Derivation of the Rainfall Intensity, Duration and Frequency Equations for Makurdi, Nigeria

Information and adequate data on intensity–duration–frequency of rainfall are regularly required for a variation of hydrologic, environmental and hydraulic applications. This paper presents rainfall intensity-duration-frequency equations for Makurdi, Nigeria. Rainfall intensities from Makurdi were used to establish empirically derived constants for about thirteen different equations. These equations were evaluated statistically using analysis of variance (ANOVA), total error, model of' selection criterion (MSC), Coefficient of Determination (CD), Correlation coefficient (R) and Akaike Information Criterion (AIC), with the main objective of selecting the best equation for the location. The study revealed that rainfall intensity can be expressed in terms of either the amount of rainfall time only, frequency or both duration of the rain and time of return with empirically derived constants. Statistical evaluation revealed that the correlation coefficients of equations for Makurdi were between 0.896 and 0.894, respectively. Model 12 was discovered to be most accurate model for prediction of rainfall amount as against model 15 presented in literature. The model had the highest correlation coefficient for Makurdi. According to findings, functions of the duration of rainfall, return time, and empirically derived constants are the best functions, which explains the severity of the rain the best based on the values of MSC, CD, AIC and R.