Development of Rainfall Intensity- Duration-Frequency constants, curves and nomograph for selective stations of Pune district
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Date
2015
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MPUAT, Udaipur
Abstract
Rainfall is the result of complex atmospheric phenomena and it is a complicated temporal and spatial structure. A wide range of frequency-content features and extreme variability over time intervals from a few seconds to years make rainfall an interesting and challenging process to study. Rainfall is varying from one location to another and not having same intensity and frequency, thus there is need to develop Intensity-Duration-Frequency (IDF) location specific constants.
Rainfall Intensity-Duration-Frequency relationship and nomographs are required for design of soil and water conservation structures. The rainfall IDF relationship can be expressed as, I = K Ta / (t + b) d Where, I is maximum rainfall intensity (cm/h), T is return period (years), t is Duration (h) and K, a, b and d are location specific constants.
For the location specific constants in above equation, it is required to evaluate the rainfall IDF relationship. The present study was undertaken to develop the rainfall IDF relationship and nomographs for five stations viz. Ambeghar, Nasrapur, Deoghar, Pangari and Sangvi Bk. of Pune district (Maharashtra).
For the IDF analysis, the automatic rainguage charts (mass curves) were collected from Pune sub division of Hydrology project. The rainfall charts of 18, 13, 11, 14 and 14 years for Ambeghar, Nasrapur, Deoghar, Pangari and Sangvi Bk. were analysed for maximum annual rainfall intensity for selected durations viz. 0.08, 0.16, 0.25, 0.5, 0.75, 1, 2, 3, 6, 12 and 24 hours. The plotting positions were obtained by using the ‘Computed Method’ for development of frequency lines. The value of constants ‘a’ and ‘b’ were determined by using graphical method whereas the values of ‘K’ and ‘d’ were determined using least square method.
The values of constants K, a, b and d were found to be 3.291, 0.148, 0.02 and 0.598 for Ambeghar; 4.688, 0.125, 0.20 and 0.821 for Nasrapur; 4.220, 0.143, 0.01 and 0.487 for Deoghar; 4.415, 0.117, 0.01 and 0.577 for Pangari; 3.928, 0.171, 0.15 and 0.781 for Sangvi Bk. Further the nomographs were developed by using method suggested by Luzzadar (1964) for the IDF relationship for the said stations. It was finally analysed through the comparison of calculated and evaluated value of rainfall intensities are within the permissible limit of error percentage and thus the developed IDF relationships and nomograph can be used for further studies.
Description
Development of Rainfall Intensity- Duration-Frequency constants, curves and nomograph for selective stations of Pune district
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Citation
Achpal and Achpal , 2015