Globally, more and more people are living in towns and cities, however, there are significant environmental challenges associated with urbanisation. For example, more intense rainfall predicted in Northern Europe will likely result in an increase in urban flood risk and reduced soil and water quality.
Nature-based solutions (NbS) are methods using or inspired by nature that benefit people and the environment. In this example, we looked at urban trees and the soil that they’re planted in, as a way to lessen urban flood risk by increasing the infiltration rate.
Understanding the infiltration status of urban soils can provide useful information on how a neighbourhood might deal with heavy rain and flooding. However, it is hard to identify areas with higher or lower flood vulnerability or implement the most appropriate land management practice, as conditions vary significantly, even within the same urban area.
Citizen science offers an opportunity to help fill this gap. In this two-year study lead by Earthwatch Europe, 520 citizen scientists assessed soil characteristics from under the same tree species (Linden trees, Tilia spp.) in three urban parks in London, Birmingham and Chantilly, France. Citizen scientists assessed an array of soil characteristics (soil colour, compaction, texture, moisture content and infiltration rate) as well as collected soil samples for lab analyses.
The data revealed that citizen scientists could perform simple measurements to be able to categorize whether an urban green space containing trees had high or low infiltration rate. These measurements indicate the capacity for water to soak away during a heavy rain event.
Using this information, we designed a flow diagram that could guide citizen scientists through the soil sampling process, with the output suggesting whether the sample location has a high or low infiltration rate, in turn indicating the flood mitigation capacity of that site. If the infiltration rate were to be classified as low and therefore potential flood risk high, the diagram suggests some simple actions that could be implemented to improve the soil.
Citizen science offers a robust and time efficient means for scientists to gather urban soil data over a large area. As well as this, the involvement of citizen scientists provides opportunity for learning and awareness, empowering local communities to understand and act to improve the soil conditions of their own local green spaces for flood protection.
Read the full paper:
Cárdenas, M. L., Buytaert, W., Loiselle, S., Narraway, C. L., Paul, J. D., and Pudifoot, B. (2021). When It Rains, It Pours: Integrating Citizen Science Methods to Understand Resilience of Urban Green Spaces. Frontiers in Water.