Rainfall Variability: Implications for Flood Frequency in Sokoto, North-Western Nigeria

Abstract

Rainfall in the Northern part of Nigeria in general and that of Sokoto in particular varies in space and time. The variability is so marked that it has a devastating effect on the socio-economy of the place. This present studies assessed the variability of rainfall by considering its magnitude, frequency seasonality of occurrence and its implication for flood frequency in the area. The specific objectives of the study include (i) to analyze the variability in rainfall over a period of 62 years (1949-2010), (ii) to examine the relationship between rainfall variability and flood frequency in the study area (iii) to determine the period of flooding in the area and (iv) to examine the adaptation and mitigation options for management of flood in the area. To achieve these, rainfall data for 62 years (1949-2010) and evapotranspiration for the same period for Sokoto station was used, the Spearman rank correlation coefficient was used to ascertain the trend in rainfall, the Standardized rainfall anomaly index was used to examine the variability in rainfall, The Gumbel extreme value distribution was used to determine the magnitude and frequency of extreme rainfall and hence, the recurrence interval for flood occurrence. The results of the study revealed that rainfall in the area is on the increase with a positive correlation of 0.08 which was found to be significant at 95% confidence level