From the AP via CNN:
Anti-flood measures will be reviewed in all Dutch regions below sea level in light of Hurricane Katrina’s aftermath to ensure they would be adequate in an emergency, the government said Sunday. …
The government is planning to spend $3.7 billion over the next ten years on new projects against the threat from river floods, in addition to the $620 million spent annually on maintaining the current system in the country.
Can’t remember where I read this, but one report said that until the mid-20th century, Dutch dikes were built to withstand a 100-year flood. After a serious event, they decided to raise the standard to a 10,000-year flood. I don’t know if that’s even possible to calculate, but it sure sounds good.