Abstract
Rapid urban densification coupled with climate-induced precipitation anomalies poses critical stormwater management challenges in temperate coastal environments. Nature-based solutions (NBS), notably extensive green roofs and permeable pavements, offer decentralized stormwater mitigation potential; however, their integrated hydrologic and pollutant attenuation efficiencies under coastal maritime climatic conditions remain incompletely quantified. This empirical study evaluated the performance of co-located extensive green roofs (100 mm substrate depth) and interlocking concrete permeable pavements against conventional asphalt and bituminous roof controls across a maritime temperate coastal urban catchment over an 18-month monitoring campaign (74 precipitation events). Hydrologic monitoring revealed that permeable pavements and green roofs achieved cumulative stormwater volume reductions of 78.4% and 57.2%, respectively, with permeable pavements exhibiting superior peak flow attenuation (mean lag time extension of 38 minutes). Water quality analyses indicated substantial interception of total suspended solids (>85% for permeable pavements, >72% for green roofs) and total zinc and copper (>70% reduction across both systems). Conversely, the extensive green roof exhibited net orthophosphate export during initial operational phases (+14.2% mass export), driven by organic matter leaching from the engineered growing media, before stabilizing. Permeable pavements exhibited steady effluent concentrations despite cumulative exposure to marine atmospheric aerosols and urban traffic detritus. These findings illustrate that while permeable pavements maximize volumetric attenuation and particulate entrapment in coastal settings, green roof media formulations require careful nutrient-balance optimization to mitigate adverse downstream nutrient enrichment, thereby providing critical design criteria for climate-resilient coastal urban watersheds.
