College of Engineering

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Browsing College of Engineering by Subject "Annual maximum series"

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    Development Of Intensity- Duration- Freqency-Curves For Kumasi
    (September, 2013 ) Abubakari, Sulemana
    This work involves the development of IDF Curves for the city of Kumasi. Annual Maximum Rainfall depths of various durations over twenty-two years for Kumasi were obtained from the Ghana Meteorological Services in Accra. A check for the consistency of data found the data inconsistent and so the double mass curve was used to make the data consistent and also allowed for filling in gaps where data were missing. The data set thus obtained was then subjected to frequency analysis to determine the distribution which best characterize the data set. The annual maximum series were found to be drawn from the Gumbel distribution whose parameters were computed by fitting the statistics to the data. The Chi-square test and the Kolmogorov-Smirnov test prove the appropriateness of the fitting. Since the data available was only 22 years, IDF values for return periods higher than 22 years were obtained using frequency factors. The IDF estimates resulting from this work have been compared with the existing IDF curves prepared by J.B Danquah. The results show that for shorter durations(12 min and 24 min),the new IDF Curves give higher intensities for the same return period whiles for longer durations(42min, 1 hr, 2hr,3hr,6hr,12hr and 24 hr), the new IDF Curves give lower intensities for the same return period. Sub-Hourly IDF Curves for various durations were derived using the Hourly AMS and WMO factors. The derived Sub-Hourly IDF Curves have been compared with the Sub-Hourly IDF Curves computed from actual data. Comparison of the two comes out with a relationship which could be useful in obtaining Sub-Hourly IDF estimates for areas where only hourly data are available. In general, the results show that shorter duration storms are becoming more intense while longer duration storms are becoming less intense.