Urban Runoff: How Rainwater Turns To Wastewater

There’s a reason people don’t care for the gutters. Next time it rains in your town, look at the streets—the trash floating downstream, fertilizer- and pesticide-laced grass clippings, the sheen of oil, and then all the chemicals you can’t even see in the mess of it all. Relatively pure rainwater which would otherwise replenish the environment has instead become a poison to it.

Toxic Effects Of Urban Runoff

As humans develop an area, they add an increasing amount of surfaces that water cannot permeate—roads, parking lots, sidewalks, anything built with materials like asphalt, cement and concrete. So when it rains, the water cannot immediately sink into the soil, instead flowing downhill over the surface of the ground. As it does so, it picks up everything on the ground—not just all the trash that ends up in the gutters, but also heavy metals and gasoline from leaky cars, pet waste road salt used for deicing, pesticides and fertilizer from lawns, tar from rooftops, lead from old paint, anything toxic that we leave exposed to the rain.

What happens with all this toxic water? Surprisingly little. Eventually, most of the water makes its way to a storm drain. From here, the vast majority of municipal sewers release this water, untreated, back into the rivers and bays surrounding it. Here it wrecks absolute havoc on the environment, from critters being trapped into six-pack-rings swept away from the local football field to heavy metal toxicity building up in the very fish you catch and eat. Many parks are also placed alongside waterscapes, where many will swim, surf, or just enjoy the water, all while getting their daily dose of environmental poisons—including many deadly bacteria which flourish in such waters. In fact, urban runoff is widely considered to be one of the most insidious forms of water pollution.

Other Deadly Effects

In addition to toxic effects, not allowing natural water percolation decreases the water table in the area. Surrounding wells have to be dug all the deeper, and habitats downhill from the city are more likely to be parched for water.

Many of the pollutants, especially organic ones, rot and take out much of the oxygen in the water. This can lead to water environments so anoxic that fish will slowly suffocate and die. Conversely, algal blooms can appear in areas with a low of urban runoff because of the high nitrogen and phosphate content in the water.

This can also lead to increased flooding: since most of the water is traveling on top of the ground with few ways for it to percolate in, the volume flowing on the surface can grow and grow during a storm to the point where it can even sweep cars away and flood houses up to their gables.

In addition, as stormwater runs over asphalt and other hot surfaces, it typically heats up, enough that once it meets natural bodies of water, the heat shock can kill many nearby fish.

What’s (Not) Being Done

Some effort is being made to reduce the dangerous effects of urban runoff. There are two main approaches:

The first is to decrease the toxicity of surfaces exposed to rain in the first place. This involves a huge span of activities, from discouraging the use of fertilizers and pesticides in lawns to installing “green” roofs to developing less leaky cars.

The second is to decrease the amount of runoff that accumulates. Some cities are attempting to create more wetlands and retention basins, which can function as natural filters for toxins and by spacing them through the city, the groundwater can be replenished as well.

However, the sheer extent of the problem means that, for all the little efforts that cities are making, it’s not enough. The water is getting all the more polluted and most cities instead focus on retroactive cleanup procedures, as opposed to prevention.

How To Get Involved

As a voter and consumer, there is plenty you can do. Make sure to vote on initiatives that would propose more responsible stormwater treatment practices. Green living in general is an important step, but specifically making sure your roof is of nontoxic materials and not using fertilizers and pesticides are the most major things you can do. If your car is leaking in any way, get it checked out and fixed to reduce gasoline and heavy metal leakage. Direct downspouts from your gutter into your lawn, not onto concrete, so that it may soak into the soil. Wash your car either on the lawn or at a car wash, just somewhere where the soiled water won’t just drain into the street. Next time you see water in the gutter, just think: do I want to be swimming in that?-eating fish from that?-drinking that? And do something about it. The individual is the most important environmental institution we have.