THE FLOOD PLAIN LADY
Two re-blogs from prairiemary.blogspot.com.
Friday, June 20, 2008
For a few years in the Nineties I was the “flood plain lady” for the City of Portland. That is, I was the clerical specialist for the Site Development team, who had custody of the flood plain maps, and when someone called up to find out whether a property were in the flood plain, I was the one who was supposed to tell them. The maps were huge and there were a lot of them. I’d unroll them on the counter and try to figure them out. They were out of date. The flood plain was a legal category built on engineering estimates of a changing terrain and weather pattern. The public never understood that: to them it was simply whether the place would flood. Would it flood every fifty years? Every hundred years? Every five hundred years?
Hell, who cared? They just wanted to build what they wanted to build and they saw all this land sitting there with nothing built on it. Seemed perfect. Nice and cool. Fairly flat. Good view of the river… They asked their neighbor who had lived there ten-twenty years and the neighbor said it had never flooded before.
There is so much pressure from the public that the politicoes force the plans examiners to let people built on the flood plain if they build “flood resistant” buildings. (There’s no such thing as a flood-proof building.) Mostly they required high foundations, so the sills of the house were above the height the water was likely to reach. Foundations with holes in them, so that water would flow through. (Waterborne gas tanks, sheds, vehicles and trailer homes would NOT flow through.) If water comes up one-third of the way on a structure, it will float — then turn over — unless it’s attached to the foundation with steel straps.
One woman formerly from the Soviet Union came back with new plans every week. The last one showed foundations thirty feet high with a little one-story house perched on top. She knew from her experience in the homeland that if she nagged long enough, the authorities would shrug and say: “Aw, let her build. If she loses everything in the next flood, she asked for it.” But we held fast. She had no clout.
The point of quantifying flood damage and likelihood was actuarial because the US insures people devastated in floods. I remember as a small child watching the newsreel footage of houses floating with people in the roof, sometimes clutching their dog. The whole Missouri/Mississippi complex evolved as drainage for the North American continent on the east side of the Rockies when the glaciers finally melted ten thousands years ago. In the Thirties the engineers thought they had tamed the rivers, and they had certainly spent a lot of money.
When engineers go after a problem, they try to quantify and calibrate and invent classifications for sorting. So they got out all the rainfall measurements (since the 1800’s when there were white people around to keep records) and then they figured out how much water must have been rolling down the rivers. Then they got out their contour maps — the ones with all the little lines that show elevation by getting closer and closer together as the rise gets steeper — and tried to calculate the carrying capacity of the flood plains. They chose one of those elevation lines to be the isobath, the height they figured the water would reach. Of course, those lines greatly simplified the terrain and they were drawn quite a while ago. Land doesn’t just sit there: people fill in with more dirt, banks erode.
The Flood of the Century in the Red River country in 1997 — which was a few feet deep and miles wide — was complicated because the Red River flows towards the north, so it melts from the south while the water is still frozen farther north, creating dams that raise the water level. The floods came so often in Winnipeg that people finally consented to create diversion canals — they were barely adequate. Grand Forks failed to take any precautions so that the water came deep and hard. When a fire started, no one could get to it so it took out eleven buildings and sixty apartment units.
The flood about the same time in the city of Portland had nothing to do with ice: it was about heavy simultaneous rain in BOTH the drainage of the Columbia and the drainage of the Willamette so that they met at the city. Such a chance event, unpredictable as are many things when it comes to weather, was so unusual that the people — many of whom moved there because the city was “pretty” and “civilized” — had insisted that the top of the downtown flood wall be removed so they could see the nice view. (Historically, Portland has always been vulnerable to floods.) Luckily, there was a lot of new home construction and when the mayor put out a call for help, crews came from all over town with plywood, plastic sheeting and their hammers to save the downtown. It barely worked.
The levees that were supposed to be saving the airport from a repeat of the Vanport Flood had been breached by muskrats and nutria, burrowing in and out, and were bubbling up water from the ground on the “safe” side of the levees. At the airport the big planes that couldn’t be flown out quickly were towed up to a highway — quite a sight. Shopping malls and manufacturing businesses had built where Vanport used to be. The mayor had to decide whether to evacuate them or not. She decided not, on grounds that lives might be lost through the chaos of evacuation and the city would be liable. Of course, if Hayden Island had flooded again, lives would also likely be lost. Luckily, she won her gamble, but it could have gone the other way.
Not long afterwards someone suggested that a much-needed county jail be situated on that flood plain. The head of Site Development, a quiet but stubbornly intelligent man, went to a hearing to tell them how likely it was that such a jail would be flooded and that rising water might lock all the fancy electronic doors so that no one could escape. Another person at the hearing sneered, “Who cares? Good riddance!” Our hero, our boss, pointed out that his own brother was a guard at a Portland jail and did not by any measure deserve to die. If anyone does.
It’s hard to educate people who don’t want to know. It’s hard to commit massive and expensive relief efforts to people who have been warned and warned and restricted and guided over and over and over again. But we are being taught hard lessons in the wettest of ways. The bottom line is that the earth does not care. Romanticize all you want. Floods, hurricanes, earthquakes, erosion, rainfall patterns — no engineer can do much more than run along behind taking notes.
