Abstract Flooding due to excessive rainfall is a frequent hazard in the flood plains of River Malaba catchment. This paper documents the study that involved predicting of the annual peak flows for river Malaba catchment, determining its magnitude and predicting the extent of flood depth within its flood plain. The flow data was analysed to ascertain its applicability and reliability for frequency analysis. F-test and t-test were conducted to check the stability of the data’s variance and mean respectively. The technique involved the use of observed annual peak flow data to compute statistical information such as mean values, standard deviation, skewness and recurrence intervals. The statistical data were then used to construct frequency distributions. Log-Pearson Type III distribution was used to predict the annual peak discharge of the river for the period 1950 to 1980. The results obtained indicated that the peak flow values for river Malaba were increasing with increasing return period. The estimated discharges obtained for each return period were used to model the flood using HEC-RAS and ArcGIS. There was a general increase in the predicted size of the flood plain with increasing return period. A DEM of a better resolution than 90 Meters is envisaged to result in better flood depth results. The use of directly generated coordinates to delineate the stream flow paths is recommended. The flood frequency results from this study can be used as a guide in determining the capacity of such structures as highway bridges and culverts.