philadelphia

Cities and rainwater

September 24, 2024 By EarthWise Leave a Comment

Cities across the country are grappling with the problem that bigger, more frequent rainstorms occurring as a result of climate change are overtaxing the systems put in place to handle stormwater. Cities use a combination of so-called green infrastructure – such as rain gardens and porous pavements – and traditional gray infrastructure, such as pipes, tunnels, and pump stations.

In 2011, Philadelphia drew national attention for its Green City, Clean Waters program that was designed to manage the increasing amount of storm water using mostly green infrastructure. Thirteen years later, the city is experiencing billions of gallons of polluted stormwater overflowing its sewage outfall pipes each year. Green infrastructure is cheaper and faster to build, but it is not coping with increasing rainfall.

About 700 U.S. municipalities, mostly in the Northeast and around the Great Lakes, rely on these combined sewer systems. Based on updated climate projections, many are having to greatly increase gray infrastructure projects that include concrete holding tanks, tunnels, and pipes that can divert and hold onto flows until the rain stops, and water treatment plants can recover. These projects can take decades to implement and cost billions of dollars.

All across the country, cities are going to need to bite the bullet and make large-scale investments in conventional sewage infrastructure and repairs to stop billions of gallons of raw sewage from running into rivers. The increased storms present a daunting challenge for America’s cities.

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Faced With Heavier Rains, Cities Scramble to Control Polluted Runoff

Photo, posted August 29, 2011, courtesy of Reggie via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Sponging up a river

March 20, 2024 By EarthWise Leave a Comment

During the first week of February, an atmospheric river dumped enormous amounts of rain on Southern California. Over the course of four days, Los Angeles received 9 inches of rain. The average annual rainfall in the city is only 14 inches.

But Los Angeles was not the site of a flooding disaster because the city has spent years preparing for this type of deluge by becoming a “sponge city.” By installing lots of green spaces and shallow basins with porous soil, Los Angeles was able to soak up 8.6 billion gallons of water during the storm, enough to meet the water needs of 100,000 people for a year.

Cities covered with impermeable concrete sidewalks and paved areas make storm-related flooding worse because they are unable to absorb water. Instead, the water flows into drains and overwhelms infrastructure.

Natural materials like dirt and plants take in water from storms and can filter it into underground aquifer that cities can then tap into, especially during droughts. Adding green spaces to cities has many other benefits beyond the ability to absorb large amounts of rainwater.

The so-called sponge-city movement is catching on in many other places. Philadelphia is revamping its water systems in a 25-year project that includes green spaces to absorb stormwater runoff. In China, the government has spent more than a decade adding spongy elements to dozens of cities around the country.

Sponge cities are part of a broader effort to combine modern engineering techniques with natural systems. This is known as green-gray infrastructure. Nature knows what it is doing when it comes to flood control as well as to pollution control.

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‘Spongy’ LA Soaked Up Tons of Water From Atmospheric River

Photo, posted December 28, 2011, courtesy of Ron Reiring via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Green Solutions To Storm Water Runoff

July 5, 2018 By EarthWise Leave a Comment

Philadelphia, America’s fifth largest city, has struggled with storm water runoff problems since the days of Benjamin Franklin. The city’s numerous streams that run into the Schuylkill and Delaware Rivers were eventually covered with brick arches or cemented into underground sewers. The network of underground-to-riverfront outfalls through increasingly-larger pipes is pretty much how all U.S. cities have been coping with storm water for over 200 years.