Surface water flooding prevention remains a significant concern for engineers, especially as weather events become increasingly severe and often reveal the inadequacy of the affected infrastructure. When rainfall totals exceed what can run off, either from drains and sewers or from natural drainage, water flows over the surrounding land.
Keeping the water levels manageable means being proactive at the start of a project. Engineers must be willing to improve current flood management methods when it becomes evident that the existing ones will no longer suffice. Here are some possibilities.
Use Models to Guide Efforts
Flood models can reveal which areas of countries, states or communities are most at risk for severe water damage in the future. Engineers should strongly consider using them to weigh the pros and cons of building new infrastructure or updating existing features.
Flood Models Enable Better Preparedness
A 2018 study sought to update existing flood modeling data. The findings showed some sobering results, including that there were more people at risk of experiencing floods than was previously thought.
However, Kris Johnson, who coauthored the study, said, “By knowing those places most at risk from floods, we could avoid development in these areas. Protecting floodplains or developing them in ways that can withstand flooding—such as flood-tolerant parks—can prevent unnecessary risk to people and help avoid expensive damage to property and infrastructure. Floodplains also store and convey floodwaters, which can help prevent flooding in nearby communities.”
Models Highlight Water Banking Potential
Elsewhere, a Stanford University team developed models to assess the usefulness of a newer fluvial flood management technique called water banking, which involves complementing surface infrastructure with underground components, such as aquifers.
David Freyberg, the senior author of a paper on the subject and a civil and environmental engineering professor at Stanford, noted, “Integrating managed aquifer recharge with floodwaters into already complex water management infrastructure offers many benefits, but requires careful consideration of uncertainties and constraints. Our growing understanding of climate change makes this an opportune time to examine the potential for these benefits.”
The computer models accounted for climate and hydrological simulations and allowed users to see how conditions would likely change over time through 2090. The modeling software also enabled researchers to see which existing infrastructure would benefit most from the upgrades mentioned above.
Recognize the Potential of Green Infrastructure
Engineers have long used so-called gray infrastructure as a sort of temporary patch for surface water issues. For example, when water swamped a city, the chosen solution might have been to add additional pumping stations with larger drains and more robust pumps. However, University of Pennsylvania researchers believe it’s time to pay more attention to green infrastructure options, such as rain gardens and tree trenches.
That’s an aim of Philadelphia’s Green City Clean Waters program, which launched in 2011. It has so far added green infrastructure to 800 sites around the city. They collectively prevented nearly 3 billion gallons of dirty water from getting into the surrounding rivers.
City officials in Hull, a port city in East Yorkshire, England, believe green spaces are the way forward, too. They noticed that previous efforts, including building new flood walls and a water storage lagoon, fell short of addressing the problem. Some of the upcoming plans feature green areas that hold and release water after downpours. Plus, new buildings will have sustainable drainage systems, while existing ones will receive upgrades that give them water storage capabilities.
Jessica Fox, a flood risk officer with the Hull City Council, highlighted the need to act now before it’s too late. “As the city grows and takes up more of the natural environment, water is going to run out of places to go. It is becoming widely understood that we cannot prevent all flood events from happening, so we need to find new ways of living with water.”
Target Community Needs
Managing current and future surface water flooding requires making people aware of the areas at greatest risk of flooding, giving them the information they need to evacuate promptly and safely. The same is true when construction crews work on flood mitigation projects, such as trenches. Dirt collapsing on a person working inside a channel poses a significant hazard. A cubic yard of soil could weigh as much as a car.
People who build trenches must receive certifications that prove they have the knowledge needed to prevent accidents. However, residents living in areas prone to surface water flooding may not recognize the signs of situations that could endanger their lives. Using signage is a conventional way to warn people of the hazards.
There’s also interest in the idea of protecting people from surface flooding while simultaneously providing the affected communities with desirable amenities. For example, a New York City proposal called The BIG U took that approach to help Lower East Side residents. It suggested using 10 continuous miles of flood protection built according to the typology of individual affected neighborhoods. Complementary work would also occur for social and community planning.
For example, the part of the project stretching from the Brooklyn Bridge to The Battery would feature a maritime or environmental education museum. The result would be an area that’s safer from surface water flooding and more appealing, too. As engineers continue looking for flood mitigation strategies, they should ideally seek methods that keep people safer during emergencies but address their well-being at all other times.
Pursue the Possibilities of Permeable Concrete
Since concrete is widely used in structures and roads, people are often eager to address some of its known shortcomings. For example, work is underway on concrete that can fix itself, greatly improving infrastructure maintenance.
Recent progress also suggests that using porous concrete could be an effective way to stop surface water flooding. A company called AquiPor makes a type of permeable concrete that allows up to 25 inches of rainfall per hour to flow through tiny pores. Each opening is approximately the diameter of a strand of human hair. Internal tests also showed that the little holes restrict about 80 percent of pollution and particulate matter found in stormwater.
Analysts argue that flood-resilient street materials are already used in cities but that they’re not widespread enough. For example, some roads are specially designed with layers of materials like sand and clay underneath them that soak up and temporarily store rainfall. They argue that permeable concrete is still a relatively niche product, making it more expensive than less innovative possibilities.
Adopt a Broader Viewpoint About Funding Resources and Design
When certain strategies seem too expensive to consider, engineers and those responsible for funding their projects must realize that it’s often necessary to invest more in up-front infrastructure costs to prevent future catastrophes. Achieving that shift requires a new mindset, though.
For example, parts of London recently received as much as 1.6 inches of rain in two hours during flooding that made some tube stations inoperable. When commenting on that situation, Stephen O’Malley, a founding director of Civic Engineers, discussed the need to change resource planning and design considerations.
After noting that the affected area had two major flood events during the summer of 2021 within only two weeks, he cautioned, “Authorities right across the U.K. need to be more mindful of the flood risk, there is arguably a myopic approach to these problems [such as flooding], and they are often dealt with one at a time. However, as an engineering profession, we should be looking at overlapping inter-dependent systems and networks.”
The benefits of such a shift could become apparent outside of the United Kingdom, too.
O’Malley continued, “Sadly, that’s not how funding is determined or how design is developed and implemented, which I think is a real missed opportunity.” He also confirmed that the issue was not that the affected transit stations failed to meet regulations during their construction. They all complied with such necessities at the time, but changing circumstances often require reassessing old methods.
“I think the blind spot has been that, when it comes to these extreme events, you are not going to be able to ameliorate or accommodate all the flooding, nor should you spend the money to accommodate all such extreme events. But you can design infrastructure in a way that it recovers or can recover faster and does not experience too much damage,” O’Malley offered.
Proactive Strategies Are Crucial
These suggestions highlight how there’s no single solution to curb surface water flooding. However, taking the time to consider current and future needs and staying mindful of the parties affected by infrastructure changes will help engineers focus on the best ways forward.