The Challenge

Toowoomba Regional Council comprises an area of nearly 13,000 km2 with a population of approximately 172,000 people more than 30 towns. In 2009 TRC commenced the Toowoomba Regional Planning Project to develop one integrated planning scheme policy covering the entire Council area. As part of this project, an assessment of the flood behaviour and flood risk in several towns in the region was required.
The objective of this project was to build a 1D/2D coupled MIKE FLOOD Flexible Mesh model to define the nature and extent of flood behaviour in the Upper Condamine River catchment and enable TRC to target future studies/investigations and inform the risk assessment, subsequent investigation of policy options and future Planning Scheme amendments.

Approach and Outcomes

The hydraulic modelling of the Upper Condamine River catchment was undertaken using a coupled 1D/2D MIKE FLOOD Flexible Mesh model. The model covered an area of approximately 2,230 km2 with mesh elements ranging from 3 m2 to 3,600 m2 in area. Over 30 bridges and culverts were represented in a 1D MIKE 11 model and coupled to the mesh topography. The model was validated to the December 2010 flood event. Comprehensive mapping showing modelled surface elevations, velocities, depths, flood hazard and hydraulic categories for the full set of modelled events was also produced to inform future Planning Scheme amendments.