主题：【讨论】哪位大侠就三峡问题来个科普系列吧 -- 斯人

A one-hundred-year flood is calculated to be the level of flood water expected to be equaled or exceeded every 100 years on average. The 100-year flood is more accurately referred to as the 1% annual exceedance probability flood, since it is a flood that has a 1% chance of being equaled or exceeded in any single year.[1] Similarly, a flood level expected to be equaled or exceeded every 10 years on average is known as a ten-year flood. Based on the expected flood water level, a predicted area of inundation can be mapped out. This floodplain map figures very importantly in building permits, environmental regulations, and flood insurance.