August 31, 2011

HURRICANE IRENE: “It makes you think a lot about physics.” “It’s just water, earth, and gravity … a combination of an astonishing amount of rain, steeply sloped hillsides, and ground that was more-or-less completely saturated even before the storm hit. To give you an idea of how much water we’re talking about, take another look at that video of the stream behind our house. This little brook — much too small to even have a name — would, ordinarily, in late August, have a trickle of water in it, at most. The watershed that feeds it covers an area of around 5 square miles — one of thousands of such little watersheds feeding into little streams in southern Vermont (all of which feed larger streams, which feed larger streams, etc.). Five square miles is about 22 billion square inches. Eight inches of rain (which is about what we got) falling on that one little watershed makes for around 175 billion cubic inches (around 100 million cubic feet) of water. All of that water has to make its way behind our house.”