A 100-year flood has a 1% chance of happening in any given year. A 500-year flood? Just a 0.2% chance. But that doesn’t mean ...

With the frequency of catastrophic flooding, one civil engineer says we need to change the definition of 100-year floods, and he says local and state government policies can play a role in preventing ...

Weather forecasters sometimes warn of storms that unleash rains so unusual they are described as 100-year or even 500-year floods.