Figure 32. Overtopping and piping failure configurations (US Army Corps of engineers, 2014)
The hydraulic modelling was undertaken using the TUFLOW software package. TUFLOW software can
dynamically simulate linked one-dimensional (1D) and two dimensional (2D) hydraulic models and has
the capacity to represent complex changes in topography, hydraulic structure, boundary conditions,
land use classification, floodplain storage and floodplain/channel interaction. Resulting flood inundation
results maps are provided in Appendix D.
The results of the simulation testing indicated that the OCP is the primary receptor of breach outflows
in all scenarios with these being heavily attenuated and controlled by its spillway discharge. The
relatively smaller outflow volume discharge for Stage 1 Scenario was conveyed through the site
drainage system and release to Dee River, completely contained within the natural channel banks as
depicted in Figure 33. For the Stage 2 Scenario a dam break would primarily impact the site
infrastructure immediately downstream of the OCP. The outflow discharge exceeds the spillway
capacity and overflows are expected to impact the Process Plant and ROM pad. The maximum depths
and velocities were observed immediately downstream of the OCP and natural flow paths towards Dee
River resulted in the highest hazard risk classification to be concentrated in these areas, as depicted in
Figure 34.
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Wulguru Technical Services Pty Ltd – Supporting Information to Amend an Environmental Authority
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