<p>Rapid urbanization reshapes landscape patterns and intensifies stormwater runoff pressure, yet the shifting cost-effectiveness of green infrastructure across different urban development phases remains poorly quantified. Focusing on Beijing’s 150 km<sup>2</sup> urban subcenter, this study quantified 21 block-level landscape metrics, which were distilled via principal component analysis into five landform indicators: dominance, fragmentation, edge, aggregation, and shape. K-means clustering classified each block into constructed, constructing, or unconstructed phases. A life-cycle cost analysis then estimated the bioretention investment required to meet an 80%–85% annual runoff volume control target. The constructing phase, characterized by contiguous impervious surfaces at the urban edge, demands 45% more bioretention investment per unit area than the unconstructed phase and 4% more than the constructed phase. As land transitions from unconstructed to constructed, bioretention costs increase by approximately 109% for agricultural land and 86% for green space, whereas changes for residential and commercial areas remain minimal. These results indicate that uniform runoff control investment policies risk underfunding rapidly developing fringes and overfunding consolidated urban centers. A phase-specific and land use–sensitive investment strategy is therefore necessary to avoid capital inefficiency while achieving runoff control goals. By linking dynamic landscape evolution with infrastructure economics, this study provides a forward-looking tool to guide runoff control investment during urban expansion.</p>

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Differences in cost efficiency of runoff control in different urban built-up phases

  • Zijing Liu,
  • Haiyuan Yao,
  • Zhengxia Chen,
  • Gaoling Zhang,
  • Qi Liu,
  • Haifeng Jia

摘要

Rapid urbanization reshapes landscape patterns and intensifies stormwater runoff pressure, yet the shifting cost-effectiveness of green infrastructure across different urban development phases remains poorly quantified. Focusing on Beijing’s 150 km2 urban subcenter, this study quantified 21 block-level landscape metrics, which were distilled via principal component analysis into five landform indicators: dominance, fragmentation, edge, aggregation, and shape. K-means clustering classified each block into constructed, constructing, or unconstructed phases. A life-cycle cost analysis then estimated the bioretention investment required to meet an 80%–85% annual runoff volume control target. The constructing phase, characterized by contiguous impervious surfaces at the urban edge, demands 45% more bioretention investment per unit area than the unconstructed phase and 4% more than the constructed phase. As land transitions from unconstructed to constructed, bioretention costs increase by approximately 109% for agricultural land and 86% for green space, whereas changes for residential and commercial areas remain minimal. These results indicate that uniform runoff control investment policies risk underfunding rapidly developing fringes and overfunding consolidated urban centers. A phase-specific and land use–sensitive investment strategy is therefore necessary to avoid capital inefficiency while achieving runoff control goals. By linking dynamic landscape evolution with infrastructure economics, this study provides a forward-looking tool to guide runoff control investment during urban expansion.