Notes on the 100 “year” flood

Here’s the Lead: Stop with the word “year.” Remove it. The word doesn’t mean what you think it means. So, stop it!

So I just wanted to share a few thoughts.

First and foremost, many recent reporting about the Texas flooding are spot-on. This was/is a disaster due to climate change. In addition, the current attitude, policies, and political will of this Administration and across many states such as TX has been to actively ignore our weather’s increasing risks -our threats, vulnerabilities and consequences. In addition to the public sentiment that is aping those conservatives in power, there is also a limited level of understanding of one’s risks – be it weather-related or human caused.

Especially when it comes to something like floods, which is the Nation’s most frequent, costly and deadly hazard. On top of that, this lack of understanding is compounded by officials and their technical experts’ inability to communicate these issues in a simple and effective way.  Everyone up and down the communications chain – political officials, state and local department heads, academics, technical engineers and architects, the news reporters, and the members of the public they interview at the disaster site – will say 

• “100 year flood” or
• “I’ve lived here XX years, and I’ve never seen this bad,” or
• “flood of the Century”

But especially “100 YEAR flood”   

This term-of-art has been the shorthand civil engineers since the 1960’s since HEW (–Department of Health, Education and Welfare) funded a commission to explore a federal flood insurance program (one of the last “Great Society” programs to be launched). To this day, everyone with a role in flood management will use the term “100 year flood”.

However, the term “100 year flood” is shorthand for the

• 1 percent (1 in 100) annual chance of water exceeding a given geophysical location.

This is a probability! It is not an event scale. It is NOT a flood of the century.  Or any century. Its more akin to gambling. Its a bettor’s risk calculations. Think of it as: Me, holding a 100-sided dice with “1” on one face, and “0” on the other 99 faces; and I’m rolling that die over, and over, and over…

This 1 percent (1 in 100) annual chance is the probability calculations that engineers did across millions of miles of coasts, rivers and streams –first with slide rules, then advanced computing power—based on historical data on the given area’s Topography, Hydrology, and Hydraulics.

And the kicker is that this 1 in 100 annual probability can happen 2 to 3 time during a 30-year period.  I didn’t initially know that, full disclosure. Most don’t. I did not until I dove into this topic. When I tell someone almost everyone questions where I got that from. Hey, its maths, which way beyond my skills, so I just trust the experts.

Here’s another kicker: according to FEMA’s data on flood-related disasters, on average, about 30 percent of damage that occurs from flooding is outside the designated hazard zones on the flood insurance maps.

Looking back to the inception of this program, the 1 percent (1 in 100) annual chance was recommended by a congressional commission of civil engineers, and then written into the National Flood Insurance Program Act of 1968, because it was their best representation of flood risk at that time and given all the data.

In addition, it was also a percentage whereby the NFIP would be revenue neutral and not create large fund balances over time. The ‘1 percent’ was a break-even data point for a federal government program that was/is providing a common good. Which generally worked. The program ran either a fund balance in one year, which paid for another year’s deficit, or Congress would square FEMA’s accounts if the deficits were occurring for multiple years in a row. This status quo lasted until around 2005, and Hurricane Katrina. Or: That is until Climate Change which now renders historical data as irrelevant. Or: All bets are now Off.

In my UDC class I have stated to refer to “Climate Change” not just as “human-caused Climate Change” but as “capitalism-caused Climate Change”.  Because for me, its not enough to point out that human activity has generated all this additional CO-2 in the air.  It is the main feature of our western, capitalist, fossil-fueled industrial, transportation and energy-based economy. Alternatively, for example, consider the world’s indigenous populations such as Native American/1st Nation. Indigenous populations around the world all espouse a communal, steward-of-the-land, political and religious lifestyle.  How much greenhouse gases do you think native tribes generate, versus greater LA on your average Tuesday? [Extra credit for anyone who can quantify the above comparison.]