Design Runoff Estimation Using an Efficient Rainfall Analysis Model for Low Data Available Catchment

Abstract

The challenge of various methods of analysis of rainfall intensity for design runoff estimation is in the availability of data for the given area. This work aims to evaluate the use of the Intensity Duration and Frequency (IDF) method in design runoff estimation using a rainfall analysis model for low data catchment areas such as Nigeria. The source of the data for the study is the Nigerian Meteorological Agency, and it is for Lokoja, a city in the North Central Zone of the country. Analysis of the data compared to the annual and partial duration series for rainfall intensities at various return periods. Also analyzed was the daily rainfall data to determine the rainfall intensity for the different duration and return periods for the study area. From the analysis, partial duration series analysis offered better design estimates than the annual series. Also noted is the fact that the intensity of rainfall increases with a return period of a given duration. The work also indicates that frequency curves can be used to extrapolate rainfall intensity of a given duration for a longer period than years of record. The paper, therefore, presents a design intensity equation useful for the estimation runoff necessary for sustainable infrastructures such as in water utilization and controls.