When Cities Drown: The Unique Dangers of Urban Floods

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Navigating the Hazards of Urban Floods: Stay Safe with These Tips

Floods are the most common natural disaster in America and are considered as being caused by general climate change. Also, cities are already witnessing the impacts of climate change-induced disasters such as flooding, water stresses in summer, intense rainfall-induced landslides, and strong typhoons.

Being a natural calamity, flooding is an inevitable disaster that occurs even in an urban setting. As one of the biggest challenges in many parts of the world which take place each year, urban flooding rears its ugly head in various forms due to several reasons such as high-intensity rainfall, poor drainage, and organic factors like high tides. Regarded as one of the most natural disastrous events that result in unimaginable losses and damages, it is best that we fully understand why floods in urban areas are particularly dangerous.

In much of the United States, urban flooding is occurring increasingly for the last 10 years now and is a growing source of significant economic loss, social disruption, and housing inequality. However, every city in the U.S., from small towns to major metropolitan areas, can be at risk of flooding due to urban sprawl and a changing climate. We’re not just talking about the big major disasters like Hurricane Katrina in New Orleans, which caused 1,800 deaths and $125 billion in damage in late August 2005, but also smaller ones which, however, are causing in sum a vast amount of damage.

Read more about how far inland can hurricanes go in our post.

What is Urban Flooding?

The Federal Emergency Management Agency defines urban flooding as
“the inundation of property in a built environment, particularly in more densely populated areas, caused by rain falling on increased amounts of impervious surfaces and overwhelming the capacity of drainage systems. It excludes flooding in undeveloped or agricultural areas. It includes situations in which stormwater enters buildings through a) windows, doors, or other openings; b) water backup through pipes and drains; c) seepage
through walls and floors.”

What Causes Floods In Urban Areas?

Often, urban flooding occurs when rainwater flows into an urban area at a much higher rate. While such inundations can be absorbed into the ground or moved to a water reservoir, the increased flow of water can become serious as it can adversely affect or even claim lives. Let’s take a quick look at some of the reasons why floods would abruptly surge into urban areas.

Environmental Factors

No doubt, global warming has resulted in extreme weather conditions that have significantly increased the flood risk. While it is believed that the changing climate plays a huge role in the heightened occurrence of such devastating floods, some cities’ lack of preparedness and resources remains to be the culprit for these unexpected floods.

Ecological Factors

Highly depending on the type of soil and its capacity to retain water, trees, and vegetation can reduce the flood water’s speed, helping avoid heavy damage to both life and property. Although soil erosion and deforestation are simply the results of rapid urbanization, their effect is the devastating surge of water into urban areas, which at times lead to loss of life.

Human Factors

As more of us encroach into the natural environment, our role in the interference of the smooth flow of water to the drainage systems is unquestionably huge. While it may seem unimportant to most of us, certain tourism and mining activities, particularly those near bodies of water, accelerate the deterioration of our ecosystem. Not only do such negligence and lack of proper governance cause floods, but they can also result in losses on a destructive scale.

Cities and Vulnerability to Floods

Cities are filled with many different hazards, which also makes them especially vulnerable to floods. There are a number of factors that contribute to this vulnerability: lack of natural buffers and water retention areas, dependence on municipal infrastructure like sewage treatment plants or power grids, the existence of hazardous waste sites near the flood zone, and populations living in low-lying areas due to high housing costs.

In an urban area, these problems can be compounded because there is often no escape route for people who live in lower elevation zones; they may not have access to boats or transportation out of the city when it floods, so they will simply stay put until help arrives – but by then it’s too late!

urban flooding causes damage
Urban Floods

As climate change greatly alters the rain patterns across the globe, we face a whole new range of challenges in containing the high levels of rainfall that we experience today. While a handful of communities still fail to take these factors into account as they plan for the future, it may be in everyone’s best interest if we start designing urban areas with these risks in mind.

It’s clear that especially in coastal regions of the United States such as New York City and Miami, urban flood losses will continue to mount. As a national policy problem for years to come it is essential we look at this now so it doesn’t damage our economy further down the line (especially considering the urban growth predicted for the next 10 years).

