The purpose of this report is to investigate water sensitive urban design (WSUD) and its application to industrial areas. Water sensitive design is a sustainable development tool, its aim is to minimise the number and degree of disruptions a development can have on natural water processes. A literature review of water sensitive design found only very limited information on the subject with regards to industrial areas.
The study focuses on Brisbane’s Gateway Ports Area (BGPA) an industrial area that is rapidly growing as a result of significant investments from the Queensland Government, Their aim is to transform the area into one of Australia’s largest global trade and industrial centres. To quantify the results and for modelling purposes TradeCoast Central located at centre of the BGPA was chosen as a case study site.
There are several properties of an industrial estate that distinguish it from a residential development. Issue for industrial developments in the BGPA include, contaminated soils and Acid Sulphate Soils (ASS), large infrastructure requirements, high water table, the conservation value of the area, and the different water requirements for an industrial estate. These issues limit the use of common control and treatment measures such as infiltration and filtration techniques, open retention ponds, wetlands and porous pavement. It became apparent from this analysis and evaluation of various control measures that the most effective way of implementing water sensitive design is though the control of runoff from roof catchments.
Two different roof catchment water sensitive design measures were investigated in detail, rainwater tanks and green roofs. To evaluate both measures, two daily water balance models were created that utilised historical rainfall and evaporation data. The balance was further tested against design storms created in XP RAFTS 2000.
The results of the modelling led to the conclusion that rainwater tanks could not effectively serve as a detention facility and still provide a reliable supply of water for non-potable uses. The rainwater tanks responded well to design storms where the initial tank was at its minimum and maximum space was available for retention. The results indicated that 150KL to 170KL tank would retain enough water to capture the peak of the 100-year design storms for a one-hectare roof. However the retention capabilities of the tank reduced significantly for the historical recorded data model when the initial water volume in the rainwater tank increased, thereby reducing the volume available for retention. This was of concern as statistical analysis of the rainfall data revealed the tank was frequently at 95% of its capacity. It was concluded that rainwater tanks could not effectively serve as both a retention facility and provide a reliable supply of rainwater.
Green roof systems were tested as an alternative solution for roof catchments. Green roofs are gardens constructed on the roof of a building. Green roofs have many proven benefits including detention and collection of rainwater; insulation for the building and some types may provide a recreational area. The reasoning behind the green roof is that vegetation, which can respond to changes in climate and water availability, can control the water removal process; these variable water removal rates are desirable and important given the erratic Australian climate.
Modelling of green roofs provides very interesting and promising results in terms of detention with between 50% and 90% of the runoff returned to the atmosphere via evapotranspiration. However, the lack of available data limits the ability of the model to fully test the assumptions behind the model and further information is required to verify the results. Horticultural information on evapotranspiration of water in thin soil layers is required, as well as an understanding of the effects of “roof climates” where plant exposure to wind and sunlight is increased. Field-testing should also be completed to analyse the movement of water in thin soil layers that overlay the impermeable boundary.
Though the report focuses on industrial sites and large roof areas, the results are applicable for lower scale residential allotments. The additional amenity space created by the green roofs could be of greater value in a residential area, particularly for units and townhouses.