Are you prepared? - Large dams risk

Sei preparato Rischio grandi dighe

Knowing the risks to which large dams can be subjected is the first step to learn how to handle any emergency situation in the most correct way. In this section we report on the correct actions to take in the event of flooding downstream of a large dam.

The flooding downstream of a dam is preceded by specific alert phases during which the National Civil Protection Service is activated.
In some cases, the period for warnings may be so narrow that it is impossible to warn the population. Therefore, it is essential to know:

  • if the municipality where you live, work, or stay is downstream of a large dam and, in particular, if the area where you are located is at risk of flooding
  •  in the proximity of watercourses, downstream of large dams, signs are generally placed warning of areas potentially exposed to the danger of flooding due to spillway operations
  • in the event of a large dam collapse, an IT-alert message will be sent to the population residing in municipalities downstream of the structure that could be affected by the flood. Remember that the IT-alert system has some limitations. For more information, go to
  • each large dam is equipped with an acoustic siren activated to warn people of the occurrence of a flood wave, following the activation of spillway operations
  • during a flood, water can rise suddenly, even by one or two meters in a few minutes
  • some areas flood earlier than others due to their proximity to the dam and the watercourse
  • at home, the most dangerous areas are basements and ground floors; outdoors, underpasses, areas near embankments and bridges, highly steep roads, and generally all areas lower than the surrounding area are most at risk
  • the power of water can also damage buildings and infrastructure (bridges, rockfill platforms, embarkments), and the most vulnerable ones could suddenly fail or collapse
  • the safety of a building depends on many factors, for example, the type and quality of materials used in construction, the altitude at which it is located, the distance from the large dam and watercourse, the number of floors, and the more or less direct exposure to the impact of the wave.

If you live, work, or stay in an area at risk.

  • Find out about the municipal Civil Protection Plan to find out what flood risk areas, escape routes, and safe zones are in your city
  • If you have any doubts about the safety of your home, contact an expert technician

Suppose you are located in a municipality downstream of a large dam, and there is an alert for "collapse" or for the activation of spillway operations. In that case, the area may be affected by a flood. In the first case, an IT-alert message will be sent; in the second, you may be warned by acoustic sirens or other warning systems provided by the municipality. In both cases, civil protection authorities may indicate that you should temporarily evacuate your home or give you other information on what to do. In the absence of specific indications, remember:

Outdoor, near a watercourse downstream of a large dam

▪ Reach the highest nearby area quickly.
▪ Move away from the flooded area: due to the speed at which water flows, even a few inches could make you fall.
▪ Avoid using a car. Even a few inches of water could make you lose control of your vehicle or cause it to shut down: you risk being trapped.
▪ Avoid underpasses, embankments, and bridges: stopping or passing through these places can be dangerous.
▪ Warn people around you of the upcoming danger.
▪ Limit cell phone use: keeping the lines clear makes it easier for rescuers.
▪ Keep informed about the situation and follow instructions given by authorities.

If you are indoor

▪ Go upstairs if you are in a basement or on the ground floor. Avoid the elevator: it can be stuck.
▪ Do not enter basements or garages to secure possessions: you are risking your life.
▪ Do not go outside at all to secure your car.
▪ Help older people and people with disabilities who are in the building.
▪ Do not drink water from the tap: it may be contaminated.
▪ Turn off the gas and electrical systems. Do not touch electrical fixtures with wet hands or feet.

  • Follow the authorities' instructions before taking action, such as re-entering the house, shoveling mud, emptying water from cellars, etc.
  • Verify if you can get your gas and electrical systems back on. If necessary, seek advice from an expert.
  • Before drinking tap water make sure municipal ordinances or notices do not forbid it; do not eat food that has come in contact with flood water, it may be contaminated.
  • Ensure sewers, septic tanks, and wells are not damaged before using drains.
  • Do not travel along flooded roads: there may be sinkholes, potholes, open manholes, or sheared electrical wires. Also, the water could be contaminated with fuels or other substances.
  • Also, pay attention to areas where water has receded; the road surface could be weakened and collapse.