Melbourne Water and DELWP commissioned a study to determine whether there was systematic bias in design flood estimates for Victorian catchments using the ARR2019 techniques and data sets.
The outcome of this assessment indicated that the use of the standard ARR2019 design inputs for Victoria is likely to result in an underestimate of design flood peak flow in the majority of catchments.
Preliminary investigations were trialled using three approaches to correct the bias observed in the design flood estimates for Victorian catchments. On the basis of these investigations, it was recommended flood estimates obtained using ARR2019 Data Hub regional information should be derived using the 75th percentile pre-burst rainfall (in lieu of the median value) in combination with unmodified Data Hub values of initial and continuing loss. Given the distribution of catchments considered, this recommendation is only supported by information obtained for catchments within loss region 3.