NRG from above
In a few hours, the eyes of much of the United States, and a nontrivial part of the world, will focus on the stadium that appears open at the top in this view. What is today NRG stadium sits next to the classic Astrodome, both sitting in the center of Houston, Texas.
It is disturbingly difficult to find details of the ground that sits beneath the buildings of Houston. The land itself is, honestly, somewhat bland. It is perhaps the flattest land you’ll ever see; the city’s skyscrapers are viewable from tens of kilometers around due to the gentle slope of the land. But, if you were to search for “Geology” and “Houston”, you’ll find nothing but a list of available jobs in the oil and gas industries. Home to the headquarters of such behemoths as Shell, Schlumberger, Exxon, Houston Texas is the center of employment for the oil and gas industries in the United States, and scientists based in Houston travel around the entire world to survey the geology of more interesting or profitable sites.
Houston sits on the Texas Coastal Plain, what would, if geoscientists really looked at it, be a complicated set of river deltas and coastal plain sediments deposited over millions of years. About a dozen major river systems cross this land today, migrating from side to side as rivers regularly do. These systems carry sediments eroded upstream, including from the highlands of Central and Western Texas.
During the Triassic and Jurassic, the Gulf of Mexico began forming as Pangaea rifted apart. Much of the Gulf coast is underlain by a thick deposit of salt called the Louann salt (https://tmblr.co/Zyv2Js2AOWwNO) deposited in shallow seas as the supercontinent broke apart. From there, river systems deposited sediments that have built gradually outwards, depositing one layer after another and building the continent outward into the ocean basin. Several fault systems and aquifers sit buried beneath the coastal plain, creating complexity at depth.
The year 2016 featured a historic series of floods hitting the rivers that flow through and around Houston. Rainfall events are calibrated statistically – when rainfall volumes are recorded over years and decades, that allows projection of how often extremely large rain events happen (https://tmblr.co/Zyv2Js1vfiXni). In 2016, two different “100 year storms” hit in the space of a week, triggering huge flooding in April. This was only one in a series of major floods in recent years, weirdly following major drought that hit Texas a few years beforehand. These extremes – major droughts followed by major floods – are consistent with the patterns expected with climate change, where increasingly severe weather events are triggered by the extra energy in the atmosphere.
In 2008, Houston was ravaged by hurricane Ike. The city mostly evacuated beforehand, but the damage and flooding were severe. Houston sits at the tip of a major estuary, an open bay facing the ocean surrounded by Barrier Islands. One of these barrier islands is Galveston Island, which was devastated by a Hurricane in the year 1900. When hurricanes hit at the appropriate spot – basically hitting Galveston Island, the strongest storm surge will be focused into Galveston Bay, just north of that Barrier Island. Galveston Bay leads into other harbors near the city of Houston itself and it is heavily industrialized, with shipping ports for industrial products and major fossil fuel refineries.
Hurricane Ike only brushed this area. A direct impact of an intense Gulf Hurricane could seriously damage these industrial sites, triggering large releases of pollution and knocking billions of dollars of industry offline. On top of that, a series of stored barrels containing dioxin sit on the edge of Galveston bay, contained for now but potentially disturbable by major storms.
Since 2008, Houston has been considering building major flood control systems comparable to those found in Europe today, but no single plan has been agreed on. The most commonly cited plan, known as the “Ike Dike”, involves extending a seawall on Galveston Island to cover much of the bay, Different version of the plan continue to be developed, some of which would extend across much of the bay. Although these plans are available on the books, money has yet to be appropriated to even begin construction, so if Houston were to be hit by a storm more intense than Ike the city would be sitting there with developed plans and little to show for them.
Sunday’s forecast calls for a cloudy day with possibly light rain. The stadium in Houston, now named for NRG energy, has an opening roof, but it is thought that today it might have to stay closed as part of Lady Ga-ga’s performance. We’ll see.
-JBB
Image credit: NASA http://earthobservatory.nasa.gov/IOTD/view.php?id=46945
References: http://bit.ly/2jQ4DL8 http://bit.ly/2kFN2JZ https://pubs.usgs.gov/of/1994/0461/report.pdf http://www.nhnct.org/geology/geo2.html http://www.lib.utexas.edu/geo/balcones_escarpment/pages35-40.html http://bit.ly/2kulMvH http://slate.me/1Zks6D4 http://bit.ly/1GN06ld