Search Results (84)

Permeable pavement is an alternative to conventional impermeable pavement for various applications. However, a common issue with permeable pavement is clogging over time. Permeability is a parameter that reflects the capacity of the pavement to reduce surface runoff; a decline in permeability implies the occurrence of clogging. In this study, permeability data collected on pervious concrete (PC) and JW Eco-Technology (JW) revealed that JW maintained consistent permeability over time. However, PC displayed reduced values, and several locations along the edges had zero permeability, despite no regular vehicular and pedestrian use. Therefore, a portable pressure washer was used to clean the pavements. The cleaning procedure was able to recover the permeability of the areas that showed signs of clogging (0 to 2.69 cm/s) and restore the permeability of PC up to 4.60–5.58 cm/s for corner and center areas, respectively. Moreover, visual inspection using a borescope further revealed the full function of the JW pores (aqueducts), regardless of cleaning. Regardless, it is recommended that periodic cleaning maintenance be performed for both PC and JW using a pressure washer due to its convenience and efficacy, which will be discussed. Full article

The U.S. Environmental Protection Agency (EPA) developed the concept of Water Quality Volume (WQv) as a Best Management Practice (BMP) to treat the first 25.4 mm of rainfall in urban areas, aiming to capture approximately 90% of annual runoff. However, applying this urban-based standard—designed for areas with over 50% imperviousness—to rural regions with higher infiltration and pervious surfaces may result in overestimated facility capacities. In Korea, a uniform WQv criterion of 5 mm is applied nationwide, regardless of land use or hydrological conditions. This study examines the suitability of this 5 mm standard in rural catchments using the Hydrological Simulation Program–Fortran (HSPF). Eight sub-watersheds in the target area were simulated under varying cumulative runoff depths (1–10 mm) to assess pollutant loads and runoff characteristics. First-flush effects were most evident below 5 mm, with variation depending on land cover. Nature-based treatment systems for constructed wetlands were modeled for each sub-watershed, and their effectiveness was evaluated using Flow Duration Curves (FDCs) and Load Duration Curves (LDCs). The findings suggest that the uniform 5 mm WQv criterion may result in overdesign in rural watersheds and highlight the need for region-specific standards that consider local land-use and hydrological variability. Full article

Urbanization has profoundly transformed land surface morphology and amplified thermal environmental modifications, culminating in intensified urban heat island (UHI) phenomena. Local climate zones (LCZs) provide a robust methodological framework for quantifying thermal heterogeneity and dynamics at local scales. Our study investigated the Changsha–Zhuzhou–Xiangtan urban agglomeration (CZXA) as a case study and systematically examined spatiotemporal patterns of LCZs and land surface temperature (LST) from 2002 to 2019, while elucidating mechanisms influencing urban thermal environments and proposing optimized cooling strategies. Key findings demonstrated that through multi-source remote sensing data integration, long-term LCZ classification was achieved with 1,592 training samples, maintaining an overall accuracy exceeding 70%. Landscape pattern analysis revealed that increased fragmentation, configurational complexity, and diversity indices coupled with diminished spatial connectivity significantly elevate LST. Rapid development of the city in the vertical direction also led to an increase in LST. Among seven urban morphological parameters, impervious surface fraction (ISF) and pervious surface fraction (PSF) demonstrated the strongest correlations with LST, showing Pearson coefficients of 0.82 and −0.82, respectively. Pearson coefficients of mean building height (BH), building surface fraction (BSF), and mean street width (SW) also reached 0.50, 0.55, and 0.66. Redundancy analysis (RDA) results revealed that the connectivity and fragmentation degree of LCZ_8 (COHESION8) was the most critical parameter affecting urban thermal environment, explaining 58.5% of LST. Based on these findings and materiality assessment, the regional cooling model of “cooling resistance surface–cooling source–cooling corridor–cooling node” of CZXA was constructed. In the future, particular attention should be paid to the shape and distribution of buildings, especially large, openly arranged buildings with one to three stories, as well as to controlling building height and density. Moreover, tailored protection strategies should be formulated and implemented for cooling sources, corridors, and nodes based on their hierarchical significance within urban thermal regulation systems. These research outcomes offer a robust scientific foundation for evidence-based decision-making in mitigating UHI effects and promoting sustainable urban ecosystem development across urban agglomerations. Full article

