Dr Sonia Fortuna is a Senior Dam Safety Engineer at Goulburn Murray Water, with over 20 years of professional experience. She is passionate about dams and the value water, as a scarce and precious resource. She has geotechnical engineering background, having experience in the academia – with a PhD focusing on soil mechanics and advanced laboratory testing – as well as in geotechnical engineering design with a variety of applications, besides the water sector. She was a past Peer Reviewer for Géotechnique and the Journal for Geotechnical and Geoenvironmental Engineering ASCE. She is a Division Committee member of Engineers Australia in Victoria (starting in January 2024). Besides water and dams, she is passionate about the engineering community, diversity, innovation – and, more recently, house restorations.

Presentation Title: GMW special dam safety inspections following the 2022 Victorian floods

Abstract: Goulburn-Murray Water (GMW) own or manage 15 large dams, from Significant to Extreme consequence category. While it is unexpected that GMW storages are affected by floods every now and then, the 2022 floods were uncommon, in that they affected the entire region and all GMW catchments, and storages. Both the flows and lake levels were well within the design criteria for each storage. However, due to inevitable limitations and unknowns in design, heightened surveillance and monitoring are warranted well before – and below – critical conditions are reached.

A number of GMW storages experienced historic high inflows, and some reached new historic high storage levels that tested them into “unknown territory” from a dam safety perspective (although they were safe, from a pure design perspective).

Quick dam safety decisions had to be made, such as whether to heighten surveillance where some unexpected event occurred – such as increased seepage or movements – while balancing demands on GMW storage operators, who were already impacted by demanding flood operation activities
and rosters.

Where historic high storage levels were experienced more frequent surveillance and reporting activities were well supported by storage operations staff.

As soon as the road access, weather and the lake levels allowed, GMW Dam Safety team inspected a large number of our storages, arranged on a risk basis, i.e. typically where pre-existing conditions warranted some level of increased risk mitigation measures. These Special Inspections focused on specific elements of each storage that may have been affected by the floods, such as the spillways. The inspections included Waranga Basin embankment, Dartmouth Dam spillway cascades and chute, Lake Eildon Spillway; Laanecoorie Primary and Secondary Spillway; Torrumbarry Weir; Lake Eppalock Primary and Secondary Spillways; Goulburn Weir; Tullaroop Secondary Spillway; Mildura Weir (trestles reinstatement).

Damages were systematically documented, and consequent recommendations for remedial actions informed GMW flood recovery works. During this presentation we will share some key findings from our Special Dam Safety Inspections.