Building Drainage Systems for a Changing Climate

New Orleans Pumping Station

New Orleans   On August 5th only weeks ago, New Orleans was caught in a downpour of between 9 and 10 inches in some parts of the city that overwhelmed the sewer and drainage system. The city has been in crisis since that time, as citizens come to grip with what they thought were the strengths of the system versus its real abilities and classic fail. The outgoing mayor’s reputation and legacy, on the rise for his handling of the Civil War monuments, has now drowned since the Sewerage & Water Board was on his watch and under this thumb. The level of contradiction and incompetence revealed in the aftermath of the flooding has left many in the city on edge during hurricane season with the anniversary of the August 29th Katrina hurricane in 2005 only days away.

Remarkably, what was once vaunted as one of the most effective drainage systems in the world, now is a poster child for urban myth. I’m especially sensitive to the mythology here, because I had fallen for it hook, line and sinker as well. After the May floods in the 1980s, I had sucked in a line that the city could handle 3 inches per hour. After the August floods, I had repeated the fiction, and had to retract my line, when the local papers kept reporting that, yes, the system was supposed to be world-class, but that meant it could handle 1 inch the first hour of rain, and clear ½ inch every hour after that. A 10 inch rainfall in their version of the events was a “sky falling” catastrophe that even the best systems could not handle without flooding, especially given the epic level of the rain.

Now with Hurricane Harvey knocking hard at the I-10 Louisiana Welcome Centers across the Sabine River, we read that the Mayor’s office and the local Sewerage & Water Board are having trouble verifying any technical assessment that would have rated the system’s water carrying and clearing capacity even at the level of 1 inch per hour and so forth. This has all of the alarming aspects of an urban myth repeated so often that no once bothered to check the sources until they were finding their life jackets and canoe paddles with the water rising at the front door.

Meanwhile I’m due in Houston this week. Harvey is expected to dump 3 feet of water on Texas. The Houston drainage system is legendary for its limited handling capacity and frequent flooding from homes to interstates on the least heavy rainfall. My friend and comrade sent me a dawn text that they had already had 21 inches hit the city by Sunday morning. He was happy to report the water had covered up his street, but was not up to the porch steps yet. Before you applaud the progress in Houston, the nation’s 4th largest city, you probably need to know my friends live in the Houston Heights, near the apex of the rise. Their story is a high ground story, not one from the lowlands.

But, it’s fair to say that no city, even Houston and New Orleans in the swampy tropics of America, can handle a foot or more of water without some flooding at this point. My question is what are we learning? With climate change we are going to have more of this more often, not less. Are we talking about infrastructure investment and capital programs that will give drainage systems the capacity to handle even a couple of inches of water per hour, much less what we are seeing now with some regularly.

In the classic formulation attributed in the French Revolution to King Louis XIV, “here comes the deluge….” We’re not ready, but can we become able?

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