But people got so angry that when I was the flood plain lady, I kept a can of bear spray under the counter. If I’d had to use it, of course, the building would have had to be evacuated.
Thursday, June 09, 2011
The first time I drove to Great Falls after moving back to Valier in 1999 and got close to town on highway 89, I gaped and gasped. Suddenly, with my City of Portland “flood plain lady” eyes, I saw nothing but potential disaster. Now it’s here. There were dikes and levees, there were some houses that were plainly built to some kind of flood plain standards (high foundations, bedrooms on the bottom floor with easy egress, etc) but like so many settlements, Great Falls is built on the confluence of rivers because those were the first highways and because settlements need water. Also, rather uniquely for this state, the actual Great Falls were and are a major source of hydroelectric power, enough for metal refining.
But the pressure to build and the low prices that go with previously flooded places like Sun River combine to encourage outlaw housing. Some people have the idea if they get established there, the government will be obligated to maintain levees and supply insurance. But not this government, not now.
The journalists are pointing out over and over and again and again that no one properly understands the rule-of-thumb about flooding, which does NOT mean that in a “hundred-year” flood plain there will only be one flood every century. It means that every year there is a one per cent chance of flooding. In fact, since weather patterns tend to persist for a few years (even this year’s rogue pattern is not that different from last spring) there tend to be clusters for a few years.
Anyway, what the engineers did in hopes of getting some kind of provisional order was to guesstimate the volume of water likely to travel through a flood plain, use the isometric height contour maps to get a kind of estimated boundary, and then draw an imaginary line. It’s all “if-then” thinking and since people are constantly filling in and leveling the land, the surveyed contour maps are soon out-dated. In the Nineties the Portland Site Development team was constantly having to make decisions with major financial consequences for builders according to maps that were largely fantasy.
Now, of course, with GPS and satellite imagery, things are slightly better, but the whole concept needs to be rethought because of Global Warming. Global Warming does NOT mean that the planet will soon be toastier (though that, too) but more relevantly means that the dynamics of weather will be radically changed because they will be driven faster and harder by the increased energy we call “warmer.”
I read stacks of information on what happens to houses in floods. First of all, they float off their foundations, since they are built like upside-down boats. In some places the house sills may be bolted to the foundation and that’s a good thing (for earthquakes, too). When a floating house is surrounded by water up to a height of about a third, it is likely to turn turtle, though it might not go all the way over and end up on its side.
But the real danger is from floating debris crashing into the house, whether or not it is waterborne. Other houses, big trees, and things like propane tanks that might explode, or cars which float as well as houses. Then, of course, the infrastructure of piping and wiring throughout a town is likely to be damaged with bad consequences. We’re sweating our sewer system at the moment, including the settling lagoon. I’ve got a sump pump running in the basement and am badly in need of enough of a rain break to repair my gutters. Valier is built on gumbo, ancient volcanic dust, which when dry is like cement with big cracks from shrinkage but when wet turns to sticky pudding and will not support weight. The water is not coming in through cracks in the foundation, but welling up at the bottom from the saturated water table.
Yesterday I zoomed north to Shelby to pick up some supplies and also out of curiosity to see the Marias River, which comes out of some of the highest snowpack in the Rockies. Sure enough, it’s way out of its banks and carrying debris, like trees, from banks that have caved. I didn’t expect caving at the cut-down of the exit to the town, but crews were trying to figure out what to do. The sliding dirt wasn’t falling on the road yet. In Billings, the badlands rimrocks that rise above residential neighborhoods are loosing boulders big enough to crush houses. A house there just exploded from accumulated natural gas, probably released by shifting pipes.
Infrastructure includes vital transportation. Water is taking out roads, large and small, and bridges, of course, but I did not know that it could warp and shift railroad track. Though farmers are always begging for water in this dry country, the timing is lousy. No one can get a wheeled vehicle into the field to plant and what was planted before the deluge is now rotting and floating. No sunshine to drive roots into the ground and call out foliage.
This was supposed to be another high-productivity year for Montana, much needed because other areas around the planet are having atypical weather patterns that have diminished their crop yields. The planet’s reserve is drawn down, more than it would have been if so many grains weren’t grown now to produce ethanol. Everything is connected.
FEMA is maxing out. People have figured out how to game the system, and maybe the worst consequence of that is those who legitimately need help get short-sheeted. Montana’s Governor Schweitzer has advised towns not to depend on the National Guard, which will be busy doing other things than sandbagging, like rescues and preventing looting.
Maybe all those people who want to build houses on beaches will think again, as will those who want to build in scenic but combustible forests. In many cases we are living in exciting places with as much expensive technological and fuel support as we would need in outer space. Air conditioning is all that keeps trailers in the SW from baking their occupants to death. Moving one’s house (an RV) to fit the weather is a good (old) idea except for the cost of the fuel. It worked better with horses.
In this rural community we cope pretty well. Infrastructure isn’t that dependable even in the best of times. So we depend on common sense, ingenuity and community memory. For many of us, that goes back to 1964 which was NOT a hundred years ago. I’m intrigued with the idea that this is related to sunspot activity, which is increasing greatly. Floods may be nothing compared to the loss of our satellites. The planet IS a space ship. Sometimes flying blind.
