Many formulas have benn derived to express the relarionship between intensity and duration of point rainfall. For durations of 10 to 120min, the formulas of the general type which has been used in Japan are Talbot, Sherman and Kuno types.
For duration of 10 to 480min, in this paper, the relation between the average rainfall intensity and duration is more accurately expressed by a formula of the type I = a/(t^c+b), in which I is the average intensity for duration t, and a, b and c are constants having values dependent on locality. The rainfall data over 100mm per 24hr for a period of 33 years at Matsue were used to determine the values of a, b and c.