Dam safety management

The greater the damage a dam could cause if it were to fail, the more effort a dam owner needs to put into monitoring it.

Larger dams have safety plans which include regular inspections by experienced and qualified people, and monitoring of instruments installed at dam sites. Information from such instruments is collected regularly and the dam safety managers are continually looking for signs of change in their dams.

Dam owners also prepare operations and maintenance manuals with instructions on how to operate the dam under many different conditions, such as during a large flood.

While Victoria’s dam safety record is good, some of our older dams were built as far back as the 1860s. Although these dams were constructed to the best standards of the day, design standards have improved over time, as we gain better knowledge on storms, earthquakes and construction techniques.

As standards improve, dam owners assess their dams for risks and identify work that can be done to improve safety.

All large dams, or dams with potential to cause significant damage if they fail, need to have a Dam Safety Emergency Plan. This plan guides the dam owner's response to an unwanted situation at the dam. Testing the plan with emergency service organisations builds trust and an understanding of everyone's responsibilities in the unlikely event of a dam safety emergency.

The Emergency Management Manual of Victoria assigns roles to emergency service organisations and other agencies for types of incidents.

In a dam safety emergency, the dam owner, along with DELWP, manages response activities to minimise the impact on the community and the environment from the incident.

If warning or evacuation is needed, the State Emergency Service (VICSES) and Victoria Police are involved. Local councils provide emergency relief to the community.

Visit the Emergency Management Victoria website

While it is highly unlikely that a well-constructed and maintained dam would fail, such a failure that causes serious damage to the structure is called a dam break. This extremely rare event can occur by:

Overtopping

During a flood, water that cannot be stored or controllably released, overtops the dam. Dams made of earth or rock can erode and fail quickly if overtopping continues to occur; or

Structural failure

The chance of a dam break happening is very low. If a break were to happen the flooding associated with such a situation would depend on the height of the dam wall, the amount of water in the dam and the shape of the valley below the dam.

Flood engineers make predictions of the flow paths and levels of the released water and plot them on maps known as 'inundation maps'. These maps are useful in planning for the impacts of a potential dam break scenario since the inundation maps give some indication of the flow path. However, the actual flood can be different as these maps are based on assumptions of how the dam will fail, which is difficult to predict.

The path of water during the flood can also be difficult to predict as erosion or blockages by debris can change the course of the flood.