Application of the Monte Carlo Simulation Technique and URBS Model to the Coomera River Catchment for Design Flood Estimation

The currently recommended rainfall-based flood estimation method in Australia known as the Design Event Approach has limited flexibility in dealing with the probability aspects of various inputs to the runoff routing model. An advanced approach such as the Joint Probability Approach could overcome the limitations of the Design Event Approach, and as such, has been applied to the Coomera River catchment in the Gold Coast region using URBS model. It has been found that the URBS-Monte Carlo Simulation Technique (UMCST) provides a robust method for estimating a range of inflows to hydraulic/floodplain models to assess the impact of '100 year' storms on the Coomera floodplain. Further it is found that the UMCST technique provides similar design peak flow rates to the Design Event Approach using the temporal patterns derived specifically for the Gold Coast region.