In many aspect of our life, the understanding of the frequency of occurrence of certain events will contribute greatly to our planning, design and organisation of any activities. The knowledge of the frequency of occurrence of extreme rainfall events for a certain duration, for example will be important to engineers in designing dams, culverts, draining system, structures that are susceptible to damage by heavy rainfall and also for modelling the flood forecast.
 
Since design and planning are concerned with future events whose time or magnitude cannot be  forecast, we must resort to statements of probability or an estimate of the frequency with which a specific rate or volume of flow/rainfall will be equaled or exceeded in the future and this is based upon a study of the frequency with which it has been exceeded in the past.
 
The rainfall intensity- return period for several meteorological stations in Malaysia were calculated for the purpose of providing the related agencies in the water resources management with the relevant information.