Two Fun Facts

Here's a fun fact for you:  If you live in New Orleans, you're under water.  Like, right now, there is water higher than your front door.  This panoramic picture is from the Mississippi River Levee less than a mile upriver from my house, taken just a few days ago.  Even though this is some of the highest ground in the city, you can see that the river level is higher than the houses on the road behind the levee.  If the levee weren't there, we'd all be wet.

That street you see (the street the houses are on, not the path on top of the levee) is at about 7 feet above sea level.  Below is the record of the water level in the Mississippi River in New Orleans since October.  You can see that the river has been up above 7 feet since early March, and looks to remain up there for a while longer, so the people in those houses have been looking up at the bottoms of boats for months.

I think that there are two possible reactions that you could have here.  On the one hand you could nod sagely, stroke your chin, and declare with authority that "nature will always have her way" or some such.  And then go buy a snorkel.  Or you could recognize that this happens pretty much every year during the Spring flood.  If you're in New Orleans from March to May there's an excellent chance that you're under water, and it simply isn't a problem.  Every year the river rises above Southeast Louisiana, and ever year people go about their business with little or no interruption because the river levees are so reliable.

The lesson I like to take from all this is that, while doing so is no small task, it's perfectly possible to wall off water.  We do it every year, and the flood protection system along the river is sound enough that everybody in the city can simply go about their business without any special arrangements.  And if it's perfectly possible to wall off water from the river then shouldn't it also perfectly possible to wall off water from the sea?  In fact it is.  Which means that the even more important message here is that there's no inherent contradiction in having a sustainable city that's beneath sea level, which parts of New Orleans certainly are.

So next  time you hear some dimwitted congressperson telling you that no manmade structure can possibly hold back the ocean you should feel free to ignore her.  And, while we're at it, here's another fun fact before I go: I live in the Lower Ninth Ward and I'm on some of the highest ground in the city.  Did you know that those both could be true?

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*For the curious, I said that the street in the picture is 7 feet above sea level, but what I really meant was that the street is at 7 feet of elevation relative to the North American Vertical Datum of 1988, or NAVD88.  The datum is essentially an agreed upon "zero" level, which is important when you realize that the sea goes up and down all the time.  The river stage is referenced to that same datum, which, in South Louisiana, is a pretty close approximation to the mean sea level.  Strangely that's not true everywhere;  measuring sea level is much more complicated than you might expect.