. This was to separate the Val di Chiana Romana (today Umbria) to the south from the Val di Chiana Toscana to the north, putting an end to the conflict between the two states over reclamation work in the valley.

In this way the Maestro channel poured the waters of the basin into the Arno, including those of the Tresa stream that once belonged to the Trasimeno, already artificially conveyed to the Chiusi lake. While the Astrone stream flowed south, in Umbria, and entered the Chiani stream.

The work, conducted from 1789 to 1827 by Conte Vittorio Fossombroni from Arezzo, confirmed that in Val di Chiana there was no longer any need for work to make it fertile, but for coordinated maintenance work, in order to stabilise the conditions reached after two and a half centuries of reclamation. Fossombroni, a supporter of the reclamation method through “colmata” (filling), proposed giving the countryside surrounding the Maestro della Chiana channel a regular slope, to again lower the level of the Chiusa dei Monaci and the Callone di Valiano to increase the discharge of waters towards Arezzo. From 1838 to 1859 the work was overseen by the Florentine engineer Alessandro Manetti. After the unification of Italy, Carlo Possenti, an inspector from the Arezzo Civil Engineering Department, completed the work. The reclamation can be considered completed in the Fascist period.