An Analysis of the Cycles and Periodicities of Annual Rainfall over Awka Region, Nigeria

Abstract

The aim of this study was to analyse the cycles and periodicities of annual rainfall over Awka region, Nigeria. This is necessitated by the fact that, despite the fact that wet years contribute greatly to annual flooding and gully erosion observed in the area, researches on cycles and periodicities of rainfall in the area are obviously lacking. This research is, therefore, an attempt to close this gap in knowledge. 35 years rainfall data (1975-2010) were collected from the Nigerian Meteorological Agency (NIMET) Lagos from which harmonic calculation was made using Harmonic Analytical Technique. The model produced 13 harmonics (cycles) of which those of 1, 6 and 11 with amplitudes of 181.66 mm, 149.42 mm and 126.63 mm and periodicities of 35, 5.20 and 2.84 were isolated as most important. All calculations were performed using MINITAB version 16 statistical programme running under PC/Windows 98. Following from the findings, it was suggested that Urban and Regional Planners, Geomophologists and Engineers could use the result to develop a flood and erosion management plan for the area.