Queensland Urban Utilities reviewed flow diversion weir, gate, and pump settings to minimize manhole flooding and Emergency Relief Structure (ERS) discharge in the Norman Creek catchment of Brisbane.

Changes to operational settings that reduce ERS discharge may cause manhole flooding to increase, so it was necessary to run a multi-objective optimization to determine operational settings that provide the best balance of each performance metric.

OptimizerTM (by Optimatics) was linked directly to InfoWorks ICM.  The detailed ICM model takes approximately three hours to run a 24-hour simulation.  To allow the optimization to evaluate thousands of control setting options, the model was trimmed by removing areas outside of the zone of influence affected by the alternatives to be considered.  WCS developed a unique model trimming tool for this process that automatically applied time series boundary conditions.  The trimmed model achieved precise hydraulic results for the study area and reduced the simulation time to under five minutes.

The optimization demonstrated that the existing control settings are near optimal if receiving water (river and creek) levels are ignored.  Once receiving water boundary conditions are included, the system performance changes and adjustment of control settings can significantly help to reduce manhole flooding without significantly increasing ERS discharge.