Adjustment factors for restricted rainfall

6-minute rainfall data were used to calculate average adjustment factors for rainfall durations 1, 2, 3, 6, 12 and 24 hours at seven locations (Adelaide, Brisbane, Darwin, Hobart, Melbourne, Perth and Sydney). When combined with results from published studies, average values of 1.14 for 24-hour annual maximum rainfalls and 1.16 for sub-daily rainfalls were derived. Considering the large variability in adjustment factors among the various locations and studies, it is recommended that an average value of 1.15 be used for rainfall durations from 1 to 24 hours. There is some indication that adjustment factors for 24-hours duration decrease as the magnitude of the rainfall increases, and reduced factors for large daily rainfalls seem appropriate, but this reduction for large rainfalls was not evident in the sub-daily rainfalls. There is evidence from UK studies that the adjustment factor should be reduced for multiple day storm totals.