CAUSAL FACTORS OF URBAN FLOODING IN ANAMBRA STATE, NIGERIA

Abstract

Various causes of flooding in Anambra state (Awka and Onitsha) were looked at in a broad way to determine the meteorological, natural, anthropogenic/human factors that encourage flooding, and the flooding potential of the study area using physical factors. A fifteen year rainfall data was used to determine the departure of rainfall from normal for Awka and Onitsha. Severe flood would be expected in the year 2009 while no flood will be expected in the year2001, 2006 and 2010, whereas moderate flooding should occur in many other years. The monthly mean rainfall (1998-2012) shows a noticeable steady rainfall from May to August while the maxima of rainfall were recorded in September. Natural/physical factors responsible for flooding in the study area, are water bodies and tributaries in and around Awka and Onitsha, different soil type (Acrisols, Lixisols, Nitisols, and Fluvisols) and the slope (elevation) of the study area. All these contribute to flooding in different degrees in any particular area. From the combination of these flood-causing parameters and derivation of their respective critical index values, the flooding potential of the study area was obtained. Analysis of the questionnaire on public opinion shows that, flooding in particular and poor waste management are the two important environmental problems in Anambra state.