The Ruins of Gleno Dam

In a small valley, among the mountains of Lombardy, in northern Italy, stands a dam, or rather, half a dam. Built on the Gleno Creek, the Gleno Dam was supposed to provide hydroelectric power to the region, but because of shoddy construction, the middle section of the dam collapsed after the reservoir was filled, leading to huge destruction along the downstream valley and the death of over 350 people. The wide gash in the dam is still visible to this day.

Gleno Dam

The Gleno Dam with its gaping hole in the middle. Photo: Giacomo Feroldi/Shutterstock.com

The Gleno Dam is located in Valle del Povo, a small subcatchment in Valle di Scalve in Lombardy. The dam’s original approved design was of masonry gravity, but midway through construction, because of lack of funds, it was changed into a reinforced concrete structure of the multiple-arch type. The multiple arch dam was constructed on top of the gravity dam foundation. The dam was 220 meters long and 46 meters high.

In the early morning of December 1, 1923, about 40 days after the first complete reservoir filling, an 80 meter long section of the dam collapsed, causing a mass of water to sweep downstream up to 21 kilometers away destroying three villages, five power stations, countless bridges and a number of isolated buildings and factories. The death toll was 356.

Investigation revealed that the concrete used in the arches was of a poor quality and it was reinforced with anti-grenade scrap netting that had been used during World War I. There were also indications that the dam was poorly joined with its foundation, and that the concrete was not completely cured when the reservoir was filling. As a consequence of this catastrophic event, the multiple-arch design, although in itself not responsible for the accident, was almost completely abandoned in Italy.

The collapsed dam still stands on the site as a chilling reminder to the tragedy.

Gleno Dam