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Document Overview
This is a peer-reviewed research article published by MDPI in 2020 in the journal Sustainability, with Andreas Matzinger listed as the author in the document metadata. Its subject is the spatial compatibility of nature-based solutions (NBS) for reducing urban heat island (UHI) effects and stormwater pollution at the same location, using Berlin as the case study.
Context and Motivation
- The article notes that 55% of the world's population lives in cities and that urbanization and climate change intensify urban challenges.
- NBS are presented as options that can serve several purposes at once, including stormwater retention, reduced surface water pollution, UHI mitigation and air pollution reduction.
- Berlin identified UHI reduction as a major focus of its climate adaptation programme, and surface water pollution during storm events as a major focus of its EU Water Framework Directive implementation plan.
Methodology
- The analysis covered about 14,000 building block and street segments in Berlin.
- UHI data came from a city climate analysis map based on the FITNAH model, classified into four categories following VDI directive 3787 Part 1.
- Stormwater pollution loads (in g/ha/yr) were derived from a monitoring programme across five catchments combined with the ABIMO 3.2 water balance model, for four parameters: PAH, TSS, zinc and Terbutryn.
- High pollution was defined using a mean90% threshold, and a block was classed as high-pollution if at least one parameter exceeded it. The authors state that the sample size of four UHI categories was very small, so correlation results indicate a tendency only.
Key Findings
- Medians of pollution loads and UHI were positively correlated for all four parameters, with Spearman coefficients of 1 for TSS and PAH and 0.8 for Terbutryn and zinc.
- Out of the areas analysed, 2270 showed both high pollution load and high UHI, while 7911 had low pollution and low UHI.
- Approximately 93% of high-UHI areas also had high stormwater pollution, and almost 38% of high-pollution areas had high UHI.
- In 1757 of the 2270 matching areas, at least three parameters had high pollution loads.
Strategy and Settlement Structure
- Under a strategy to mitigate both challenges at all sites, the article finds high compatibility in Berlin. Under a strategy that prioritises low-pollution sites in combined sewer areas, compatible areas fall to 600.
- Matching areas are mainly in densely built districts; densely built living and mixed-use areas account for 78% (1778) of matching areas.
NBS Suitability
- The article cites the KURAS project in naming infiltration/rain gardens, ponds, rainwater harvesting and vegetated retention soil filters as suitable for both aims.
- It notes that pollutants can be diverted to the local environment, and suggests combining technical stormwater treatment with NBS such as green roofs.
Why It Matters for Urban Planning of Smart Cities
The authors state that the approach can be used for strategic planning of targeted NBS implementation, identifying where urban challenges coincide so decision makers can prioritise investment. They suggest it could be transferred to other cities with temperate climates and extended to further challenges such as biodiversity or flood prevention.