Tuesday, June 10, 2014

Preventing Floods Without Major Engineering

The photo is the view from my window of yesterday's flood. The thing is, I've been seeing this view more and more often in heavy rainstorms.

Now, I've been living in this house for more than a half century, and I can remember angry torrents running down the gutter, maybe half a car's width wide. I'm near the bottom of the hills of the North End. Every drop of rain that falls on a non-absorbent surface uphill--every roof, road, sidewalk, driveway--makes its way down the streets that lead toward the creeks. One inch of rain on top of the hill adds up to many feet of water at the bottom.

I don't remember runoff ever coming up onto the sidewalk and covering the grass like it does in heavy rain now, becoming a stream that extends halfway across the street--never before, not even in the worst of hurricanes. I remember Sterigere Street through the park being closed many, many times in the past, but Harding Blvd very rarely was submerged. Now, in the heaviest rain, it's almost to be expected.

What's changed in the last 50 years? There's been little new construction uphill. Most of the houses in the North End are at least 80 years old. But more than a handful of those houses have become multi-unit rentals in my lifetime, and households in general now own more cars. Homeowners have paved parts of their back yards for parking spaces. You can't blame them. Parking can be hard to find on the street. Our family did the same, adding two spaces in back. This extra paving creates extra storm water runoff.

Still, I don't think that's the main factor. Much of the North End--and a lot of other areas of Norristown--used to have tree-lined streets. When I was young, our street had 1 or 2 trees in front of each house. Now there's only 4 trees left on my side, and the other side has none. Trees are great for storm water management. Their canopies act like umbrellas, slowing the rainfall, spreading it out. Many species of tree have leaves that actually absorb some rainfall, so less reaches the ground. And of course their roots act like sponges--those with surface roots can be especially good at absorbing rainfall because they don't have to wait for the water to soak into the ground. Thing is, the ones with surface roots, like the big sycamore in the photo, tend to be the ones we cut down first, as their roots push up our sidewalks.

Another trend I've noticed is the tendency for new homeowners to rip out established gardens in favor of grass. This has happened all around my neighborhood, especially when the houses are bought as investment properties. The landlord doesn't want to deal with maintaining a garden--just wants to mow a lawn--so all the shrubs and perennials are removed. A healthy lawn may be good for preventing erosion (the grass underwater in the photo bounced back this morning looking as if nothing had happened), but grass isn't as good at absorbing water as trees and shrubs. And, as you can tell by the color of the water in the photo, the greater and faster the runoff, the more erosion you'll have, too.

Consider the way the Markley Street improvements are paving the areas that used to be the grass strips along that road. PennDOT removed all those big sycamores along Roosevelt. Even if they improve the storm drains, well, that water has to go somewhere eventually--into Stony Creek and the Schuylkill, to create floods downstream.

As I think I mentioned in a prior Diary entry, the overflow hose from my rain barrel waters my side garden. I have 2 trees there--a Japanese maple and a redbud--plus a few azaleas, hostas, ferns and other perennials. The trees absorb an amazing amount of water during storms, every drop that falls on the back half of my house, which yesterday was at least 200 gallons.

If homeowners in Norristown planted one tree or bush, if commercial property owners could line their parking lots with trees and bushes, if vacant lot owners could be made to plant something besides grass, and if our municipal government would do the same on their properties, all this would go a long way toward solving our increasing storm water runoff problems.

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