Intervention to stabilise and make unsafe the right slope of the Casanuova dam reservoir and intake works on the Chiascio river

The Casanuova Dam on the Chiascio River, located in the municipality of Valfabbrica, supplies 145 million cubic metres of water per year, meeting the drinking water needs of Perugia and other Umbrian cities and irrigating approximately 65,000 hectares. With a basin of 471 km² and a lake of over 20 km, it stores up to 224 million cubic metres of water, usable for various purposes, including civil, industrial and ecological uses, with a multi-year and multifunctional regulation capacity. Due to a deep gravitational movement of approximately 18 million cubic metres involving the right bank of the Chiascio River near the dam, it was necessary to design safety measures for the reservoir. The solution chosen is a bank stabilising the right bank, extending the entire width of the valley bottom, from the Fosso di Sambuco to the side of the dam. The site’s hydraulic vulnerability conditions were assessed through detailed 2D hydraulic modelling on the Chiascio River, analysing an 18 km stretch that includes the planned quarry areas. The simulations examined both the safety of the various work areas and the effectiveness of the temporary tura and maxitura structures, considering runoff scenarios with return times between 4 and 20 years and crest heights at 282.50 m and 286.50 m, using the FLO-2D software.