A screening method for urban drainage zones

Due to climate change, the storms have intensified leaving the urban drainage system and wastewater treatment plants hard to tackle with the large water quantities. In this study we develop a data-based screening method to identify which drainage zones would benefit most of blue-green infrastructure to avoid spilling of uncleaned water. First the precipitation and drainage zone flow rate data are pre-processed and de-seasonalized to remove the flow rate due to consumer wastewater. Then, system identification is applied for the rain periods and transfer function parameters for first order plus time delay model are collected. The screening index is calculated from the transfer function model parameters. The results show that the system is very nonlinear, but the mean values for the screening index is statistically significantly different for the drainage zones included to this study. The screening index clearly separates the different types of drainage zones and gives a reasonable suggestion for which drainage zones should be considered further for implementation of blue-green infrastructure like nature-based solutions