Sponge city concept in stormwater management and its applicability to Finland

Abstract

Cities around the world are experiencing increasing urban floods. A key issue in rapidly expanding urban environments is that ground surfaces are covered by impermeable materials that prevent natural water infiltration. Conventional drainage systems were designed to address this challenge, but they are increasingly unsuccessful at managing stormwater quality and quantity in worsening climate conditions.

The aim of this study was to examine what the sponge city concept (SCC) entails in urban development, to compare it with similar stormwater management approaches, and to assess whether it can be applied to Finland. The study presents the current state of stormwater management in Finland and discusses the potential benefits and challenges associated with the use of SCC. The study was conducted as a literature review.

SCC’s premise is to resemble the natural water cycle and to place sustainable stormwater management at the core of urban planning. The principle of SCC is to prevent flooding caused by heavy rainfall by retaining, storing, and reusing water. Its key techniques include increasing the use of permeable pavements, green roofs, parks and other nature-based solutions integrated with engineered solutions. Together, these form a system capable of retaining large volumes of water.

Although Finland does not officially use the sponge city concept, Finnish stormwater management practices include similar features. This study explores how these ideas are already applied in Finland and whether the concept could be adapted further to fit Finnish conditions. Finland’s climate differs significantly from the temperate conditions for which SCC was developed.

The main conclusions are that SCC is an effective solution for increasing urban resilience, as its impacts extend beyond stormwater management. The concept helps to restore elements of the natural hydrological cycle in urban areas and reduces peak runoff. SCC could advance Finnish cities as a strategic long-term design-basis for climate resilience since it urges cities to bring stormwater management to a regional plan scale. The findings suggest that there is no clear cause to avoid implementing sponge city practices even when the Finnish winter inflicts seasonal variation in effectiveness.