They might mistakenly gamble that similar flooding won't return for 99 years. The 100-year flood standard was originally developed only for use in floodplain mapping, according to Carl Cook, deputy federal coordinating officer for mitigation. There is no magic reason to attempt to relate every flood that occurs to the standard used for mapping. In fact, most recent flooding has been well below the 100-year level. And of course, flooding is always a serious disaster for the families affected.
Mitigation involves taking steps to reduce the amount of damage from rising water.
That can range from elevating key appliances in a home, to elevating the entire residence. Local building departments or emergency management offices can provide information on steps to be taken.