The review, conducted by specialist hydrologists and hydraulic engineers, Venant Solutions found the flood frequency analysis (FFA) process followed best practice.
The reports author presented the findings to Federation Council’s September meeting on Tuesday this week.
Venant Solutions confirmed that Mulwala flood estimates were sound, while suggesting higher flood levels could occur at Corowa and Howlong.
The review recommended further testing and clearer documentation, particularly around the Yarrawonga Weir gates and assumptions around historic events.
It also highlighted some concerns at Doctors Point and Corowa, where the method used may have underestimated peak flood flows.
The report examined the TUFLOW hydraulic model, which it described as well set up and appropriate for representing Murray River flood levels, including the operation of the Yarrawonga Weir gates.
Further testing and documentation was recommended to justify not extending the annual maximum flow series before the construction of the Hume Dam at Doctors Point and Corowa or vice versa at Yarrawonga; and for using the 1975 event as the historic event censoring flow at Doctors Point and Corowa, as opposed to the 1917 event used at Yarrawonga.
The report noted that hydraulic modelling assumed there were no outflows from Lake Mulwala into the Mulwala Canal and the Yarrawonga main channel and recommended that confirmation be sought that this assumption was consistent with current practice.
Read more in next week’s edition of the Yarrawonga Chronicle.
