Assessing carbon emission impacts of sponge city development: insights from runoff reduction analysis

This study aimed to quantify the impact of sponge city facilities on both runoff reduction and carbon emission mitigation, providing valuable insights for sustainable urban development. Using the Storm Water Management Model (SWMM) 5.2 in conjunction with carbon emission factor calculations, we comparatively evaluated the annual runoff reduction and carbon emission abatement potential of traditional drainage systems versus those incorporating sponge city facilities. Our results showed that the implementation of sponge city facilities resulted in a substantial decrease in runoff volume (100,840 m³), and a corresponding reduction in carbon emissions (7,089.85 kg CO₂ eq) compared to the pre-renovation conditions. Additionally, this work assessed five sponge city facilities: green roofs, permeable pavements, sunken green spaces, rain gardens, and overflow storage ponds. Among these, overflow storage ponds demonstrated the highest efficiency in both runoff reduction (35,879 m³) and carbon emission mitigation (2,522.57 kg CO₂ eq). Rain gardens showed the second-best performance, while sunken green spaces had the least impact. Our study provides a novel technical framework for quantifying and evaluating carbon emissions in urban drainage systems. Our findings offer reliable data support for urban planners and policymakers, contributing to evidence-based decision-making in the design and implementation of sponge city projects.