Pumping Out Iowa
How cities flood themselves
July 21, 1993
Illinois thunderstorms tend to be brief, local, and violent. They dump a lot of water onto a smallish area faster than sewer pipes can carry it away. Thus has Springfield had a chronic flooding problem even thought it does not sit beside a river.
It’s been wettish lately, and Springfieldians of all classes have been thinking about topics they usually leave to engineers. This of course is part of the problem—leaving things to the engineers, I mean. Modern flood control systems are clever answers to the wrong question—in this case, how to get rid of storm water rather than how to use it.
Cities don’t make floods but they make them worse. The amount of rain and thus the number of what the hydrologists call flood events is dictated by nature, but the severity of floods is increasingly affected by humans having mucked up the watershed. When it rains on the prairies of central Illinois these days, much of the water drops upon hard surfaces—shingled roofs, asphalt roads and parking lots, concrete driveways, mayors’ heads. Thus diverted from the soil, this water moves instead to nearby streams via a network of pipes.
The water that used to dribble into a typical stream course at a thousand points now gushes into it at only a handful. The inundation is swift and violent, as torrents of water slam into streams and rivers whose water-carrying capacity has been artificially reduced. (The diking and draining of floodplains in these parts—and the consequent narrowing of river channels—is done mainly to enable farmers to add to the world’s supplies of surplus grain.) The result? Smaller and smaller rainfalls create bigger and bigger floods, as water that used to diffuse itself over space is now concentrated by humans in time.
One hundred and fifty years ago the progress toward the sea of a hard summer rainfall in Springfield was much more leisurely Raindrops would have been slowed by tree leaves and tall grasses before they fell upon a leaf-littered and untrampled (and thus spongily absorbent) soil surface. Much of the rain would not enter streams directly as runoff from the surface but would seep into the soil where it fell, replenishing groundwater reservoirs. When runoff did overtax a stream’s capacity to carry it away, some of it was simply left behind, as the stream overflowed its unfettered banks onto the aptly named floodplain. From recharging groundwater to nourishing floodplains, stormwater was a resource, a benefit, a boon. Today it is a boon mainly to those who sell sump pumps.
By burying our urban water control systems, we have made their workings invisible and thus unknowable to any but the priests of the engineering cult. A west-sider explained to me that his basement got wet because the ground was by then soaked from repeated rains. This explanation is intuitively true but hydrologically muddled. The seepage of water from the soil through adjacent basement walls causes the chronically damp basement, but a flooded basement is almost always the result of storm water backing up through basement floor drains. During crashing rains like the three-inch-plus downpour that ended July 1, water pours into these pipes faster than it can flow out. For a few hours or so, the storm sewer system is storing water rather than carrying it away. Basements at such times function rather like the floodplain of a natural stream, as a place to dump water that the stream lacks the capacity to move for the moment.
To the extent that flooding is aggravated by too-rapid runoff from an overbuilt city, in short, it maybe said that basements flood because the ground does not get soaked enough. Lawns that slope only a little shed water nearly as fast as pavement, a fact that has led certain ecological restorationists to argue that people ought to have to get a permit to landscape their lots with turf rather than tall grass or shrubs.
Old Springfield straddles the drainages of two of the Sangamon River’s tributary creeks. Rain that falls upon the east side of town generally flows east, toward Sugar Creek (branches of which are still visible near Bergen and Bunn parks). The rest of the city stands on the uplands of Spring Creek. A branch of this stream decorates, indeed created Oak Ridge Cemetery; to the south, the Town Branch of Spring Creek proved so convenient a natural disposal system that the city was tempted to overdo it, so polluting the stream in the last century that it was declared dead and had to be buried inside a pipe.
Pioneer settlers 1ike Zimri Enos recalled that old Springfield had not a pond or a marshy place in it, thanks to this efficient natural stormwater drainage system. Unfortunately, the soils hereabouts hold water rather too well, and the blocking and clogging of these drainage channels turned them into mud so persistent and deep that Springfield’s pretensions as a civilized outpost nearly sank beneath it without a trace.
Today Springfield’s natural drainage system hardly functions at all except at its extremities, where it merely serves as an outlet for the city’s stormwater sewer pipes. The new Springfield being built west of Chatham Road is even less favored by nature. The terrain thereabouts is quite young geologically and has only an immature natural drainage system. Its smooth blanket of glacial debris is as yet unwrinkled by the sort of erosion that cut such picturesque landforms elsewhere in the city. Most of that part of the city is drained by the Jacksonville branch of Spring Creek, a creek-ette that emerges on the old prairie uplands west of Wabash and Veterans Parkway, ambles east more or less parallel with Wabash to Chatham Road, then snakes north through Washington Park (where it has been dammed to make a picturesque pond) before turning northwest.
The State Journal-Register reported that most of the calls to local plumbers to pump out flooded basements came from the south and west parts of town. This is to be expected; more houses in the latter district have basements, and more people have enough money to call in a plumber without cashing in the CDs bought for the kids’ college. The relict natural drainage system has been ditched, straightened, piped, or simply plowed into such deformity along much of its length that it cannot divert, delay, or store enough stormwater from the human drainage system to alleviate basement flooding in heavy rains.
The classic engineering solution is to increase the size of the pipes that we use to move stormwater, or to find things other than pipes to store it in. In Chicago they are digging monstrous holes underground at a cost of billions, and the U.S. Corps of Engineers is complaining that the flooding along the Mississippi is the result of our not letting them have the money to build more water-catching reservoirs on the Mississippi’s tributaries.
If you think pumping out your basement is expensive, wait until you see the bill for pumping out Iowa. ●