Sustainable stormwater management in Stockholm's inner city

Abstract: Much like other cities Stockholm has traditionally used a technical system for managing stormwater. With time this system has become overburdened and has led to large environmental concerns. To reach water quality goals set by the EU Stockholm needs to decrease pollution released to recipients by 70-80%.  Green infrastructure (GI) has increasingly been used as an alternative and addition to technical stormwater systems. Many studies have been conducted on different solutions and their stormwater management performance. The City of Stockholm have done research on numerous solutions to evaluate their performance in the context of Stockholm as well. However, implementation in the inner city is slow, thus this study explores why this is the case, and how Stockholm’s stormwater management goals can be reached. Stockholm predominately uses trees planted in plant beds using structural soil, and a combination of constructed wetlands and wet ponds for stormwater management. In new developments there is no real concern, as the GI can be included in planning at an early stage. Including these solutions in existing environments causes issues related to space, both above and below ground, and costs. Therefore, other solutions need to be found. This study explored green roofs, green walls and permeable pavements as possible options. Additionally, it found that finding new space that has previously not been used for GI could be an option. To mitigate financing issues new ways of promoting investment into GI from private property owners could be utilized, but that there also is a mismatch between supposed support for sustainable stormwater management on the political side and funds allocated. Finally, the study recommends that Stockholm takes the technical systems into account and explores what GI measures best work together with it to more effectively decrease pollution.