Is yesterdays high stage modelling, still todays high stage rating?

Daniel Budge and Andrew (Ted) Cutler - NSW Office of Water , 30 October, 2014

This report documents the process used to confirm a modelled high stage rating for the Namoi River at Mollee. It involved reviewing a flood mitigation study done in 1980 and comparing it to known gauging’s throughout the life of the station and the extrapolation gained through theoretical analysis.

The Mollee gauging station is a significant monitoring point in the Namoi catchment as it is approximately half way through the catchment. This gauging station indicates what type of flood impacts water will have on the remaining Namoi River townships and river sections of Wee Waa to Walgett after going through Narrabri and then downstream further from Walgett to Bourke on the Barwon Darling system.

The results confirm the findings of the flood mitigation study completed in 1980 and through theoretical analysis modern day gauging’s appear to fit with extrapolated high stage rating.

This study showed that through various means, previous modelled high stage ratings can be validated through the combination of actual measurements at a site and theoretical analysis.