Flood Prediction
A flood-ravaged road, once traveled by visitors to Coralville Lake, ends abruptly in a series of bedrock ledges that take visitors on an unexpected journey into Iowa's geologic past
(U.S.G.S.).
In the table that follows the N Maximum Annual Discharge data are ranked with the largest discharge having rank M = 1 and the smallest rank M =15 (in this case).
The Recurrence Interval (RI) is the average interval, in years, between occurrences of two discharges of equal (or greater) magnitude. This
relationship, known as the Weibull equation, can be written:
where N and M are defined as above.
The Annual Exceedence Probability (P) is the probability (expressed as a percentage) that a flood of that magnitude or greater will occur in a given year and is given by:
Maximum Annual Discharge Along The Diamond River, Wentworth, New Hampshire
| Year | Maximum Annual
Discharge (cfs) | Rank | Recurrence Internal | Exceedence Probability |
|---|
| 1982 | 4,600 | 11 | 1.45 | 68.75% |
| 1983 | 6,500 | 5 | 3.20 | 31.25% |
| 1984 | 8300 | 2 | 8.00 | 12.5% |
| 1985 | 7250 | 4 | 4.00 | 25.00% |
| 1986 | 6,000 | 6 | 2.67 | 37.50% |
| 1987 | 5,200 | 8 | 2.00 | 50.00% |
| 1988 | 8,000 | 3 | 5.33 | 18.75% |
| 1989 | 4,500 | 12 | 1.33 | 75.00% |
| 1990 | 5,000 | 9 | 1.78 | 56.25% |
| 1991 | 4,200 | 13 | 1.23 | 81.25% |
| 1992 | 9,400 | 1 | 16.00 | 6.25% |
| 1993 | 3,600 | 15 | 1.07 | 93.75% |
| 1994 | 5,800 | 7 | 2.29 | 43.75% |
| 1995 | 4,000 | 14 | 1.14 | 87.50% |
| 1996 | 4,700 | 10 | 1.60 | 62.50% |
Click on the answer bar to see the choices.
Last Four Digits of SSN :
- The Recurrence Interval for the largest event out of 100 events is 100.
- About every six years there will be a flood with a discharge of 9,400 cfs.
- The probability of occurance of an event with a discharge of 5,200 cfs is 50%
- The average interval in years for an event with a discharge of 5,200 cfs or greater is 2 years
- An event has a Recurrence Interval of 3. This means that there is an average interval of 33.3 years between events of this (or greater) magnitude.
- About every eight years there will be a flood with a discharge of 8,300 cfs or greater.
- A 100-Year flood occurs in 2000. There will be no flood of equal or greater magnitude until 2100
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