Millmerran Urban Stormwater Master Plan

Millmerran, located approximately 80 km south-west of Toowoomba, is subject to relatively frequent overland flooding. There are also a number of known drainage issues in the township. The primary focus of the Millmerran Urban Stormwater Master Plan (USMP) was on overland flow; short duration flooding of backyards, drainage paths, streets and rural properties caused by stormwater as it makes its way into the creek and river system. The aim of the project was also to investigate and address local stormwater quality conditions and future requirements relating to Water Sensitive Urban Design (WSUD).

The objectives of the USMP were to: 

• Provide an understanding of the existing catchment conditions;
• Assess the capacity of existing stormwater infrastructure;
• Identify drainage problem areas within the Millmerran town boundaries;
• Propose measures to improve infrastructure performance and mitigation of inundation and ponding of water within the streets following heavy storms; 
• Determine catchment management and WSUD measures that will enhance sustainability and protect the region’s environmental values; and
• Consider and address the challenges of implementing the strategy.

The USMP concentrated on mitigating existing drainage and overland flow problems with inclusion of new trunk drainage and cross-drainage for future development. Conceptual water quality (MUSIC) and water quantity (TUFLOW) models were developed to identify the existing drainage problems and water quality treatment devices required.

In consultation with Council, WMS identified the criteria and associated weightings to be applied in the assessment of potential management options. The criteria were developed based on Triple Bottom Line (TBL) principles and have been assessed and sized in accordance with the Desired Standards of Service (DSS) for cross-drainage. The developed USMP and concept layout of proposed drainage infrastructure provided Toowoomba Regional Council with a basis for design of future stormwater drainage works in Millmerran.