Permeable concrete pavement—keeping your city from flooding.
Release Time:
2020-07-06
Source:
Recently, many cities have once again been inundated by rainfall, suffering significant losses. We wonder whether your city has experienced flooding as well. With the increasing pavement hardening in urban areas—characterized by poorly permeable concrete roads—and the chronic neglect of essential urban drainage infrastructure, existing systems can no longer cope with the rapid runoff generated by intense, short-duration precipitation events, leading to severe “urban waterlogging.” At present, most Chinese cities rely on a rapid stormwater drainage model: 70% of rainfall falls on impervious surfaces, where it simply runs off the surface before being channeled through pipes for swift discharge. Yet even with extensive pipe networks, such systems prove inadequate when faced with heavy downpours. Sponge city development is one of the effective approaches to preventing and controlling urban flooding.
According to statistics from the Office of the National Flood and Drought Control Headquarters in 2015, from 2013 to 2015 an average of 180 cities—including Beijing, Shanghai, Shenzhen, Guangzhou, and Wuhan—were inundated each year, with the number reaching 234 in 2013. Many experts attribute the frequent occurrence of urban flooding to such factors as “prioritizing above-ground development while neglecting underground infrastructure,” “a lack of scientific planning and forward-thinking in urban development,” “insufficient oversight of underground drainage projects,” and “a development mindset and performance-oriented governance approach that emphasize short-term gains at the expense of long-term sustainability.”
In April 2012, the concept of “sponge city” was introduced at the 2012 Science and Technology Forum on Low-Carbon Cities and Regional Development.
In October 2015, the General Office issued the “Guiding Opinions on Promoting Sponge City Construction,” which explicitly stipulates that, through sponge city development, 70% of rainfall is to be absorbed and utilized on-site.
In March 2017, sponge city development was included as a key annual task in the work report.
The drainage system is the moral conscience of a city… Prolonged, large-scale use of conventional gravel-concrete pavements can lead to pavement hardening, reducing the soil’s natural capacity to absorb water and thereby making urban flood control even more challenging. With frequent flooding during heavy rains, the urgent need for sponge-city development has become apparent. Against the backdrop of rapid urbanization, the dramatic expansion of roads and high-rise buildings has disrupted the original aquatic ecosystem through conventional urban development practices. On traditionally paved urban surfaces, surface runoff accounts for as much as 98% to 100%.
Pervious concrete pavement is a key approach in sponge city development. As one of the source-based runoff control measures, it can deliver five of the six core implementation strategies and techniques for sponge cities: infiltration, detention, storage, purification, and drainage.
The top layer of the pavement is made of permeable concrete and incorporates numerous large pebbles, giving it excellent permeability. The second layer consists of a loose gravel base that can store substantial amounts of water, which then gradually percolates into the underlying soil. Permeable concrete ensures strong, durable bonding between the cement paste and the gravel aggregate while leaving sufficient void space between the aggregates; this design not only maintains high permeability but also enhances load-bearing capacity and durability. Compared with conventional impervious pavements, permeable concrete paving helps alleviate urban flooding, supports integrated urban water resource management, enables rainwater harvesting and reuse, and significantly improves the efficiency and performance standards of urban drainage systems. The advent of permeable concrete has brought new hope for addressing urban stormwater challenges.
In addition, pervious concrete offers the ability to purify suspended pollutants in rainwater; it absorbs noise, reducing noise levels by an average of 5 decibels; and it boasts excellent water-storage capacity, significantly lowering urban runoff potential and mitigating the urban heat island effect. It is suitable for pedestrian walkways, park landscape paths, parking lots, residential community roads, and other light-traffic applications. As pervious concrete continues to be promoted and developed, we are confident that in the near future our cities will truly “breathe.”
