City or paddling pool? – emergency solutions for future floods

Floods, droughts and extreme weather events will be increasingly prevalent in the future. In many urban areas there are few permeable and green surfaces, resulting in pooling water and significant flood damage following storm events. This rain and melt water is commonly referred to as stormwater by urban planners. 

The ISMO project seeks solutions to urban flooding and varying conditions through the implementation of natural stormwater management. Natural stormwater management has many benefits: urban nature becomes enriched, the amount of stormwater decreases and the nutrient load that ends up in water bodies decreases. But what interventions and policies can be implemented to bring about these benefits?

Parks and green spaces

ISMO project supports a variety of nature-based solutions to stormwater management, including establishing parks and green spaces in strategic locations. While many residents consider these spaces to be solely for leisure and exercise, they are also powerful resources in holding and diverting potentially damaging stormwater. 

Green spaces act like sponges during rain and melt events, by absorbing a lot of water. This function can help to prevent, or at least mitigate, the accumulation of water on roads and in built-up areas. It is worth noting that the maintenance costs for parks are relatively low, especially when compared to the costs of repairing flood damage to built-up areas. 

Green roofs in stormwater management

These days, green roofs are strongly encouraged in plans for new urban and built-up areas. These roofs are commonly lauded for their biodiversity and carbon sequestration potential; however, they also play a significant role in stormwater management. Green roof-style solutions in densely built-up urban areas will become increasingly valuable as climate change brings more frequent and severe storm events to northern and western Europe. 

Much like parks and other green spaces, these roofs absorb and slow down the flow of stormwater, thus preventing this water from pooling on impermeable surfaces. Green roofs can commonly be installed on flat or near-flat roofs, so long as appropriate maintenance procedures are followed. 

Utilizing stormwater wetlands in stormwater management

Wetlands offer multiple ecosystem services to nearby communities. Stormwater wetlands can be created by establishing vegetated, or partially vegetated, areas which are either permanently or temporarily covered with water. These patches of wetland are effective at slowing and detaining stormwater and reducing flooding impacts. 

 Other benefits of these created habitats include reducing the urban heat island effect and improving urban biodiversity. Urban wetlands also improve surrounding water quality, as the contaminants in stormwater settle to the bottom of the watercourse. The vegetation in and around these wetlands also binds nutrients and impurities, as well as sequestering carbon and improving air quality. Due to their water-purifying qualities, stormwater wetlands are commonly built close to water bodies to purify local catchments. 

Climate change will lead to northern and western European countries experiencing more frequent and more severe storm events. Stormwater management must respond by becoming more sustainable and efficient. ISMO is a timely project that will make an important contribution, by providing modelling and simulation tools for stormwater management, as well as monitoring data for a variety of nature-based solutions. The next generation of stormwater professionals will make flood management more sustainable and more beneficial for local communities. 

Original text: Emilia Suutari, Niklas Turva, Roope Haapala, Saana Taponen, Sebastian Lindblom 
Translated: Senior Advisor Joseph Perry
Published (in Finnish) in Talk by Students 5/2023

Sources: Turku UAS, Vevira, LUVY, Ympäristö, Pien-Saimaa, leca