Statistical analyses of flood frequency, low-flow frequency, and flow duration of streams in the Philadelphia Area, Pennsylvania

Flood frequency, low-flow frequency, and flow-duration characteristics were computed for 26 stream-gaging stations in and near Philadelphia. Data were obtained from 21 continuous-recording stations and five stations that were initially continuous-recording stations, but which were subsequently converted to crest-stage stations. The annual peak flows were fitted to the three-parameter log-Pearson Type III distribution to develop the flood- frequency characteristics. The range of the reported annual recurrence intervals for flood-frequency depends on record length. Low-flow frequency characteristics for various numbers of consecutive days were also defined by fitting data to the log-Pearson Type III distribution. Standard analyses of daily discharges produced the duration curve characteristics. Results of these analyses are tabulated.