When Harvey Came Calling, Stormwater Lessons

Photo from ABC News

Flooding in Texas as a result of Hurricane Harvey.

When it comes to flooding, pavement is the enemy.

Here in America, we love pavement, but pavement doesn't love us, particularly not when it rains.

Pavement, all development really, inserts an impermeable layer between the rain and the ground's ability to absorb it.

According to the Montgomery County Planning Commission, a one-acre parking lot can produce 16 times more water run-off than a one-acre meadow.

So stormwater that would have been absorbed from the soil by plants and trees is, if you're lucky, collected into retention basis to be released into area streams over a period of time.

If you're not lucky, or live in a community with poor planning, the water heads straight into the stream that is, in all likelihood, already struggling to handle the flow from the storm.

And soon enough, it overflows its banks and you're floating a boat down Manatawny Street or in Memorial Park.

In famously "un-zoned" Houston, they are now paying the price of paving as Hurricane Harvey dumps previously un-seen volumes of stormwater on a city that has paved over much of the prairie grass that would once have absorbed a significant portion of it.

CNBC Photo

Flooding from Harvey in Rockport, Texas.

Reading this excellent series of articles published last year by Pro Publica and The Texas Tribune Sunday as news of Harvey (sorry) flooded Twitter, I was reminded of the danger posed by development, and its ensuing pavement, and climate change, which is producing more frequent and more intense storms -- a combination that increases risk to life and property more and more every year.

As the series summarized: "Unchecked development remains a priority in the famously un-zoned city, creating short-term economic gains for some while increasing flood risks for everyone."

In the same way that increasing development near coastlines, or on the barrier islands geologists call "high speed real estate," increases the risk to life and property from increasingly more severe storms and flooding, paving and increased development in flood plains and even outside them along streams and rivers does the same.

Houston has done both and is now paying a price all U.S. taxpayers will share.

You can also read more in this Houston Chronicle series from 2016.

CNN Photo

Flooding in Houston is like nothing seen before.

Because when developers pave over a meadow or forest, they make money and the local tax base increases. But if it is residential development, it does not increase enough to cover the cost of educating the school children it houses, nor does it increase enough for municipalities to pay the clean-up costs for the flooding it causes.

That's when the U.S. taxpayer steps in, providing flood insurance and clean-ups where insurance companies will not because, as experts, they know it's a money loser.

And all too often, it isn't until the flood is your basement, that the risk is made evident. And that's when government is suddenly everybody's best friend, when it's in your own basement.

As the Dallas Morning News reported Saturday, Texas members of Congress are already asking for the federal storm aid they voted to deny the northeast after Superstorm Sandy hit just five years ago.

"With the exception of Houston Rep. John Culberson, all Texas Republicans in Congress at the time voted against the bill. All but three are still in office today," the newspaper reported.

Everyone is happy to have government involvement after a disaster, but not always so much when it's preventing one.

Floodwater is famously filthy and so efforts to control flooding come from the federal government from the standpoint of clean drinking water.

Rainwater washing through streets and yards picks up a smorgasbord of lawn chemicals, car drippings, salt and grit left over from winter road treatments, 

After all, 1,000 square feet of those manicured lawns we all love requires 10,000 gallons of water

Manicured lawns are almost as bad as pavement when it comes
to sending storm run-off into the sewer system.

every summer. Each year, about 80 million pounds of pesticides and more than 100 million tons of fertilizers are applied to American lawns, and suburban lawns shed most of their water, absorbing just a small percentage.

As for the driveways, roads and parking lots that accompany that type of development, their contribution to stormwater run-off includes PAH's -- a chemical sealant based on coal tar called polycyclic aromatic hydrocarbons, a suspected human carcinogen.

As I reported in a series I wrote about water issues several years ago called Ebb and Flow, parking lots that are treated PAHs flush 65 times more polycyclic aromatic hydrocarbons into streams than untreated parking lots.

So under the authority provided in the Clean Water Act, the federal government, at least for now, is requiring municipalities to clean this filthy floodwater water before dumping it into area streams that ultimately provide drinking water to millions.

In Pottstown, that's a big potential cost given that, as Tom Hylton wrote in an essay published in The Mercury, 38 percent of the borough is covered by impervious surface.

Many kinds of coal tar-based pavement sealants
are adding suspected carcinogens to our drinking water.

That's to be expected in an urban setting that has been around for more than a century, but the requirement to clean its stormwater run-off is something new.

Pottstown faces two paths to deal with that requirement, engineering and/or planning. In other words, find ways to clean the water, or prevent it from getting to the streams in the first place.

The engineering side is already underway.

As The Mercury reported last month, the Pottstown Borough Authority is seeking funding for a $200,000 project to remove 52,197 pounds of sediment from Goose Run each year.

That will be accomplished with the installation of two sediment traps, one near Airy Street east of North Hanover Street, and one near Fourth Street, west of North Hanover Street.

And, perhaps more worrisome to those who insist on larger parking lots, the authority is also considering charging a fee for managing stormwater in the same way it charges for managing sewage.

And as aging infrastructure erodes and pollution control requirements increase, the price only escalates.

One 2016 estimate presented to the authority shows an annual cost of as much as $1.42 million to manage stormwater as soon as 11 years from now.

Rain gardens and street trees can absorb
a remarkable amount of stormwater.

As for the prevention side of the equation, one answer is a word often accompanied by expletives here in Pottstown -- trees, or, if you prefer, "green infrastructure."

According to American Forrests, a non-profit conservation organization, "in one day, one large tree can absorb up to 100 gallons of water and release it into the air, cooling the surrounding area."

And cities around the world are recognizing this cheap and easy way to keep their water clean, and their air cooler.

According to the EPA, the more than half million trees New York City planted in 2007 absorbs more than 890 million gallons of stormwater run-off each year, saving the city more than $35 million a year in treatment costs.

Trees and open space -- like the natural meadow the Pottstown School Board has voted to establish at the former Edgewood Elementary School -- absorb water. It's as simple as that.

But will Pottstown take that step forward, ignore political arguments that have undermined such efforts in the past?

Only time will tell. If experience is any teacher, it may require a big storm for the powers that be to see the light.