2.  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

3. 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.

4. 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)

5. 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

6. SAMPLE QUESTION

7. SAMPLE RESULT

8. SAMPLE GRAPH

9.  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

10.  A. Maximum Intensity-Duration Relation
 B. Maximum Depth-Duration Relationship
 C. Maximum Intensity-Duration-Frequency
Relationship

11. A. MAXIMUM INTENSITY-DURATION RELATION

12. B. MAXIMUM DEPTH-DURATION RELATIONSHIP

13. C. MAXIMUM INTENSITY-DURATION-FREQUENCY
RELATIONSHIP

14. SAMPLE QUESTION
>> Please Refer Example 2.9 Page 47

15. SAMPLE RESULT

16. SAMPLE RESULT

17. SAMPLE RESULT

18. SAMPLE RESULT

19.  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

20. 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.

21. HOW
 PMP can be determine using:
 Meteorological method
 Statistical study of rainfall data; Pm = 42.16D0.475