The Furlo Pass: evolution of a landscape

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 The Furlo Pass in the territory of Pesaro Urbino is some sort of biological island.

It’s away from the Appennine – 20 km ish – and away from the hills too because of its 1000 metres altitude. Mountains and hills at the same time while the alluvial plains of Metauro and Candigliano river sip into its slopes.

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La Gola del Furlo, oggi | © Nicola Pezzotta 2011. All rights reserved.

The heart of this area is a big gorge where the Candigliano river flows 176 metres over sea level blocked since the first half of the last century by one of the most famous and spectacular dykes of central Italy. Rising the Via Flaminia from Fano towards Umbria through Calmazzo we find ourselves in front of the impressive gorge between Monte Paganuccio and Monte Pietralata. Along the old Flaminia road we can admire the great works men built inside the gorge, which significantly changed the surrounding view.

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La Diga del Furlo, oggi | © Nicola Pezzotta 2011. All rights reserved.

The barrage of Candigliano river (Furlo dyke) is the human work that most changed the inferior part of the Gorge in the last 80 years.  Previously in thousands or maybe millions of years the natural landscape was very different, and to realize that we need to look at the present day but also to observe carefully the pictures of the area between the nineteenth and the twentieth century.

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This postcard shows the Furlo Pass in 1870. The bed of Candigliano river was significantly narrower and deeper compared to the road level. | fonte: “Paesaggi Culturali”

The dyke has been built between 1918 and 1922 – exactly where a natural 10 metres fall was – by UNES in order to produce energy and then ENEL took it in 1962. At first the dyke stoked a station downstream the dyke on the Monte Paganuccio side (opposite the road), but it was destroyed during the second world war. The new station became active since 1952 and it’s located upstream Calmazzo on the left bank of Candigliano river. The basin can develop a power of 13000 Kw having 33.210.000 kWh producibility, which is the highest one in the Pesaro Urbino territory.

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Pulley used for the transport of the building material during the dyke construction. Please note the narrow bed of Candigliano river and the sides of Monte Pietralata and Paganuccio still overhanging. | fonte: “Paesaggi Culturali”

The dyke is built on living rocks, it’s 47 metres high and its shape is like an ark pointing the valley, after its “ark-gravity” category. So the most water load is distributed towards the lateral faces of Monte Paganuccio and Monte Pietralata. Like all the gravity dykes it’s thick on the base (16 m) while the top (where we can walk in case the dyke is open to visitors) is 3 m large. The barrage raised the level of Candigliano river along 3 km creating the artificial lake.

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The dyke work in progress | fonte: “Paesaggi culturali”

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Engineers building the dyke | fonte: “Paesaggi Culturali”

Dykes as human works normally influence extremely an environment which developed naturally for centuries or thousands of years. Many times these works are ecocompatible, but in a large number of cases and places these alterations are not acceptable; however these installations are built to produce clean and renewable energy, which is probably the best reward.

But even though the creation of a lake increases the biodiversity, the thing is that a place has been changed for good and it was the result of tettonic and hydrodynamic events that were going on along 200 millions of years.

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Building the ark dyke | fonte: “Paesaggi Culturali”

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Ark dyke | fonte: “Paesaggi Culturali”

The Furlo Gorge was really different in 1918: in the very place where the dyke is right now, we can easily gather (from the photos too) that the river originally flowed 60-70 metres deep compared to the present road. So the Gorge must have been more spectacular than ever. Just try and picture the river flowing between big rocks, rapids and falls.

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Vehicles transporting building materials | fonte: “Paesaggi Culturali”

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Candigliano after the dyke construction – upstream the dyke. The sides of Monti Pietralata and Paganuccio show little vegetation. The water level is significantly lower compared nowadays: infact we can see the old Roman constructions. | fonte: “Paesaggi Culturali”

Fishes like carps, barbus and chubs are now living in the basin. The shores are covered in carex, nettle, ivy, horsetail and Old man’s beard, as well as in trees like black and white poplar, white willow and wild fig. Sometimes we can even run into some mammals like wild boar, coypu or wild goats, and into birds like grey heron, night heron, swamp chicken, great egret and cormorant. Unfortunately the otter disappeared in the 50s due to an indiscriminate hunting.

In the next post we’ll talk about the central part of the gorge with its galleries. 

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