Seeking ways to prevent flooding caused by climate change

As climate change continues to intensify, urban planners are constantly seeking innovative ways to prevent flooding caused by heavy downpours. Techniques such as planting rain gardens and installing green roofs have been implemented in various cities. 

However, a recent study conducted by University of Cincinnati geography students in collaboration with the Hamilton County Conservation District suggests that a simple hole in the ground, known as a detention basin, can be just as effective.

Man Qi, a doctoral student at the UC College of Arts and Sciences, led the study. She explained that cities are constantly developing new ways to trap rainwater and direct it where it is most needed, especially during droughts. These methods, called low-impact development practices, include innovations like permeable pavement, which allows rainwater to seep into the ground instead of being diverted elsewhere. 

Another such innovation is the bioretention cell, which consists of ornamental or landscaping plants atop soil designed to drain quickly, spread over a thick bed of gravel for optimal absorption. These cells can soak up large volumes of rain without creating standing pools of water.

Urban planners must consider how to prevent rainwater from spilling onto neighboring properties or roads when designing commercial or housing developments. Hard surfaces like buildings and parking lots cannot absorb heavy rains, necessitating the collection or diversion of water to avoid property damage. 

“A detention pond is a common practice. It temporarily stores the water and releases it into the air or the groundwater or nearby streams at a low rate to reduce the risk of flooding. It also provides some ecological benefits,” said Qi.

Working with the Hamilton County conservation district, the researchers assessed the effectiveness of flood-prevention techniques such as detention basins and bioretention cells under five different scenarios. The results were presented at the annual American Association of Geographers’ conference in Denver. 

Qi explained that in residential areas where the impervious area is less than 40 percent, low-impact development practices are better. “But if 70 percent or more of the ground surface is impervious, it’s best to put in detention basins. The flood risk can be greatly reduced.”

Climate change is expected to increase the frequency and severity of rainstorms, making deliberate drainage planning even more crucial for cities. Professor Lin Liu, a study co-author and co-director of UC’s Joint Center of GIS and Spatial Analysis, elaborated on this issue: “Global warming and urban sprawl have contributed to extreme weather. Coupled with the urban heat island effect, many metropolitan cities have experienced more extreme precipitation events. As a result, urban flooding has become an increasing threat to the loss of human life and property damage in many cities around the globe.”

‘Intense, heavy rains could inundate networks designed to prevent flooding, and the capacity of drainage networks could fail because they simply can’t hold that much stormwater,” said Qi, who experienced the reality of urban flooding firsthand in 2021 when her sister’s home was flooded in China’s Zhengzhou City. The disaster affected more than 10 million people, killing nearly 400 and causing $10 billion in property damage.

Urban flooding disproportionately impacts lower-income residents who lack the resources to recover quickly from disasters. Flood insurers create maps based on once-in-a-century disasters, but due to climate change, these events are becoming more frequent. 

Qi emphasized the widespread consequences of flooding, noting that it “affects roads and infrastructure and interrupts society. Schools are closed. Businesses are closed. The impacts are widespread.”

As climate change exacerbates the risk of urban flooding, it is essential for planners to consider innovative and effective strategies like detention basins to protect lives, property, and the environment.

Climate change and sea level rise will have significant impacts on cities, especially those located in coastal areas. Some of the primary consequences include:

1. Flooding: As sea levels rise, low-lying coastal cities will experience more frequent and severe flooding. This will lead to disruptions in transportation, damage to infrastructure, and potential loss of life and property. Inland cities may also face increased flooding due to more intense precipitation events caused by climate change.
2. Infrastructure damage: Rising sea levels and storm surges can erode coastlines and damage critical infrastructure, such as bridges, roads, ports, and power plants. This damage can disrupt essential services, leading to economic losses and potentially impacting public health and safety.
3. Saltwater intrusion: As sea levels rise, saltwater can infiltrate freshwater sources, including rivers, aquifers, and wells, making them unsuitable for drinking, agriculture, and industrial use. This could exacerbate water scarcity issues in many cities, especially those already struggling with water management.
4. Loss of land: Coastal cities may experience a loss of land due to erosion, submersion, and permanent inundation as sea levels rise. This can lead to displacement of residents, loss of property, and shrinking tax bases, putting additional pressure on city budgets.
5. Human displacement and migration: As climate change and sea level rise make certain areas uninhabitable, people will be forced to relocate, leading to increased migration and potential conflicts over resources in receiving communities. This will put additional strain on social services, housing, and infrastructure in the cities where these migrants relocate.
6. Public health risks: Warmer temperatures associated with climate change can exacerbate air pollution and facilitate the spread of vector-borne diseases like malaria and dengue fever. Additionally, extreme heat events can lead to heat stress, dehydration, and heat-related illnesses, especially among vulnerable populations such as the elderly, children, and those with pre-existing health conditions.
7. Economic impacts: Climate change and sea level rise can negatively affect a city’s economy through disruptions in trade, tourism, and industry. Damage to infrastructure and property, along with increased insurance costs, can also strain local economies.
8. Ecosystem disruption: Climate change and sea level rise can disrupt coastal ecosystems, leading to the loss of essential habitats and services, such as natural flood protection from wetlands and storm surge buffering from barrier islands.

To mitigate these impacts, cities need to develop and implement comprehensive adaptation and resilience strategies, including improving infrastructure, implementing nature-based solutions, promoting sustainable urban planning, and investing in early warning systems and disaster risk reduction measures.

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