The fundamental takeaway from this article is about half way down. Major flood events are occurint more frequently. What was once likely to hit a city every 500 years is happening to more cities on a planetary scale more frequently.
The actual takeaway is that our data is wrong, these floods occur more often than we thought. With only 150 years of good data, it's impossible to calculate "500 year" events accurately. You would need around 5,000 years of data to do that, and we don't have it.
So we ended up significantly underestimating how often these events occur.
https://en.wikipedia.org/wiki/Geography_of_Houston
Would love to ask these gentlefolks that question: http://www.beg.utexas.edu/presentations/2005_presentations/b...