Floods -- a man-made disaster

Hurricane Harvey dumped over 50 inches of rain on some areas of Houston, more than they usually get in an entire year.  The Associated Press' Jason Samenow reports that: "This flood event is on an entirely different scale than what we've seen before in the United States."  The Wisconsin Space Science and Engineering Center has determined that it "is a 1-in-1000 year flood event that has overwhelmed an enormous section of Southeast Texas equivalent in size to New Jersey."

Such a wide flooded area has never before happened in the 100+ years that historical records have been kept.   A "1-in-1000 year event" means the chance of happening in any year is 0.1% -- or expected to happen once in a thousand years.  Of course, these estimates are difficult to validate, given the paucity of data at such extremes.

But here is a fact supplied by the authoritative author of "the" book on floods, Michael Grunwald, a guest on "All In With Chris Hayes" on Wednesday.  Grunwald pointed out that, while a "500 year flood event" would be expected once in 500 years, there have in fact been three "500 year flood events" in the Houston area in the last three years.   That's right:   one each in 2015, 2016, and now 2017.

So what's going on here?   Either this predictive scheme is way off -- or something is happening that is changing the weather.   Could that something be climate changes that are caused by the effects of our human activities?

There is near-unanimous agreement among scientists that our climate is being affected by man-made acvtivities and that rainfall has become more intense in recent decades.   That seems well-established, despite right-wing denial.  Grunwald, however, brings up another point that needs to be considered alongside climate change itself.  It also has to do with the effect of human activity.

Grunwald says:  "Storms are natural events, but floods are almost always man-made disasters."   He explains that, when a flood occurs where there is no human habitation, it doesn't matter.   Water overflows river banks, stays a while, and gets reabsorbed into the earth or flows back and moves on downstream.  That's it.

We have trouble when humans cover over large areas of water-absorbing earth with paved parking areas or buildings or shopping centers;   and then they put up structures that obstruct the natural flow of water, like dams, canals, or large drainpipes pouring water into containment areas that can overflow.    Floods cause trouble for humans, because humans have obstructed the natural flow and absorption of excess water.

This becomes especially problematic with growth of large cities, especially in low-lying areas near the coast.   Houston has rapidly grown to be the U.S.'s 4th largest city. It's downtown elevation has traditionally been considered to be 50 feet above sea level, but a recent study of the effects of rising sea level as a result of melting arctic ice, puts the elevation at 42 feet above sea level, with further shrinkage predicted if the sea level continues to rise.   Houston is about 50 miles from the Gulf of Mexico, with other bodies of water and rivers in and around the city.

Another problem discussed by Grunwald is the National Flood Insurance Program, ostensibly an effort to help people get flood insurance, which is required to get a mortgage for building in a 100-year flood zone.   The truth, however, is that despite the requirement, only about 15% of people actually continue the insurance.   The unintended consequence is that this program, meant to help, has in fact subsidized and incentivized living in flood plains, where land is cheaper.  But building there makes flooding more likely.

Back to Grunwald's original point:   the reason these floods are so devastating is that large numbers of people are living in areas likely to flood.   If people didn't build there, a flood would not be such a big deal.

So Houston hits all the wrong buttons:  they have the problem of rapid growth, low-lying and water-adjacent lowlands, near the Gulf coast, the great need for inexpensive housing, lax regulatory enforcement, and a federal assistance program that encourages building in risky places.   So Houston becomes inundated, again and again, by nature being nature -- and by humans being short-sighted.

Add to that the effects of a warming climate due to human activities, which melts arctic ice, raising sea levels, and warmer air meaning air over water becomes even more saturated -- all leads to these 50 inch rains.   Ergo, floods.

We should stop blaming nature . . .  and look in the mirror for the culprit.

Ralph