Posted By Andrew Freiden
You may have seen this story on NBC News last night, which did a great job of explaining how Houston's recent population explosion has exacerbated their flood threat
Here's the piece if you'd like to watch:
But there are other man-made reasons flooding has gotten worse. The first is global warming. As the earth has warmed, heavy precipitation events have increased. The jury is out on if global warming will enhance tropical systems but the science is leaning in that direction.
The reason you might actually not be aware of?
The ground is actually sinking beneath Houston!
The technical term is "Subsidence" and it's caused by a huge drop in groundwater in the aquifers underneath Houston. As we draw down the aquifers and use the water, the land above actually sinks.
Want to read a report about this? Click here for a link to a USGS report on the subject.
Here's a summary:
In the Houston-Galveston region, land subsidence is caused by compaction of fine-grained aquifer sediments (silts and clays) below the land surface due to groundwater withdrawals. Removing water from fine-grained aquifer sediments compresses the aquifer leaving less pore space available to store water resulting in the lowering (sinking or settling) of the land-surface. Most compaction that occurs as a result of groundwater withdrawals is irreversible; even if groundwater levels rise, compacted sediments and the associated land-surface lowering would remain as-is.
Also from the report (Highlighting is mine):
The study shows the ground has sunk around 10 feet in many locations around Houston and Galveston. That's a LOT of sinking. I'm not saying man's impact has caused this horrific flooding in Texas, but our actions in altering the atmosphere and the geography has made Harvey at least marginally worse.
Coastal Virginia is also undergoing sudsidence (but not as rapidly). For us, it's due to global sea-level rise, groundwater extraction, and a rebound DOWN after the last glacial period forced our land UP. It's fascinating stuff, if you ask me.
Read more about it here:
(Thanks to USGS Hydrologist David Nelms for the heads up on this)