Urbanization creates problems for the natural water systems, such as an increase in run- off volume due to the impervious surfaces and a negative impact on groundwater recharge. These changes and exposure to contaminants such as suspended/dissolved solids and heavy metals severely degrade stormwater quality. In Christchurch, heavy metals such as zinc found in run-off, which is mainly sourced from galvanized roofing. The main idea of this research is to solve run-off issues at the source, along with the construction phase. This idea is aligned with the NZ's Unitary Plan to keep rainwater run-off after a new development equal or less than the run-off that occurred before the development. Different methods of treatment for roof run-off were evaluated in this research to propose a sustainable solution followed by an assessment. A multi-layered planter box raingarden was selected since it helps to landscape, improve water quality, and perform as an attenuation device. The research concentrated on maximizing water quality while maintaining a required flowrate. The planter box raingarden performed at a low vertical hydraulic conductivity rate of 164 mm/hr and achieved a high removal rate for heavy metals. The removal rate for dissolved zinc and total zinc was 99.7% and 99.1%, respectively. The results explained that the planter box raingarden performs well as an attenuation device while adsorb and filter contaminants remarkably.
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