Designing and Implementing Green Roofs for WSUD in Australasia: A Trans-Tasman collaboration

Green roofs offer many potential benefits to water sensitive cities. However, it is important to understand that green roofs are a highly engineered best management practice and the purpose and the design greatly affect their performance. There are three key factors to designing a green roof. These are as follows: 1. Plant selection. 2. The Soil (Substrate). 3. The Drainage. Stormwater360 is a specialist stormwater solutions' provider based in Australia and New Zealand. Over the last 3 years Stormwater360 has been developing a pre-vegetated modular hybrid green roof system for use in Australasia. In March of 2012 Stormwater360 installed New Zealand's largest extensive green roof at Mount Difficulty wines in central Otago. The roof was designed to have many functions including the following: 1. Stormwater Reduction. 2. Disposal of process water. 3. Insulation. 4. Energy reduction. 5. Aesthetically pleasing. A section of this roof has been established at the University of Canterbury in Christchurch. This has allowed detailed and controlled monitoring of the system for its effect on water quantity and quality. This study has examined the effect of soil depth and various plant species and has monitored the performance over 18 months through various climatic conditions. Stormwater360 has used these results of the Canterbury Study to develop a Stormwater360 green roof node for MUSIC (Model for Urban Stormwater Improvement Conceptualisation). The node allows the conceptualisation of the potential benefits and applications of green roofs in water sensitive site design. The paper will discuss the development of the system, results of the monitoring and how these results were used to develop the MUSIC node. The paper will also give some examples (case studies) of different green roof designs installed over the last 3 years.