Rainstorm Intensity–Duration–Frequency Model for Tarkwa, Ghana

Rainstorm intensity–duration–frequency relationship is a tool required for appropriate planning and designing of drainage systems. In this study, 22 years of annual peak daily rainstorm data distribution was tested to verify if it followed Lognormal, Gumbel, or Log Pearson Type III distribution. The distribution to which it belonged was used to build rainstorm intensity model of 0.5, 2, 5, 8, 10, 12, 15, 18, and 24 h durations. The findings revealed that the observed peak annual rainstorm followed Gumbel and Log Pearson Type III distributions at 0.05 significant level. Sherman rainstorm intensity model was also adopted and the parameters determined. Data generated with the Gumbel distribution function best fitted the Sherman model followed by those by log Pearson Type III. The rainstorm models developed with Sherman’s equation were recommended for use in the Tarkwa area. Keywords: Flood, Gumbel Distribution, Water Resources, Rainstorm