American Oceans

How Does Stormwater Runoff Affect the Environment

In an ever-changing environment, many of us might associate rain with all good things such as life and vitality. What about stormwater runoff?

stormwater runoff affect rain to flow in environment

While plant life may absorb the majority of rain, what happens to the excess water that isn’t used up? Though stormwater runoff may sound fairly harmless, it poses a threat to the environment and the health of the public.

So what specific issues can stormwater runoff cause? Who causes it? And how can we reduce its negative impact?

Let’s start with the basics and delve into what is classified as stormwater runoff. Read on to learn about the numerous effects of stormwater runoff and how they can be avoided.

What is Stormwater Runoff?

Have you ever seen the small streams of water running down the streets during or after a storm? This is an example of stormwater runoff.

stormwater runoff flow across gutters and sewers

Runoff is any water that isn’t absorbed by the environment and is left to flow across the land.

This water eventually reaches gutters or sewers where it will then travel to the nearest body of water. 

Is stormwater runoff good or bad?

Though stormwater runoff presents many risks to the environment and communities, it’s important to note its effects are not all bad. For example, stormwater runoff replenishes bodies of water, groundwater, and contributes to the natural erosion of land.

What Causes Stormwater Runoff?

Though there are some factors that increase stormwater runoff, it is clear that the main cause of stormwater runoff is the natural cycle of precipitation.

precipitation cycle causes stormwater runoff

As urban areas have continued to develop, the occurrence of runoff has risen. This is because many areas such as these contain little exposed soil.

More specifically, the construction of buildings, parking lots, sidewalks, streets, and other impermeable surfaces prevent the soil below from absorbing any runoff.

Who is responsible for stormwater runoff?

It’s difficult to pinpoint a specific source of stormwater runoff. In reality, many of us are contributors to runoff without even knowing it.

Any form of litter that ends up on the ground can lead to the negative effects associated with stormwater runoff.

Stormwater runoff often picks up pollution left behind by cars, construction, pets, dumping, spills, fertilization, and everyday citizens. In other words, many may be blissfully unaware that their actions are harmful.

For example, the U.S. Environmental Protection Agency estimates 193 million gallons of oil are improperly disposed of every year by American households.

Issues Associated with Stormwater Runoff:

It’s important to address that even small amounts of runoff can affect the environment negatively. In addition to the environment, the frequency of stormwater runoff can be potentially dangerous for people and animals in the surrounding community. 

How does it affect the environment?

In order to understand how stormwater runoff affects the environment, we must first look back at the ways in which it travels.

As mentioned above, stormwater runoff flows over man-made structures in communities. As you can imagine, these structures may contain or host many harmful substances.

These substances may include: oil, metals, pesticides, bacteria, soil, soap, fertilizers, chemicals, or any other material you can imagine might fall on the ground. 

As these materials are picked up by stormwater runoff and carried through storm drains, they are deposited into lakes, oceans, rivers, and other bodies of water.

Simply put, stormwater leads to excess pollution in the environment. Additionally, stormwater runoff can cause floods or even water shortages.

If there is too much runoff, the water that drains into nearby bodies of water can be overfilled. As a result, surrounding communities may experience floods. 

On the other hand, because man-made structures prevent stormwater from being absorbed by the soil and plants in an area, there can be a water shortage within the community as groundwater is not replenished.

How does it affect animals?

When it comes to pollution, the environment and wildlife go hand in hand. It may be obvious that aquatic wildlife is affected by stormwater runoff, however, land-bound animals can be affected too. 

As stormwater runoff collects debris and pollutants from the surrounding area, it travels toward many animals’ natural habitats such as a lake or ocean.

These substances are often toxic to wildlife and can lead to their death. Even minute amounts of substances can affect wildlife.

For instance, an ounce of bleach needs to be diluted by 312,000 ounces of water to be safe for animals. 

Likewise, any floods that occur can overwhelm the delicate balance of an ecosystem and harm or kill animals. 

Materials such as drink-holding plastic loops and cigarettes are frequently found within bodies of water due to runoff.

These loops can strangle the animals while cigarettes may be consumed and sicken them. When it comes to non-aquatic animals, these creatures are affected in an indirect yet similar manner.

Floods within an area can also cause land-bound animals trouble as they may not be equipped to survive in water. 

In addition to this, water in lakes or rivers are often the main source of hydration for many animals. If this water is polluted and wildlife drinks it, it may also harm or kill them. 

How does it affect people?

So, we know stormwater runoff affects the environment and animals, but what about us? Believe it or not, stormwater also presents risks to humans.

This is primarily caused by the effects runoff can have on water quality within an area. Similar to all other life forms, the floods often caused by stormwater runoff can also put people in surrounding communities in danger.

Though it may not seem very extreme, some of these floods can lead to property loss, injury, and even drowning. 

Though the impact stormwater runoff can have on one’s health may seem the most vital, it is important to note that this form of pollution can also impact other areas of peoples’ lives. 

Specifically, damage from floods can be very expensive to clean up and can affect the financial well being of an area.

Correspondingly, runoff can lead recreation, fishing, shellfish, and tourism businesses to face financial hardships. This can of course affect the overall revenue in the area and affect the economy. 

Lastly, the excess pollution stormwater runoff can create in bodies of water can lead to an increase in water treatment costs.

How does it affect water quality?

As mentioned previously, stormwater poses a threat to people as it affects water quality. But how does this happen? And should you be concerned? 

stormwater runoff affect dirty water quality

As you might know, many bodies of water are used to provide drinking water for the population.

However, as stormwater runoff continues to be a problem, our drinking water may continue to be unsafe. 

While you might think the amount of pollutants couldn’t possibly be high enough to make the water unsafe, Puget Sound streams, in Washington state, were found to contain 23 different pesticides.

The combination of pollutants found in stormwater runoff, including bacteria from septic systems and pet feces, makes these bodies of water much harder to treat to be safe to drink.

This can, of course, lead to health issues for those who consume it if not treated properly. Surprisingly, even being in contact with polluted water can be dangerous.

For example, swimming in waters infected by stormwater runoff can make individuals sick. This sickness can lead to issues such as fever, rash, diarrhea, and sinus problems.

Though the water itself may not be a concern, it is essential to remember that some of the foods we eat (such as fish) also live in this polluted water.

As the animals absorb the chemicals and pollutants in this water, they may become unsafe to eat. 

How Can We Reduce Stormwater Runoff?

After hearing all of the problems stormwater runoff can cause, you may be feeling overwhelmed and maybe even a little scared.

Although the issue of stormwater runoff is serious, the good news is we can all do our part to reduce the negative effects runoff can have. 

Changes you can make include:

  1. Limited driving and frequent car maintenance to avoid oil leaks. 
  2. Be sure to clean up after your pets.
  3. Maintain your septic system if you have one.
  4. Try to avoid using products that contain pesticides.
  5. Be sure to avoid littering and clean up trash when you can.
  6. Don’t dump trash or litter into gutters.


Stormwater runoff is certainly a complex issue; though necessary in some ways, it is also disastrous in others.

This problem is often one that is overlooked or even unheard of by many individuals. It is essential that we all do our part to understand the impact stormwater runoff can have and educate others around us.

With some simple changes, it is possible to reduce the detrimental effects of stormwater runoff.

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