ABSTRACT

This paper presents results of a study carried in Zimbabwe aimed at analysing the frequency of Nyanyadzi River floods using the Gumbel distribution. Extreme floods over recent years had washed away fields, destroyed infrastructure and killed animals. It was hypothesised that Nyanyadzi flood flows obey the Gumbel distribution. The scale and shape parameters of the distribution were estimated using method of moments. Maximum instantaneous flow data covering 30 water years (1969-1999) for station E119 on Nyanyadzi River were collected from the Zimbabwe National Water Authority (ZINWA). A Chisquare ?2 test revealed no significant (p =1.000) differences between recorded and predicted flood flows. Due to goodness of fit of the Gumbel distribution, it was assumed to be appropriate for modelling frequency of Nyanyadzi River floods. The magnitudes of the 100 and 200-year floods were estimated to be 276 and 310 m3/s respectively.