ABSTRACT
Inadequate
meteorological data for accurate designing, operation and planning of water
resources against extreme rainfall event is a major challenge confronting
engineers. Thirty two (32) years (1983-2014) daily rainfall data were collected
for Port Harcourt, Calabar, Umuahia, Owerri, Benin, Warri, Enugu, Onitsha,
Ibadan and Lagos from Nigeria Meteorological Agency (NIMET), Oshodi, Lagos
State for the study. The method of annual maximum series was used to select
data sets for rainfall analysis. Rainfall
anomaly index and trend lines were plotted for each location to study the
pattern of rainfall. Gumbel and Log Pearson Type 111 distributions were used to
compute the observed rainfall intensity values at durations of 10, 15, 20, 30,
60,120,180,240, 300 and 360 minutes for return periods of 2, 5, 10,20,50 and
100 years. To obtain parameters for the IDF models for each location, the
computed rainfall intensities were subjected to non-linear regression analysis using
Microsoft Excel Optimization Technique Solver wizard for the respective
durations and return periods. From the standardized anomaly index graphs,
Calabar, Owerri, Warri, Onitsha, Benin, Enugu, Lagos, Ibadan, Port Harcourt and
Umuahia had the highest positive rainfall anomaly index above average in the
years 2010, 1996, 2008, 1995, 2011, 1997, 1988, 2014, 2006 and 1997,
respectively, while their lowest negative rainfall anomaly index below average
were in the years 1996, 1983, 1987, 1983, 2005, 2000,2008,1983,1983 and 1983,
respectively. It is quite evident from the results, that the year 1983 had
minimum amount of rainfall in most study stations. The trend analysis result showed
that there is fluctuating rainfall pattern across the observed years. Though,
each station had different trend. Port Harcourt had an annual rainfall trend
that indicated a relatively steady increase. Owerri and Umuahia trend movement
showed a decrease in annual rainfall and Lagos trend showed a relative steady
decrease. All other stations showed a trend movement of annual rainfall
increase. The inter-annual rainfall variability in all the study areas is due
to climatic change. The IDF Models developed are for Enugu
𝐼=The performance of the models were
analyzed by determining the chi-square(χ2 ), coefficient of determination(R2
) and Root Mean Square Error(RMSE) of the fitted distributions. From the
analysis, the R2 values ranged from 0.76-1.00 and the RMSE from
0.04-15.92 for the Gumbel distribution for the studied locations. Also for the
Log Pearson Type 111 distribution, R2 values ranged from 0.98-1.00
with RMSE of 0.01-15.33 for the studied locations. Log Pearson Type 111 distribution ranked first
with respect to R2 and RMSE for the IDF models, but no significant
difference amongst the predicted intensities of the various IDF models. Log Pearson Type 111 Model is recommended for
the prediction of rainfall intensities for the studied locations. The Intensity
Duration Frequency (IDF) Models (results) developed will serve as tools for the
Engineers and Hydrologists in estimating storm water runoff from a watershed
for the design of drainage systems, reservoir management and planning of water
resources development.. This will mitigate flooding and its consequences. Also
the findings when applied as demonstration tools in teaching land drainage
courses to Engineering students, will enhance their understanding and
appreciation of the course.
CORDELIA, C (2024). Development Of Rainfall Intensity-Duration Frequency Models For Selected Locations In Humid Rain Forest Zones Of Nigeria:- Emeka-Chris, Cordelia C. Mouau.afribary.org: Retrieved Dec 24, 2024, from https://repository.mouau.edu.ng/work/view/development-of-rainfall-intensity-duration-frequency-models-for-selected-locations-in-humid-rain-forest-zones-of-nigeria-emeka-chris-cordelia-c-7-2
CHIKA, CORDELIA. "Development Of Rainfall Intensity-Duration Frequency Models For Selected Locations In Humid Rain Forest Zones Of Nigeria:- Emeka-Chris, Cordelia C" Mouau.afribary.org. Mouau.afribary.org, 29 Apr. 2024, https://repository.mouau.edu.ng/work/view/development-of-rainfall-intensity-duration-frequency-models-for-selected-locations-in-humid-rain-forest-zones-of-nigeria-emeka-chris-cordelia-c-7-2. Accessed 24 Dec. 2024.
CHIKA, CORDELIA. "Development Of Rainfall Intensity-Duration Frequency Models For Selected Locations In Humid Rain Forest Zones Of Nigeria:- Emeka-Chris, Cordelia C". Mouau.afribary.org, Mouau.afribary.org, 29 Apr. 2024. Web. 24 Dec. 2024. < https://repository.mouau.edu.ng/work/view/development-of-rainfall-intensity-duration-frequency-models-for-selected-locations-in-humid-rain-forest-zones-of-nigeria-emeka-chris-cordelia-c-7-2 >.
CHIKA, CORDELIA. "Development Of Rainfall Intensity-Duration Frequency Models For Selected Locations In Humid Rain Forest Zones Of Nigeria:- Emeka-Chris, Cordelia C" Mouau.afribary.org (2024). Accessed 24 Dec. 2024. https://repository.mouau.edu.ng/work/view/development-of-rainfall-intensity-duration-frequency-models-for-selected-locations-in-humid-rain-forest-zones-of-nigeria-emeka-chris-cordelia-c-7-2