GEOL 118 Lecture Notes - Lecture 36: National Flood Insurance Program, Federal Emergency Management Agency, 100-Year Flood
10 May 2016
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Geol 118 - lecture 36 - floods ii. Long-range flood prediction = flood frequency analysis. Determine how often you can expect flood of particular size. Uses historic records of flood size (maximum discharge or stage) Plot of discharge (or stage) vs. recurrence interval can be used to extrapolate to different flood sizes. Flood frequency analysis gives values for flood recurrence interval = average number of years between occurrences of certain size flood. N = total number of years of record. M = magnitude (ranking of year under consideration, 1= biggest, n = smallest) Recurrence interval (r) = average number of years between occurrences of certain size flood. Ex: 100 year flood (very large flood that occurs on average once in 100 years. Flood probability (p) = risk (% chance) of certain size flood in any year. Flood probability = reciprocal of recurrence interval. Earthquake risk increases over time as pressure builds.
