Saturday, September 15, 2018

Waiting for the creek to rise

Now demolished, the Midtown Sundries building was in a floodplain and flooded regularly. Photo courtesy Charlotte-Mecklenburg Storm Water Services.
Now and then, during extremely heavy rainstorms, my daughter and I used to hop in the car and drive about a quarter-mile away to see if what we call the Creek House was inundated.
The house was built in the 1990s on a you-can’t-believe-it’s-legal site: within about 6 feet from a small creek.

That creek (one of about 3,000 miles of creeks in Mecklenburg County) has the boring official name of Briar Creek Tributary #1 and is neither large nor impressive. Except during a heavy rain. Then it deepens and widens – muddy and dangerously fast-flowing.

At one point, when the Creek House was being built, it was so close to the creek there was a two-by-four propped between an exterior wall and the far side of the creek.

It was a shocking example of how slack Charlotte and Mecklenburg County environmental regulations were, even though they were in some significant ways stricter than the state’s. I sent a copy of the photo to a fellow I knew in the county water quality program; he used it in a slide show urging Charlotte-Mecklenburg elected officials to require undisturbed vegetative buffers beside creeks. I can’t claim that photo is what led the county commissioners to enact the buffer ordinance. But I hope it helped.

Tonight, in Charlotte, N.C., we’re awaiting what may be 10 inches or more of rain from what’s left of Hurricane (now
Tropical Storm) Florence. Flooding is on everyone’s mind. It’s not likely to be as big a disaster as what we are seeing in Eastern North Carolina. But however bad it is here, it’s probably not going to be as bad as it might have been, because of some welcome environmental regulations and government programs.

Floods here tend to be different from those in North Carolina’s flatter, Coastal Plain, or in Houston after last year’s disastrous Hurricane Harvey flooding. Charlotte is a city of ridges, ravines and creeks, and our rainwater and storm drains head straight into the county’s 3,000 miles of creeks and then, usually rapidly, into nearby rivers.

But we’re also a car-oriented city. We have a lot of pavement: streets, highways, surface parking lots as far as the eye can see. It all creates runoff, polluted runoff.

One inch of rain on one acre of impervious surface pavement creates 27,000 gallons of storm water runoff. A few years back I calculated how much runoff one inch of rain on all of Mecklenburg County’s impervious surfaces would create: roughly 2.4 billion gallons. That’s hard to visualize. Think of it this way. If you put 2.4 billion one-gallon milk jugs atop one another, they’d reach to the moon and halfway back.

That's one inch. Not 10 inches. It’s safe to conclude that 10 inches will likely cause flooding in places here that don’t usually flood.

As in many cities, in Charlotte people have built a lot of things in floodplains – like that Creek House – because they’re flat, which makes building easier. Houses, stores, offices and parking lots perch next to creeks throughout the city.

Even with a floodplain ordinance – which the real estate and developer lobby fought bitterly – houses are still built in floodplains. Today, though, they’re perched on piled-up dirt so floodwaters don’t get in but are, instead, displaced and spread farther out, thus causing flooding in places that used not to flood. But whatever.

After some heavy rains and floods in the late 1990s, the county began using federal funds to buy flood-prone properties and demolish them. In some spots greenways and eco-gardens have been created.

Will the buffers, the floodplain ordinance and the eco-gardens reduce the flooding? Will the Creek House, after all, survive another torrent of rain? That’s the hope. But for the results, ask me later, after Florence moves on.

The Chantilly Ecological Sanctuary at Briar Creek, in the Chantilly neighborhood, was once the site of an apartment complex that flooded regularly. Today it's a more natural area, where floodwaters can spread without causing the damages they once did. Photo: Mary Newsom