Scrivener Dam Dissipator Strengthening Project

Update 17 September 2021

The physical hydraulic model project is now complete. The modelling found, under certain flow conditions, that the downstream structure of the dam dissipates the energy of the water flowing over the flood gates, with the structure experiencing unusual loading conditions.

We are using the outcomes of the modelling to undertake design for strengthening of the dissipator of the dam. The concept design has commenced and should be completed by late October 2021. It is expected that a major project to strengthen the downstream structure of the dam will be completed in future financial years.

Scrivener Dam works and model dam

Scrivener Dam holds back the Molonglo River to form Lake Burley Griffin (The Lake). The Lake is the centre piece of the Nation’s Capital and is heavily used for a wide range of recreational and commercial activities. The dam has three low level outlets (sluice gates) and five “fish belly” flood gates that allow for precise control of the water level in the Lake. The dam also functions to control floods and reduce damaging erosion downstream. The total discharge capacity of the flood gates is 8,500,000 litres per second – that’s almost three and a half Olympic swimming pools every second!

A scheduled design review in 2016 highlighted the need to investigate hydraulic pressures downstream of the dam during flood events.

Earlier this year in 2020, the National Capital Authority (NCA) worked with the University of New South Wales Water Research Laboratory (UNSW WRL) to design, construct and test a scale model of Scrivener Dam. The model was used to better understand how the dam and its environs function under a range of operational scenarios. 

David Wright from the NCA explains in this video:

Laura Montano from UNSW WRL explains in this video:

Ben Modra from UNSW WRL explains in this video:

Grantley Smith from UNSW WRL explains in this video:

Scrivener Dam model 2020 being tested at UNSW WRL, Sydney by Laura Montano, Ben Modra and Graham Knight (NCA)

The 2020 dam model is the third physical model of the dam constructed since its inception in the 1960’s. The original 1960's model was constructed in Kingston and was used to design the Lake and dam. The second model was constructed in 2009 to better understand the discharge capacity of the flood gates.

The Original Scrivener Dam model being tested in Kingston, Canberra [transparency]
Richard Clough, National Library of Australia, nla.obj-143772577

The current 2020 project is the most comprehensive model constructed of the dam and will be used to determine the hydraulic pressures in the stilling basin immediately downstream during a range of flood events. In addition, the NCA also investigated the potential for erosion downstream as well as several other ancillary tests. Sensors were placed around the model to measure a range of parameters and the model was tested up to an equivalent of a 1 in 160,000 year flood event. The outcomes of the study will inform potential future capital works on the dam and the study is expected to be completed in late 2020.