on October 22nd, 2020

In the field of civil and structural engineering, urban stormwater management is a complex and challenging issue. As cities continue to grow, so does the number of impermeable surfaces — those that do not allow water to infiltrate the ground. From concrete sidewalks to parking lots, excess stormwater runoff from these structures can have serious adverse side effects on the surrounding ecosystem.

In more regional areas, rain can soak into the ground to be absorbed and released by plants. By contrast, when rain hits water-resistant surfaces in urban areas, it causes runoff, and water begins to collect sediment, bacteria, oils, metals, and other known pollutants. It has long been a civil engineers' tradition to direct stormwater into nearby systems to be treated at wastewater facilities or discharged directly into waterways.

However, as cities expand, significant precipitation events are having a higher chance of overwhelming stormwater systems. Scientists are warning that the effects of global warming may cause more rain to fall in one storm than an entire year prior. This means that countries with aging or poorly designed infrastructure are falling behind in their ability to manage runoff.

For example, Mumbai, India, has experienced its wettest monsoon season in more than 61 years. Torrential rains halted city life as many establishments, transport links and homes were submerged in waters waist deep. The coronavirus crisis impacted drain cleaning throughout the city, worsening the effects of devastating floods across the city.   

An important legal consideration for most construction projects is to ensure that the final build won’t worsen downstream flooding for a particular area. On the stormwater front of a project, the engineers need to look out for that when runoff does occur, the interventions help:

  • Reduce erosion
  • Minimize pollution
  • Prevent flooding

More water diverting infrastructure is necessary to achieve less flooding and mitigate the amount of water overwhelming a drainage system. One method of stormwater management would be to increase water infiltration through the inclusion of permeable surfaces. This approach would allow stormwater to still reach soil while reducing runoff from urban infrastructure.  

Topmix Permeable is a fast draining concrete pavement solution that rapidly directs stormwater off streets, parking surfaces, driveways and walkways. This efficient approach to stormwater management would help reduce environment impacts, costs and maintenance efforts. Topmix Permeable’s video of their innovative pavement recently went viral online.

Topmix Permeable’s video, while impressive, saw them receiving critique. The concern among some of the online civil engineering community was that sediment buildup would occur rapidly if stormwater and other elements filtered in below the road surface at such speed. They caution that pavement as permeable as Topmix Permeable would require a lot of maintenance, and expert level drainage - making it tough to implement in roadways.

Nonetheless, all permeable pavements should have stone reservoirs below the surface. The stone reservoir is another fine art the engineer must perfect to create effective permeable pavements. The stone reservoir is generally made of uniformly sized stones that create enough gaps underneath the porous surface. It then temporarily stores water when precipitation is occurring and then slowly moves it off. Nevertheless, Topmix Permeable does look like an intriguing development in pavement that could lessen the chance of flash flooding for cities.

The company says their permeable pavement can provide relief to aging stormwater infrastructure inside the cities. Permeable pavement is still considered a new and developing avenue of the civil engineering world. It is to see much more attention as stormwater drainage continues to make headlines due to added precipitation. If some form of it is to be implemented on roadways in the future, it would require careful design features and construction techniques.

Civil engineers will be keeping an eye on the development of permeable pavement. It may appear at their next project build. Several configurations of how to implement permeable pavement are becoming known as engineers try an assortment of different styles. If these kinds of porous pavements can limit the number of floods worldwide, more and more civil engineers will be looking to lay them at their next project.

Prepare for the future of road construction with EIT’s Professional Certificate of Competency in Fundamentals of Road Construction.

Works Cited

Matchar, Emily. “This Concrete Can Absorb a Flood.” Smithsonian.com, Smithsonian Institution, 5 Oct. 2015, www.smithsonianmag.com/innovation/concrete-can-absorb-flood-180956830/.

“Mumbai Records Decade's Highest 24-Hour October Rain, 2nd Highest Monthly Rain in 10 Years.” Hindustan Times, 15 Oct. 2020, www.hindustantimes.com/mumbai-news/mumbai-records-decade-s-highest-24-hour-october-rain-2nd-highest-monthly-rain-in-10-years/story-5DGtX98zNszUW9jkdXMEWK.html.

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