To address the mechanical deficiencies of traditional pervious concrete and promote its practical implementation, this study developed a high-performance pervious concrete model using conventional materials and methods, achieving a permeability coefficient of 4.5 mm/s with compressive and flexural strengths exceeding 45 MPa and 5 MPa, respectively. Central composite design (CCD) response surface methodology was employed to investigate the individual and synergistic effects of the water–cement ratio (W/C), nano-silica (NS), and carbon fibers (CF) on permeability, compressive strength, and flexural strength. Statistical models demonstrating prediction errors within 7% of experimental values were established, supplemented by a microstructural analysis of the concrete specimens. The results demonstrated that (1) the W/C ratio significantly influences overall performance; (2) NS enhances mechanical strength while reducing permeability, though excessive NS content induces weak interfacial zones that compromise strength; (3) CFs exhibit negligible impact on compressive strength but substantially improve flexural performance; and (4) significant synergistic interactions are present across W/C ratio, NS, and CFs concerning flexural strength parameters, while no significant interaction was observed for compressive strength. Full article

Environmental impacts, such as elevated temperatures due to urban heat islands (UHIs), associated with land cover change due to urbanization, should not be ignored. In contrast to conventional impermeable concrete, permeable pavements have been implemented as green infrastructure strategies for achieving environmental benefits, such as stormwater management. Their impacts and benefits on other environmental aspects should not be ignored, especially for those with limited discussion in the literature. Therefore, this study monitored the surface and air temperatures of three types of pavements: conventional impermeable concrete (IC), pervious concrete (PC), and the patented JW Eco-technology (JW). As UHIs are more intense in the summer, temperature profiles during targeted periods when surface temperatures exceeded 40 °C for consecutive days were examined. In addition, as an available option at the study site, shade was created to evaluate its effect on surface temperatures across the pavement systems. Overall, the annual average surface and air temperatures of the three pavements were similar. However, seasonal and diurnal variations in temperatures were both observed, suggesting summer was the season when the differences in temperatures among pavements were most noticeable. Investigation during the targeted periods revealed that the average surface temperatures of PC were 2.4–2.7 °C and 3.2–3.3 °C higher than those observed on IC and JW, and the average air temperature of PC was 1.8 °C greater than that of IC and JW between 12:00 and 16:00. On the contrary, the average surface temperatures of PC were significantly lower than those on IC (1.3–1.4 °C) and JW (1.5 °C) between 21:00 and 5:00. Results also indicate that shade was an effective way to alleviate the high surface temperatures during the warm hours by lowering surface temperatures 21.0 °C, 15.4 °C, and 15.0 °C, for PC, IC, and JW, respectively. Finally, temperatures associated with the aqueducts of JW Eco-technology and the impacts on overall surface temperatures will be discussed. Full article

Internal drainage is crucial for preventing water damage in pavement structures. Pervious concrete is widely used in road projects due to its excellent drainage capacity, scour resistance, and durability. This study optimizes the mix design of pervious concrete by considering gradation (three levels), water-cement ratio (0.3, 0.35, 0.4), and target porosity (15%, 18%, 21%). The 7-day unconfined compressive strength, permeability coefficient, and elastic modulus were selected as evaluation indices. Response Surface Analysis (RSA) and Analysis of Variance (ANOVA) were applied to determine the optimal mix proportion. Scour resistance tests were conducted based on the optimal mix design to analyze the effects of scour time, frequency, and impact force on strength and modulus variation. The results indicate that the optimal mix ratio is Grade I, with a water-cement ratio of 0.35 and a target porosity of 18%. This yielded a 7-day compressive strength of 5.1 MPa, a rebound modulus of 2170.7 MPa, a permeability coefficient of 49 mL/s, and a hydraulic conductivity of 0.0027–0.0054 m²/s. Under standard scour conditions, compressive strength, splitting strength, dynamic rebound modulus, and splitting rebound modulus decreased by 16%, 33%, 40%, and 16%, respectively. Compared to cement-stabilized gravel (53% strength loss), pervious concrete exhibited lower strength loss (16%) due to its interconnected porosity, which mitigates internal water pressure during scouring. Overall, pervious concrete outperforms cement-stabilized gravel in mechanical properties and scour resistance, providing theoretical guidance for engineering applications. Full article

The expansion of urban impervious surfaces exacerbates flooding risks, influenced by both impervious surface coverage (ISC) and its spatial distribution. To investigate the impact of urban land use layouts on stormwater runoff, this study examined the current land use conditions in the Xinling Bay watershed of Xiamen, China, and generalized land use into three ISC classes: impervious (I, ISC = 100%), semi-pervious (S, ISC = 50%), and pervious (P, ISC = 0%). Six spatial layouts (ISP, IPS, SIP, PIS, SPI, and PSI) were modeled using SWMM under varying rainfall intensities and land unit scales. The influence of ISC layouts on peak runoff, peak time, and total runoff was simulated. The results indicate: (1) The IPS spatial layout yields the most effective stormwater mitigation; (2) Prioritizing impervious land upstream while avoiding pervious units upstream minimizes runoff; (3) Layout effects weaken with higher rainfall intensity but strengthen with larger scales. These findings provide actionable strategies for sustainable urban planning to enhance flood resilience through spatial distribution optimization. Full article

