How Philly can avoid flooding like Houston's after Hurricane Harvey

Residents used a boat to evacuate a Houston neighborhood inundated by water after Hurricane Harvey.

Anyone who refuses to connect urban sprawl to the increased flooding from storms spawned by climate change wasn’t paying attention to what happened in Houston, where millions are struggling to recover from Hurricane Harvey. A similar fate confronts Miami, where residents in Hurricane Irma’s path are being evacuated.

An overabundance of paved surfaces that prevent rain from immediately soaking into the ground are a problem for Philadelphia, too, but the city has been working on the problem for years and is ahead of many peers in storm water management and drainage.

Even the rebuilding of I-95 through the city has a smart, green edge to it. PennDot is installing 70 “rain gardens” along the route, instead of exacerbating the problem by paving over embankments.

Staff writer Frank Kummer reported that Villanova and Temple professors are working with to keep rain water from spilling off the highways into the city’s storm water system, which would increase flooding in surrounding neighborhoods.

The project may seem simple, but is being carefully planned down to the thinnest blade of grass.

Sasha Eisenman, a landscape architecture and horticulture professor at Temple, evaluated 7,000 plants to find the most suitable to strain road salt and petroleum residues. Black-eyed susan, sumac, pussy willow, black willow, and switchgrasses were among the most effective.

Robert Traver, chair of Villanova’s Urban Stormwater Partnership, collects data from a weather station improvised for the project to measure wind, sun, and rain. That will help evaluate the gardens’ effectiveness and gauge how much maintenance is required.

The city has planted dozens of other gardens, including one near the zoo. Besides absorbing rain water, they help cool the neighborhoods around them. In Fishtown, resourceful residents are using their garden like a park.

The city encourages building owners to plant vegetation on roofs to help cool buildings naturally and absorb carbon dioxide, a harmful greenhouse gas. It also is installing pervious pavements on streets, which let water soak through the surface to underground reservoirs, where it is held temporarily before infiltrating soil.

Even with these measures, the city could learn from others. For example, Philadelphia has only a few curbside gardens while New York has begun a $2.4 billion, 20-year project to create many more. But New York also can learn from Philadelphia, which charges developers a fee to cover the cost of controlling the runoff their structures create. Philadelphia also offers grants to developers employing green technology.

Expanding on its green initiatives and retrofitting a very old city with too many impervious surfaces is Philadelphia’s challenge. Meeting it will require another kind of green — money. No help can be expected from the Trump administration, which would rather deny climate change than fight it.

Raising water rates and fees would be unpopular, but should be considered if it can pay for steps to avoid a flooding disaster like Houston’s, which was worsened by having pavement where there should be grass.

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