Case study

Mackenzie River Flood Study

ProjectMackenzie River Flood Study
ClientWesfarmers Curragh Pty Ltd and Jellinbah Resources Pty Ltd
LocationBlackwater, Queensland
Completion2013
Disciplines/ServiceHydrologic Model Analysis and Calibration
Hydraulic Model Development and Verification
WRM ContactMichael Batchelor

The Challenge

A proposed expansion of the Curragh North Coal Mine required a detailed flood study to determine design flood levels and required levee crest levels to protect the mine from flooding, as well as an assessment of the potential impacts of the levee on flood behaviour. The Mackenzie River catchment upstream of the mine has a total area of 50,000 and includes the Fairbairn Dam, which was constructed in the early 1970s. Recent major flood events provided significant quantities of high quality data, including flood extents and levels, as well as detailed stream gaugings taken at high flow rates. However, the rainfall data network is sparse in certain areas of the catchment.

A comprehensive flood study and impact assessment of the Mackenzie River in the vicinity of Wesfarmers’ Curragh mine was undertaken to support the design of levee protection works.

Approach and Key Activities

A large amount of historical data of varying quality needed to be collated and reviewed. Detailed assessment of rating curves at key stations was undertaken, including reconciling TUFLOW hydraulic model results with recorded data. A suite of 4 linked URBS models was developed for the major tributary catchments and calibrated to recorded data at approximately 20 stream gauges. Estimated design discharges from the URBS model were reconciled against flood frequency analysis results with and without the influence of Fairbairn Dam. The URBS model was used to estimate 1,000 Year ARI and PMF discharges. A TUFLOW hydraulic model of a 60 km reach of the Mackenzie River was developed for the estimation of flood levels and velocities and to assess the impacts of the proposed levee.

Outcomes

The project delivered a set of well calibrated and validated URBS hydrologic models for the Mackenzie River catchment, including separate models for the major sub-catchments of Theresa Creek, Nogoa River and the Comet River. The results of the modelling studies provided robust estimates of design flood discharges and levels which were used in detailed design of the proposed levee. Due to the significant risks and high value of infrastructure protected by the levee, the client appointed an independent consultant to provide ongoing peer review of the study methodology and results. This further increased the level of confidence in the study results.