Why Are Floods In Urban Areas Particularly Dangerous?

Floods occur these days more frequently than ever. While the change in weather patterns and the increase in rain intensity may result in heavy urban flooding, the rising temperature may result in a rise in sea levels. This leads to an increase in flood risk particularly in coastal urban areas. Since instances of flooding around the world have dramatically increased, it is only fitting that we learn the amount of damage it brings to our cities.

Density of Population

Floods are often more dangerous in urban areas than rural ones because of the density of the population. Most urban areas are heavily densely populated with high-rise buildings and many people living in close proximity. The density of the population, coupled with the lack of escape routes for those who are too low to reach the higher ground when a flood occurs, is what makes urban floods so dangerous.

Contamination And Disease

Infectious diseases which include Hepatitis A and certain gastrointestinal infections can quickly spread through contact with surfaces that are contaminated by floodwaters. While overflowing sewerage systems may contain industrial wastes or fecal materials, floodwaters pose risks to human health as they may contain pathogens and toxins that can result in certain illnesses. Also, the often polluted waters brought about by urban floods increase the risk of ear, nose, and throat infections, conjunctivitis, dermatitis, and wound infections.

Landslides or Sinkholes During a Flood Event

Urban flooding is also dangerous because of the risk of landslides and sinkholes.
Landslide risks are exacerbated by construction in or near a landslide zone, where buildings create slopes that lead to instability during heavy rains. Conversely, natural water erosion exponentially increases the chances of an earthquake-induced sinkhole occurring during flooding events.

Giant Urban Sinkhole
Sinkhole swallows five-lane street in Japan

Sickness, Injuries, And Infections

Regardless of how well you can swim, floodwaters are known as a drowning risk. Since these shallow waters can hide hazards such as rocks, tree trunks, grass, and sharp debris, it can lead to bone breaks, serious puncture wounds, and at times, even death.

Urban floods are particularly dangerous because of their unpredictability as well as how quickly they can develop. Although it seems unlikely for the waters to come and damage your business and property, they can flood urban areas and sweep across the city in an instant.

The Social Impacts of Urban Flooding

There is a socioeconomic divide that exists in the way people are affected by urban flooding. The poor, who do not have the resources to invest in flood prevention measures and live at higher risk of being flooded due to living closer to water bodies, experience floods more often than affluent segments of society.

Flooding can be a devastating event for those with low or moderate income, and many are not resilient enough to deal with it. When flooding happens repetitively in the same area over time, their well-being is gnawed away immensely due to a lack of resources like savings or insurance.

The flood is a hard-hitting, relentless force that leaves people and their homes devastated. It’s even harder to keep your head above water when you’re already struggling with the basics: food or shelter.

Flooding doesn’t discriminate; it can strike anyone at any time in life if one isn’t prepared for its inevitable arrival.

Further impact is being unveiled by a study about flood victims in Chicago by CNT found that: “84% suffered stress and 13% ill health. Forty-one percent lost the use of part
of their property, 63% lost valuables, and 74% lost hours of work to clean
up” (see graphic below).

impact of urban flooding When Cities Drown: The Unique Dangers of Urban Floods


Extreme rainfall events are increasing in the United States, especially over the last three to five decades. The National Climate Assessment of 2017 concluded that “heavy downpours are increasing nationally…” and will continue to result in more intense urban flooding unless steps are taken with mitigating their impacts.

As the increase in urban flooding has swept countries across the globe, outdated sewer systems and severe weather patterns play a part in generating dangerously huge floods more frequently. From irresponsible garbage disposal to the thoughtless cutting of trees, nothing puts a bigger threat to our peaceful city lives than the dangers of urban flooding.

See also our post about river disasters and floods.

[Video] The Dangers of Flash Flooding

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Author: Richard
Meet Richard Buettner, the esteemed editor of GeoAffairs, armed with a Master's degree in Geography and sharing his valuable insights through 25 years of dedicated experience in the field.

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