As a type of green stormwater infrastructure (GSI), stormwater parks play a crucial role in mitigating urban heat and managing stormwater, especially in subtropical monsoon climates where high temperatures and rainfall coincide. The benefits of microclimate improvement are associated with the specific surface types of stormwater parks. However, research on how different surfaces affect the microclimates of stormwater parks remains limited. This study utilized an unmanned aerial vehicle to investigate the surface temperature characteristics of blue–green–gray underlying surfaces within a stormwater park and employed multiple linear regression to analyze their impact on the microclimate. The results indicated that (1) blue underlying surfaces functioned as a stable cold source in dry periods but warmed quickly after rainfall. (2) Green surfaces consistently provided a cooling effect on the microclimate, with cooling intensity intricately related to vegetation structure. Specifically, the cooling effects of arbor–shrub–grass and arbor–shrub combinations were greater than those of other plant configurations. (3) The warming effect of gray underlying surfaces was affected by weather conditions and permeability, with pervious concrete exhibiting lower surface temperatures than impervious pavements during dry spells, although this difference diminished significantly after rain. These findings provide scientific evidence and design guidance for enhancing the sustainability of microclimates. Full article

Impervious areas are one of the important indicators for evaluating the urbanization process, while surface temperature is one of the reference factors for evaluating the urban environment. In order to investigate whether the spatial distribution of an impervious surface has any influence on urban surface temperature, Xuzhou City was selected as the study area, and the impervious surface information was extracted based on the maximum likelihood classification method for Xuzhou City for the period of 2013–2022, and surface temperature inversion was performed using Landsat 8 remote sensing imagery and nighttime lighting data. In order to reduce the confusion between bare soil and impervious surfaces, the study area was divided into built-up and non-built-up areas for the selection of impervious and pervious surface samples using nighttime lighting data, and, finally, the maximum likelihood classification method was used to realize the extraction of impervious surfaces. The experimental results show that, by extracting the impervious surface of Xuzhou City, the impervious surface of Xuzhou City continued to increase from 2013 to 2022, in which the growth rate was faster in 2014–2016 and 2019–2021, and slower in 2017–2018 and 2021–2022, after performing surface temperature inversion as well as temperature grading. The results of impervious surface extraction and surface temperature inversion were subjected to overlay analysis and linear regression analysis. It was found that most of the impervious surface area is in high-temperature areas, and the density of the impervious surface is proportional to the surface temperature in the impervious surface and its surrounding area. Therefore, it can be concluded that the expansion of impervious surfaces is one of the reasons for the increase in urban surface temperature. Full article

This study investigates the performance of sludge-added pervious concrete (SPC) at different curing temperatures by replacing some of the cement with activated sludge (AS). The results reveal that the incorporation of AS into pervious concrete had a favorable impact. At a curing temperature of 30 °C, the 28-day compressive strength and specific surface area reached 20.8 MPa and 9.14 m²/g, respectively, representing a 60% and 98.7% increase, in comparison to conventional concrete. Furthermore, the addition of AS to the concrete results in a notable reduction in the concentration of chemical oxygen demand (COD) in surface runoff water. The maximum rate of COD removal observed was 55.6%. A mechanism study revealed that the strength of concrete increased due to the reaction between reactive SiO₂ in AS and CaO in the aggregate. At a temperature of 30 °C, the microorganisms in the activated sludge fermentation process exhibit a higher production rate of fermentation gas, resulting in a greater escape of gas and an increase in the number of micropores in the permeable concrete. This leads to an enhanced specific surface area, which in turn exhibits a superior adsorption effect on COD. Full article

In recent years, various aspects of research related to pervious concrete (PC) have progressed rapidly, and it is necessary to summarise and generalise the latest research results. This paper reviews and compares the raw materials of pervious concrete, examining elements such as porosity, permeability, mechanical properties, and durability. According to comparisons, we put forward an ideal aggregate model with Uneven Surface, which may reinforce the mechanical properties. By summarising the important issues of aggregate, particle size, water–cement ratio, additives and admixtures, mixing ratio design, mixing and moulding, and other factors that affect porosity, new design methods are proposed. A new effective stress model of pervious concrete based on continuous porosity and Terzaghi effective stress is developed which may fit the effective stress principle better. Finally, by summarising the research frontiers of pervious concrete, key issues that need to be addressed in future scientific research on pervious concrete are raised. Full article

