Thabeban master drainage strategy - a wholistic approach to reducing flooding and increasing development yield in flat terrain by NIcole Bichel

Abstract

Drainage in existing urban areas can be complex, which is further impeded by excessively flat terrain. The suburb of Thabeban is no exception with many customer complaints regularly received by Council. These complaints relate to frequent and prolonged below floor level flooding of numerous residential and commercial properties. Furthermore, there is a large portion of undeveloped land (currently zoned as ‘residential’) which is lacking the required trunk drainage infrastructure to allow further development to occur. This study undertaken by SLR Consulting demonstrates the first principals’ approach of understanding the source and cause of the problem and how the whole system works to develop a tailored and wholistic drainage solution which not only maximised existing infrastructure but also provide confidence in allowing the development yields to be maximised. All elements of the solution were cognisant of: • The standard of service which would be required for existing property owners and expected for any new development; • the current community concerns; • the cost of construction and maintenance over the life of the drainage assets; and • an understanding of the risk associated with asset failure and/or storm events larger than the design event. For further understanding of how the drainage system operated, an innovative approach using water balance modelling was adopted to further assess the performance of the large existing retention basin. The model was used to represent the long-term water levels in the basins based on catchment inflows, soil and evaporation losses and any pumping regimes proposed. This study demonstrated how a thorough and detailed understanding of the system resulted in a drainage solution which maximised current infrastructure, was effective in reducing nuisance flooding, and presented sufficient understanding of the system behaviour to provide confidence in increasing development in a difficult catchment.