A 4-Year Field Experiment on an Urban Permeable Sidewalk on Its Runoff and Surface Temperature Performance

Permeable pavement is commonly used for urban stormwater management and urban heat island mitigation. It has been proven that permeable pavement has such benefits; however, the clogged permeable pavement could lose its function, and there are relatively few studies on its long-term monitoring. This study monitored an in-use permeable sidewalk in central Taipei City, Taiwan, and presented its four-year performance. In the study area, the permeable sidewalk occupies nearly half of the drainage area. The onsite data showed that the average runoff reduction rate in the first year (2021) was 41.2% but decreased to 28.8% in the fourth year (2024). The differences in runoff reduction rate between different rainfall patterns are also discussed. If the permeable pavement is not cleaned, it might lose its permeability after 7 years. The results of the surface temperature monitoring show that the average surface temperature of permeable pavement is maintained at 28.8 °C over the four-year period, whereas the surface temperature of impermeable pavement increases annually. This finding verified that permeable pavement is helpful in stabilizing surface temperatures in urban areas, thereby combating the warming environment. In addition, Wet Bulb Globe Temperature (WBGT) was tested in this study. The results of WBGT showed that the WBGT above the permeable pavement is lower than that on impermeable pavements by about 1–2 °C from 12 p.m. to 16 p.m. This implies that permeable pavement may contribute to a comfortable thermal environment for the public. The results of this study provide crucial information for maintaining permeable pavement and enhancing its beneficial functions.