Pervious concrete is desirable for water drainage in building systems, but achieving both high strength and good permeability can be challenging. Also, the importance of compaction energy is significant in determining the efficiency of pervious concrete. However, research on the development of unconfined compressive strength (UCS) prediction models for pervious concrete materials that incorporate compaction energy parameters remains unexplored. Therefore, this study aimed to balance strength and permeability while optimizing the compaction energy required for concrete production. A Central Composite Design (CCD) was used to design experiments within the response surface methodology (RSM) and evaluate the UCS, the porosity and permeability of pervious concrete specimens produced with varying cement content (280.00–340.00 kg/m³), the water-to-cement ratio (0.27–0.33), the aggregate-to-cement ratio (4:1–4.5:1), and compaction energy (represented by VeBe compaction time, 13–82 s). A regression model with goodness of fit (R²_adjusted > 0.87) was calibrated to estimate the UCS of pervious concrete as a function of mix design parameters and VeBe compaction time (T_vc). This model can potentially guide field practices by recommending compaction strategies and mix designs for pervious concrete, achieving a desirable balance between mechanical strength and hydraulic permeability for building construction applications. Full article

Due to the high uncertainty of model predictions, it is often challenging to draw definitive conclusions when evaluating river water quality in the context of management options. The major aim of this study is to present a statistical evaluation of the Hydrologic Simulation Program FORTRAN (HSPF), which is a water quality modeling system, and how this modeling system can be used as a valuable tool to enhance monitoring planning and reduce uncertainty in water quality predictions. The authors’ findings regarding the sensitivity analysis of the HSPF model in relation to water quality predictions are presented. The application of the computer model was focused on the Ave River watershed in Portugal. Calibration of the hydrology was performed at two stations over five years, starting from January 1990 and ending in December 1994. Following the calibration, the hydrology model was then validated for another five-year period, from January 1995 to December 1999. A comprehensive evaluation framework is proposed, which includes a two-step statistical evaluation based on commonly used hydrology criteria for model calibration and validation. To thoroughly assess model uncertainty and parameter sensitivity, a Monte Carlo method uncertainty evaluation approach is integrated, along with multi-parametric sensitivity analyses. The Monte Carlo simulation considers the probability distributions of fourteen HSPF water quality parameters, which are used as input factors. The parameters that had the greatest impact on the simulated in-stream fecal coliform concentrations were those that represented the first-order decay rate and the surface runoff mechanism, which effectively removed 90 percent of the fecal coliform from the pervious land surface. These parameters had a more significant influence compared to the accumulation and maximum storage rates. When it comes to the oxygen governing process, the parameters that showed the highest sensitivity were benthal oxygen demand and nitrification/denitrification rate. The insights that can be derived from this study play a critical role in the development of robust water management strategies, and their significance lies in their potential to contribute to the advancement of predictive models in the field of water resources. Full article

In order to meet the needs of low-impact development and sustainable development, there is an urgent desire to develop an innovative recycled aggregate pervious concrete (I-RAPC) that is of high strength and permeability. In this study, I-RAPC was prepared based on response surface methodology (RSM) using recycled aggregate, river sand, and different types of pipes as the materials, and the effects of different pipe parameters (number, diameter, material, and distribution form) on the performance of I-RAPC were investigated. In addition, the calculation model of the compressive strength and the permeability coefficient of I-RAPC were proposed. The results showed that the frontal- and lateral-compressive strengths of I-RAPC were 39.8 MPa and 42.5 MPa, respectively, when the pipe material was acrylic, the position was 1EM, and the diameter was 10 mm—at which time the permeability coefficient was 3.02 mm/s, which was the highest in this study. The maximum relative errors of the compressive strength calculation model and the permeability coefficient calculation model were only 7.52% and 4.42%, respectively, as shown by the post hoc test. Therefore, I-RAPC has the advantages of high strength and permeability and is expected to be applied in low-impact development in cities with heavy surface sediment content and rainfall. Full article

Urbanization and climate change have led to rising urban temperatures, increasing heat-related health risks. Assessing urban heat risk is crucial for understanding and mitigating these risks. Many studies often overlook the impact of block types on heat risk, which limits the development of mitigation strategies during urban planning. This study aims to investigate the influence of various spatial factors on the heat risk at the block scale. Firstly, a GIS approach was used to generate a Local Climate Zones (LCZ) map, which represents different block types. Secondly, a heat risk assessment model was developed using hazard, exposure, and vulnerability indicators. Thirdly, the risk model was demonstrated in Guangzhou, a high-density city in China, to investigate the distribution of heat risk among different block types. An XGBoost model was used to analyze the impact of various urban spatial factors on heat risk. Results revealed significant variations in heat risk susceptibility among different block types. Specifically, 33.9% of LCZ 1–4 areas were classified as being at a high-risk level, while only 23.8% of LCZ 6–9 areas fell into this level. In addition, the pervious surface fraction (PSF) had the strongest influence on heat risk level, followed by the height of roughness elements (HRE), building surface fraction (BSF), and sky view factor (SVF). SVF and PSF had a negative impact on heat risk, while HRE and BSF had a positive effect. The heat risk assessment model provides valuable insights into the spatial characteristics of heat risk influenced by different urban morphologies. This study will assist in formulating reasonable risk mitigation measures at the planning level in the future. Full article