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# Surface Water Hidrology - Chapter 2

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### Surface Water Hidrology - Chapter 2

1. 1.  2.11 Frequency Of Point Rainfall 2.12 Maximum Intensity-Duration-Frequency Relationship  Maximum Intensity-Duration Relation  Maximum Depth-Duration Relationship  Maximum Intensity-Duration-Frequency Relationship 2.13 Probable Maximum Precipitation
2. 2. WHAT In hydraulic –engineering applications (e.g flood), is to determine the probability of occurrence of a particular rainfall The rainfall at a place is a random hydrologic process and a sequence of rainfall data at a place; when arranged in chronological order constitute a time series. (Commonly used time series is annual rainfall) This information is obtained by the frequency analysis of the point-rainfall data. Purpose of frequency analysis: to obtain a relationship between the magnitude of the event and its probability of exceedence.
3. 3. HOW The probability analysis can be made by:  Empirical method (e.g. Weibull etc) – Plotting Position  Analytical method (e.g. Gumbel Extreme Value Distribution & Log Pearson Type 3)
4. 4. TERMINOLOGY The recurrence interval (aka return period) is defined as T = 1/P ; where P is the probability of occurrence of an event. Statement: The return period of rainfall of 20mm in 24h is 10years at a certain station A. › Means: an average rainfall magnitudes equal or greater than 20cm in 24h occur once in 10 years. (however, it does not mean that every 10 years one such event is likely to happen) › The probability is 1/T = 1/10 = 0.1
5. 5. SAMPLE QUESTION
6. 6. SAMPLE RESULT
7. 7. SAMPLE GRAPH
8. 8.  2.11 Frequency Of Point Rainfall 2.12 Maximum Intensity-Duration-Frequency Relationship  Maximum Intensity-Duration Relation  Maximum Depth-Duration Relationship  Maximum Intensity-Duration-Frequency Relationship 2.13 Probable Maximum Precipitation
9. 9.  A. Maximum Intensity-Duration Relation B. Maximum Depth-Duration Relationship C. Maximum Intensity-Duration-Frequency Relationship
10. 10. A. MAXIMUM INTENSITY-DURATION RELATION
11. 11. B. MAXIMUM DEPTH-DURATION RELATIONSHIP
12. 12. C. MAXIMUM INTENSITY-DURATION-FREQUENCY RELATIONSHIP
13. 13. SAMPLE QUESTION >> Please Refer Example 2.9 Page 47
14. 14. SAMPLE RESULT
15. 15. SAMPLE RESULT
16. 16. SAMPLE RESULT
17. 17. SAMPLE RESULT
18. 18.  2.11 Frequency Of Point Rainfall 2.12 Maximum Intensity-Duration-Frequency Relationship  Maximum Intensity-Duration Relation  Maximum Depth-Duration Relationship  Maximum Intensity-Duration-Frequency Relationship 2.13 Probable Maximum Precipitation
19. 19. WHAT The greatest or extreme rainfall for a given duration that is physically possible over a station/basin. E.g. from the operational point of view, PMP can be defined as rainfall over a basin which would produce a flood flow with virtually no risk of being exceeded. Done by experienced hydrometeorologist.
20. 20. HOW PMP can be determine using:  Meteorological method  Statistical study of rainfall data; Pm = 42.16D0.475
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