The Potential of Stormwater Management in Addressing the Urban Heat Island Effect: An Economic Valuation

• Pankow is a residential neighbourhood in Berlin, Germany. 117 hectares with population density and age structure is representative of typical Berlin areas. 
• High building density creates UHI conditions. Average daytime UHI intensity 2.6°C above surrounding rural areas. 
• Demographics: 92.16% residents aged 0–74 years, 7.84% aged 75+ years (more vulnerable to heat stress).

To quantify UHI mitigation potential through heat-related morbidity and mortality reductions across three UGI scenarios, and assess economic feasibility using Cost-Benefit Analysis incorporating both private ecosystem services and social health benefits.

• Scenario B (most economically robust): lowest installation and O&M costs due to minimal facade greening. 
• Scenario C: highest costs due to extensive facade greening with highest annual maintenance. 
• All scenarios achieved positive net returns. Unit costs varied by measure: tree drains (highest installation, lowest O&M), facade greening (highest O&M), green roofs (moderate costs).

• Heat-related hospitalizations reduced by 0.94–2.66 cases annually across scenarios. 
• Annual heat-related deaths avoided: 0.46–0.78 cases. 
• Total UGI benefits over 50 years: EUR 56.8–125.1 million. 
• UHI mitigation benefits contributed 28–41% of total benefits. 
• Positive NPV and BCR > 1 for all scenarios confirming economic feasibility.

• Implementation of tree drains, facade greening and green roofs for stormwater retention and cooling. 
• Climate data analysis using 8m × 8m grid cells measuring UTCI heat stress at pedestrian level. 
• Economic valuation of damage costs avoided through reduced hospitalizations (€3,300 per case) and mortality (Value of Life Year approach).
• Dual discounting scheme (3% private, 2.1% social) applied over 50-year horizon.

KURAS project consortium
www.kuras-projekt.de

Pankow nature-based solutions

An urban neighborhood in the Pankow district of Berlin implemented three nature-based solution scenarios to address stormwater management while mitigating urban heat island (UHI) effects. The 117-hectare residential area, representing typical Berlin demographics with 23,276 inhabitants in 2017, combines multi-story apartments from the 1920s–1930s with post-war higher residential buildings.

The KURAS project ("Concepts for urban stormwater management and sewer systems") developed three independent UGI scenarios: 

• Scenario A (lowest greening coverage), 
• Scenario B (high tree drain coverage with low facade greening), and 
• Scenario C (highest overall greening including extensive facade greening and green roofs). 

Measures included tree drains, facade greening, green roofs, swales, ponds and permeable pavement.

Climate data analysis using UTCI (Universal Thermal Climate Index) measured daytime heat stress reductions. Tree drains achieved the strongest cooling effects with up to 711 hours annual heat stress reduction, while facade greening and green roofs reached maximum 381 hours per year. Strategic placement proved more important than sheer volume of green cover.

A 50-year Cost-Benefit Analysis used dual discounting: 3% for private costs/benefits and 2.1% for social benefits including health impacts. Benefits included reduced heat-related hospitalizations and mortality valuations alongside ecosystem services (stormwater run-off reduction, building longevity, habitat creation, aesthetic improvements, energy savings, pollution and CO₂ reduction).

All three scenarios showed positive Net Present Values with Benefit-Cost Ratios above 1. Scenario B performed best economically despite lower total benefits, due to substantially lower implementation and maintenance costs. Scenarios A and C achieved similar UHI mitigation benefits (€35.3 million and €34.7 million respectively) through different approaches: Scenario A through strategic placement, Scenario C through greater greening coverage (28.92% of site).

Monte Carlo sensitivity analysis with 10,000 iterations confirmed robust results: Scenario B showed 100% probability of economic feasibility, while Scenarios A and C showed 64% and 63% respectively.