surface water hidrology - chapter 2
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KKKA 6923 Surface Water Hydrology
KKKA 6923Surface Water Hydrology
Muhammad bin RamlanP57600
KKKA 6923 Surface Water Hydrology
CONTENT
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
KKKA 6923 Surface Water Hydrology
2.11 Frequency Of Point Rainfall
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.
KKKA 6923 Surface Water Hydrology
2.11 Frequency Of Point Rainfall
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)
KKKA 6923 Surface Water Hydrology
2.11 Frequency Of Point Rainfall
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
KKKA 6923 Surface Water Hydrology
2.11 Frequency Of Point Rainfall
SAMPLE QUESTION
KKKA 6923 Surface Water Hydrology
2.11 Frequency Of Point Rainfall
SAMPLE RESULT
KKKA 6923 Surface Water Hydrology
2.11 Frequency Of Point Rainfall
SAMPLE GRAPH
KKKA 6923 Surface Water Hydrology
CONTENT
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
KKKA 6923 Surface Water Hydrology
2.12 Maximum Intensity-Duration-Frequency Relationship
A. Maximum Intensity-Duration Relation B. Maximum Depth-Duration Relationship C. Maximum Intensity-Duration-Frequency
Relationship
KKKA 6923 Surface Water Hydrology
2.12 Maximum Intensity-Duration-Frequency Relationship
A. MAXIMUM INTENSITY-DURATION RELATION
KKKA 6923 Surface Water Hydrology
2.12 Maximum Intensity-Duration-Frequency Relationship
B. MAXIMUM DEPTH-DURATION RELATIONSHIP
KKKA 6923 Surface Water Hydrology
2.12 Maximum Intensity-Duration-Frequency Relationship
C. MAXIMUM INTENSITY-DURATION-FREQUENCY RELATIONSHIP
KKKA 6923 Surface Water Hydrology
2.12 Maximum Intensity-Duration-Frequency Relationship
SAMPLE QUESTION
>> Please Refer Example 2.9 Page 47
KKKA 6923 Surface Water Hydrology
2.12 Maximum Intensity-Duration-Frequency Relationship
SAMPLE RESULT
KKKA 6923 Surface Water Hydrology
2.12 Maximum Intensity-Duration-Frequency Relationship
SAMPLE RESULT
KKKA 6923 Surface Water Hydrology
2.12 Maximum Intensity-Duration-Frequency Relationship
SAMPLE RESULT
KKKA 6923 Surface Water Hydrology
2.12 Maximum Intensity-Duration-Frequency Relationship
SAMPLE RESULT
KKKA 6923 Surface Water Hydrology
CONTENT
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
KKKA 6923 Surface Water Hydrology
2.13 Probable Maximum Precipitation
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.
KKKA 6923 Surface Water Hydrology
2.12 Probable Maximum Precipitation
HOW PMP can be determine using:
Meteorological method Statistical study of rainfall data; Pm = 42.16D0.475
KKKA 6923 Surface Water Hydrology
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