In The Flood Zone

Simone Foxman wonders why "the government won’t pay for flood prevention, but it will pay for flood damage that the prevention might have prevented":

The US … is fixated on rebuilding flood-damaged homes rather than preventing future damage. As it stands, “repetitive-loss properties,” defined as those that have suffered damage up to 25% of their total value twice in 10 years, “account for just 1 percent of [National Flood Insurance Program's] insured properties but are responsible for 25 percent to 30 percent of claims,” according to a report published (pdf) by the Government Accountability Office (GAO) in 2011. The bulk of those properties are located along the Gulf Coast (which has the highest number of claims), and subsidized by properties up north (where there is high coverage but a low volume of claims).

In response to a report detailing which artifacts in the still-unfinished 9/11 museum are likely damaged, Taylor Berman asks:

It seems worth noting here that the memorial cost at least $700 million to build; perhaps some of that could have gone to more comprehensive flood prevention?

From the report:

It was understood that a portion of the memorial was to be constructed in a 100-year flood plain — that is, an area of dry land with a 1 percent chance of flooding each year due to storms (and, therefore, a 100 percent chance of being flooded once a century). … It did not seem conceivable then that a 100-year flood would occur during Hurricane Irene last year — before the museum’s opening day — and that a second disruptive storm would pass through 14 months later.

Update from a reader:

Not true. Something with a 1% chance per year for 100 years will happen with a probability of 63.4%. (The equation is 1.0 – 0.99 ^ 100)