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on top of the spillway “was not a very smart idea”. However, it wasn’t the main problems because the flood wave was much larger than the capacity of reservoir, the structure of the spillway and footbridge obstructed debris, with small gates failing to prevent clogging of the bottom outlets. In conclusion, Radzicki says Poland needs verification of the discharge capacity of existing hydrotechnical structures for present catastrophic flows, giving consideration to climate change predictions. And if necessary, they need to reconstruct or expand the discharge facilities and adjust reservoir operation policy accordingly.
Communications also failed during the Stronie dam
failure. GSM telephone service in the region collapsed and other means of communication were inadequate. This meant the warning about dam failure did not reach affected communities and so a nationwide review of disaster response communication systems is necessary. In Poland dams are classified from Class l (most important) to Class IV (least important). The Stronie Dam is a Class III. The failure of this 120 year-old dam demonstrates that even ‘smaller dams’ can pose catastrophic threat to nearby towns. “Considering the unsatisfactory technical condition of many dam structures in Poland, it was largely a matter of luck no other dam disaster occurred besides the failure of the Stronie Dam,” Radzicki said. Looking back over the September 2024 flood event, Radzicki concluded: ● Large flood control reservoirs over 100Mm3
, such
as Raciborz Dolny or Goczalkowice, are crucial for flood protection of vast areas of the country and they fulfilled this role.
● In mountain catchments only systems of smaller reservoirs can provide an effective reduction of flood risk.
● Communication and warning systems for natural and technical disasters including dam failures must be verified and if necessary improved.
● The development and implantation of modern systems and methods and methodologies for testing, monitoring and forecasting precipitation, rainfall runoff transformation, flows and dam performance are key to minimising flood risk and optimising repair and modernisation of damming structures.
Italian experiences Rinaldo Murano, from the Italian Ministry of Infrastructure
and Transport, spoke about the Vaia Storm which struck the country from 26-30 October 2018. An extreme weather event that affected the northeast, it brought extremely strong winds and persistent rainfall which saw millions of trees fall, constituting a huge natural disaster. At the Comelico Dam thousands of trees nearby were swept into the reservoir, and the heavy and abundant rainfall caused the Piave and Brenta rivers to overflow. In the mountain areas, several streams burst their banks and many landslides occurred. A dam able to mitigate the impact of the flood was the Ravedis Dam on the Chelina River. Built for the primary function of flood control, it also has additional functions of regulating flow for irrigation, plus hydropower production. As Murano explains, the incoming flood wave had two peaks, with the outgoing peak having a reduction of about 42% which helped to prevent many towns downstream from possible new floods. “The presence of a dam can have an important function for the hydraulic defence of downstream
territories. Any intervention aimed at reducing dangerous conditions downstream, through hydraulic systems interventions of the watercourses and maintenance of hydraulic works and or riverbeds, are also useful,” Murano said. “It is also important to take climate change into account. From a hydraulic point of view we mut be able to evaluate and prevent such changes,” he added.
Under pressure Catalin Popesc, Technical Director at Aquaproject and a
lecturer at the University of Civil Engineering in Bucharest, talked about the operational lessons learnt from the July 2025 Bistrița–Neagra flash floods in Romania. Following intense rainfall in the upper Bistrita
catchment there was a rapid rise in river levels, flash floods and slope instability. In Suceava County in the Brosteni area there were violent flood waves in small and medium catchments and water levels exceeded known historical marks. Massive transport of wood, debris, vehicles and coarse sediments occurred with blockages at bridges and culverts leading to sudden dam break waves amplifying destructive forces. Over five days three people died, more than 300 people
were displaced and 111 evacuated by helicopter. More than 200 homes destroyed and thousands damaged region wide. There was also disruption to water supply and electricity, and agricultural land was inundated with losses in crops and hay reserves. Emergency measures included evacuations, temporary shelters, reinforcements of riverbanks and restoration of access roads. Estimates suggest more than 100 million euros of damage occurred. At the Izvorul Muntelui Dam, a 75 year-old concrete gravity dam on the Bistrita River which is of ‘exceptional importance’ producing 435GWh year and flood mitigation, it took one and half months to get wood debris from the reservoir. Popesc said the outcomes of this extreme event could have been avoided if a flood mitigation reservoir existed. A non-permanent flood control reservoir upstream of Brosteni would cost about 12 million euros and would have sparred everything that happened there with minimal losses, he claims. He gave the example of a 35m high dam designed for temporary retention and able to attenuate peak flows of 250-400m3
/sec (as in the July 2025 flood).
The effect would have been to store/attenuate around 90% of the flood volume, prevent destruction of 200 homes and local infrastructure and avoid losses of around 90 million euros (nine times the investment return).
Above: House destroyed by floods in Brosteni, Suceava County in Romania. During 2025.
Esin Deniz/
Shutterstock.com
References
Recording of the webinar organised by EURCOLD and ICOLD YPF on Mitigating Flood Risk: The Strategic Role of Dams in Europe, held on September 30, 2025.
https://www.youtube.com/ watch?v=UZoqLaAo5dM
www.waterpowermagazine.com | May 2026 | 17
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