The Challenge

Toowoomba Regional Council has undertaken extensive flood modelling of the Toowoomba catchments to better prepare for extreme rainfall events such as those experienced in January 2011. The Toowoomba CBD catchment consists of two main creeks, East and West, which merge to form Gowrie Creek just north of the CBD. Both catchments are small and steep creating a potential for flash flooding with minimal warning time. In 2013/2014, state-of-the-art water level gauges were installed at five locations throughout the Toowoomba creek (East, West and Gowrie) catchments with locations based on a combination of flood modelling and public input. A review of the gauge data was undertaken to determine the appropriateness of the gauge location in terms of providing early warnings of potential flooding to Toowoomba CBD and whether the gauge survey data was accurate.

Approach and Outcomes

The approach was to review the data history from each of Toowoomba Regional Councils (TRC) gauges. Reviewing the data quality also encompassed maintenance and data presentation systems. The analysis of Toowoomba CBD flood gauge data has revealed that the majority of existing flood gauges have been installed at appropriate locations and the review confirmed that Toowoomba CBD is prone to flash floods. The small catchment sizes and dependence on the rainfall in their immediate vicinity, results in some gauges recording peak depths independently of upstream events and gauges. Additional low-cost pluviographs have been recommended to improve TRC’s understanding of rainfall variation across catchments.