**1. Introduction**

The increase in the frequency of flooding in urban areas related to the increase of impermeable surfaces highlights the inadequacy of traditional urban drainage systems. According to Min et al. [1], it is expected that the frequency of high intensity and short duration rainfall events will increase in the coming decades as a consequence of climate change. Wasko and Sharma [2] identified a strong correlation between peak precipitation intensity and high temperatures, and concluded that global warming may lead to an increase of floods of short duration. In addition, Luo et al. [3] report that flash floods have occurred more frequently in Asian cities, with recent increases in urbanization and extreme rainfall, causing significant damage to infrastructure, communities and the environment. This increase in the number of floods shows that it is necessary to use sustainable urban drainage systems capable of restoring the natural hydrological cycle in urban areas and allowing an increase in evapotranspiration and infiltration capacity. Permeable pavements are examples of systems that fulfill this function [4].

According to Scholz and Grabowiecki [5], the managemen<sup>t</sup> of stormwater in urban areas was observed in a more ecological way due to the emergence of sustainable drainage systems that collect, store, treat and redistribute or recycle water. Compared to the traditional drainage system, stormwater retention and infiltration is a sustainable and cost-effective process, which is suitable for urban areas. In addition, these systems have benefits such as the reduction of runoff, groundwater recharge, saving water through recycling, and preventing pollution.

Permeable pavements are considered sustainable drainage systems because they are pavements that support the demands of mechanical efforts and at the same time allow the percolation and temporary accumulation of water, reducing surface runoff without causing damage to their structures [6]. Several studies have shown the advantages of using this type of pavement. In comparison to conventional pavements, permeable pavements provide runoff reductions of up to 42% [5]. According to Pagotto et al. [7], the quality of stormwater is improved by the use of permeable pavements for most pollutants. Heavy metals are reduced by up to 74%, solids are retained at a rate of 87% and hydrocarbons are intercepted at an even higher rate (90%).

Brattebo and Booth [8] examined the long-term efficacy of four permeable pavement systems in the United States. The study showed a significantly better performance for permeable pavements, both for water quality, which had lower toxic levels, and for stormwater infiltration. In the four systems, practically all of the precipitation was infiltrated. The levels of copper and zinc obtained in the water samples collected from the conventional asphalt concrete runoff were alarming: toxic concentrations were reached in 97% of the samples. However, in 31 out of 36 water samples infiltrated in permeable pavements, the concentrations were below the detectable toxic level.

According to Maiolo et al. [9], there is a need to have a methodology capable of providing an accurate estimate of the sustainability of drainage systems. In fact, this assessment may not only be tied to environmental benefits related to lifespan, but assessments are necessary in the steps that precede and follow the lifespan. A valid criterion for the verification of the sustainability of a product or system is the life cycle assessment (LCA). LCA presents an opportunity to evaluate and compare projects and choose the most appropriate drainage systems, quantifying a variety of environmental impacts and benefits. LCA has been effectively applied to assess the environmental performance of the water infrastructure, including the environmental impacts associated with the construction, maintenance and disposal of various green infrastructure technologies, such as permeable pavements [10]. This assessment is based primarily on the amount of greenhouse gas emissions, as well as the consumption of energy and natural resources. Some parameters significantly affect the evaluation, such as local climatic patterns, regulatory requirements, quality of infiltrated stormwater, lifespan and treatment efficiency of the systems [11].

As stated by the Electric Power Research Institute [12], at a national scale, the transport and treatment of water and wastewater accounts for nearly 4% of the US electricity demand. Such dependency of water infrastructure on electric utility infrastructure leads to serious environmental impacts. In this way, decentralized water managemen<sup>t</sup> brings benefits not only as a means of reducing stresses on the water treatment infrastructure but also as a strategy to reduce the demand that water companies impose on the regional energy system, and on reducing the carbon footprint [13]. As a point of reference, the City of New York [14] estimates that systems of water treatment, supply, and sewage along with the methane escaping into the atmosphere (generated by the sewage treatment process) add up to 17% of New York's greenhouse gas emissions.

De Sousa et al. [15] evaluated the environmental performance of green infrastructures (permeable pavements and bioretention basins) by comparing them to water storage and treatment scenarios using traditional drainage systems (grey infrastructure). The results showed that green infrastructures emitted 75% to 95% less greenhouse gases, mainly due to the lower use of electricity during the life cycle. Wang et al. [11] showed by means of a case study in China that 73.48% of energy consumption, 46.70% of greenhouse gas emissions, 98.33% of lead emissions and 99.70% of zinc emissions could be avoided by using permeable pavement instead of conventional pavement.

While understanding the life cycle implications of sustainable drainage systems is only in its early stages, LCA studies are important in guiding planning and decision-making when considering multiple objectives such as increased water resources and reduction of natural disasters and environmental impacts [16]. Thus, the objective of this paper is to present an overview of permeable pavements and show studies of LCA that compare the environmental performance of permeable pavements with traditional drainage systems, in order to provide scientific instructions for the choice of more

sustainable drainage systems and thus improve the sustainable managemen<sup>t</sup> of stormwater in urban areas.
