Development of Intensity- Duration- Frequency Curves for Koforidua

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June 2016
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The estimation of rainfall intensity for a particular frequency is normally required for design of hydraulic and water resources engineering control structures. The main objective of this paper is to develop IDF curves for Koforidua based on recent rainfall information. Annual Maximum Rainfall depths of various durations over twenty-nine years for koforidua were obtained from the Ghana Meteorological Services in Accra. A check for the consistency of data found the data inconsistent and linear regression analysis 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 Kolmogorov-Smirnov test proves the appropriateness of the fitting. The tread follow the usual Intensity-Duration-Frequency-curves and equation has also been developed for particular frequency. By using easy fit software, Gumbel Extreme type one was found to be the best distribution for the analysis. The Intensity- Duration-Frequency-Curves obtained for the study area has generally characteristic form of Intensity-Duration-Frequency-Curves. There should be a revision of the Intensity-Duration-Frequency curves for all the major cities and towns in Ghana to take into account the effect of climate change. Meteorological services department must be strengthening in data processing, data collection and storage.
A thesis submitted to the Department of Civil Engineering, College of Engineering in partial fulfillment of the requirements for the degree of Master of Science Water Resources Engineering and Management, 2016