EARTHSC 2GG3 Lecture Notes - Natural Disaster, Drainage Basin, Flow Velocity
23 Nov 2013
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Recurrence interval: represents frequency of a natural disaster as an average time between past events, helpful when natural events are random, also called return time. Flood frequency is recorded as recurrence interval: average time between floods of a given size, larger flood discharges on given stream have longer recurrence interval between floods. Calculated recurrence interval depends on: total number of years in flood, record of rank of flood. Any new larger flood reduces rank and thus reduces recurrence interval. For a given-size flood, recurrence interval is: t = (n+1)/m, t = recurrence interval, n = total number of years in record, m = rank of flood (largest flood = 1; second largest flood = 2, etc. ) If the largest flood on a rivet at a single location was in 1997 and there are 87 years of records, what is the recurrence interval for the 1997 flood? m1997 = 1 n = 87.
