Evaluating Sponge City volume capture ratio at the catchment scale using SWMM

Area of Science:

• Urban Hydrology
• Environmental Engineering
• Sustainable Urban Development

Background:

• China's Sponge City initiative mandates extensive Low Impact Development (LID) stormwater infrastructure.
• Ambitious precipitation capture targets (80-85%) are set for Sponge Cities.
• Limited research exists on achieving these goals within existing urban constraints.

Purpose of the Study:

• To evaluate the feasibility of Sponge City rainfall capture goals at the catchment scale using hydrologic modeling.
• To assess the long-term potential of LID implementation in Beijing.
• To provide a decision-making basis for urban planning.

Main Methods:

• Utilized long-term continuous hydrologic modeling with the Stormwater Management Model (SWMM).
• Employed detailed land cover classification from satellite imagery for model parameterization.
• Generated synthetic high-resolution rainfall time series from historical data for a 35-year simulation period.

Main Results:

• A calibrated SWMM model for a 133 km² urban area showed good agreement with observed runoff.
• Simulations indicated that converting 30% of roofs to green roofs, 10% of green areas to rain gardens, and 35% of paved areas to permeable pavement increased annual rainfall capture from 59.9% to 82.2%.
• These realistic LID implementation levels are sufficient to meet Sponge City goals.

Conclusions:

• Sponge City rainfall capture targets are achievable in Beijing's urban landscape with strategic LID implementation.
• The study validates the effectiveness of specific LID strategies for stormwater management.
• Findings support informed planning for sustainable urban water management.