Friday, May 27, 2011
Rain. We have rain. We've had rain. We've had rain all month. We've had rain all spring. We've had rain since late winter. I think I could use up fingers counting the days without rain and still have enough left over to plink out Chopin's "Raindrop" Prelude.1
So far this month Ann Arbor has received over 6" of rain, which is twice the 3" average for May, and it's expected that we'll add to that throughout the weekend2. For April, it was 5.5" and for both March and February it was somewhere around 4" (including snow). This past Wednesday, it was 2.2" in one day. That's a lot of water, far above the monthly average for at least four straight months now.
Fortunately, Michigan drains to both west and east. That means neither the Grand River draining into Lake Michigan, nor the Huron River flowing through Ann Arbor toward Lake Huron, has to contain the full collection of rainfall in the way that the Mississippi River does. Here's a map of the Mississippi drainage. Just look at that! Half the country's waters drain through New Orleans! No wonder the lower Mississippi is so vulnerable to flooding -- they have to receive everyone else's water, not just their own.
So for all the rain we've had in Michigan, flooding has occurred only sporadically. Michigan sheds its excess water quite easily and has enormous basins on either side to catch the runoff. Lucky us.
So far, I've seen no rainbows in the sky, but I don't worry too much about the entire world flooding.3 For that, I have something better than a rainbow: a basic understanding of how the world works and some basic arithmetic. For example, Michigan averages 35 inches of rain per year. But to flood the earth enough to cover the mountains with just 40 days of rain? Let's use that arithmetic: Mount Everest is 29,035' above sea level and there are 960 hours in 40 days and nights. That requires a rate of flooding of 30 feet per hour! Ten times as much water, in a single hour, as a Midwestern state receives in an entire year! That's ... well, incredible. As in "not credible," not to be believed
Where would so much water come from? The ancients of the Near East seem to have imagined that the sky was a solid shell and that the "waters of the deep" surrounded both earth and sky in all directions; when Genesis 1:6 has God declare, "Let there be a firmament in the midst of the waters, and let it divide the waters from the waters," that should be understood as a division in three dimensions, not just two. There was water below the earth and above the sky, so in order to flood the earth, "the same day were all the fountains of the great deep broken up, and the windows of heaven were opened." [Genesis 7:11] For those forty days and nights, the waters were no longer divided from the waters. It wasn't just raining. The earth was simultaneously foundering and receiving an infinite ocean pouring through those windows in the sky. Under that kind of assault, an ark might have to be as watertight as a submarine to avoid flooding itself!
Fortunately, we have a more accurate cosmology today and we know that such quantities of water just don't exist anywhere within reach. The moisture in the ocean, lakes, rivers, and clouds is all there is on earth and if there were enough to cover the entire planet, it would do it every day. That doesn't save us from floods altogether, alas; it just means that floods are very local affairs. Some are big enough to feel like the end of the world, if you were to experience them, such as the Glacial Lake Missoula floods I mentioned last autumn. William Ryan and Walter Pittman have even suggested a breakthrough of the Mediterranean into the Black Sea as the origin of the Flood mythology. But that's a local catastrophe nonetheless; if you have too much water, that just means that somewhere else has less than it did before. Now doesn't that make you feel better?
1. Not Chopin's name for opus 28, no. 15, just so you know.
2. The forecast looks a little better for the race in Indianapolis Sunday, but it's likely to be hot and breezy, which should make life exciting for the engineers. I won't be surprised if some good drivers struggle with unexpectedly slow cars when the race gets under way.
3. We just escaped yet another prediction of the end of the world, so I'm just wallowing in complacency these days.