Flood Estimation from Short Records

Peak flood flows are highly correlated with the daily flows in which they occur, and this relationship is used to develop a method of extending short flood records. The frequency distribution of daily flows, estimated from daily rainfalls by a rainfall-runoff model, is used with the short flood record to estimate the long-term distribution of floods. Tests were made on 8 catchments, 67 sq miles to 505 sq miles in area, in Queensland, Australia, using 10 yr of streamflow record in each case with daily rainfalls to estimate 30 yr to 35 yr of floods. Log-normal and Log-Pearson III distributions were fitted to both estimated and actual flood series. The estimated 1 in 50 yr and 1 in 100 yr floods differed on average by less than 8% from the actual records.