ESS124
Prof.
Jin-Yi Yu
Magnitude of Flood
•Hydrologists often use terms
like “100-year flood” or “500-year flood”
to convey the idea of a flood’s magnitude.
•These numbers are developed
by extrapolating historical data to longer
time periods.
•The term “100-year flood”
means that, in any given year. There is
a one in 100 chance of a flood of that particular magnitude.
•In other words, the
probability of a flood of that particular magnitude in any given year is 1/100 or 1 percent.
•The actual amount of water
that causes a particular flood (e.g., a 100-year flood) varies from river to river.