Extreme rainfall intensities

Abstract

Statistics of the total time, in minutes, that extreme rainfall rates are exceeded were computed from weighing raingage records at stations in several rainfall regimes. The results are presented on maps, frequency diagrams and as analytical expressions. Measures of areal variability were calculated from data at seven stations within an 8 km 2 area. The total-time-intensity data have only an imprecise relationship to clock-hour frequencies, the shortest duration rainfall data published regularly. Zusammenfassung Extreme Niederschlagsintensit~itenStatistiken der Gesamtzeit in Minuten, in der extreme Niederschlagsmengen tiberschritten waren, wurden aus Niederschlagsregistrierungen in verschiedenen Niederschlagssystemen berechnet. Die Ergebnisse werden in Karten, in H~iufigkeitsdiagrammen und in analytischen Ausdrticken dargestellt. Verh'altnisse der r/iumlichen Variabilit~it warden aus Daten an sieben Stationen in einem etwa 8 km 2 grot~en Gebiet errechnet. Die Gesamtzeitintensitgten (TTI) haben nut eine ungenaue Beziehung zu stiindlichen H/iufigkeiten.

Deriving rainfall intensity-duration-frequency relationships and estimates for regions with inadequate data

“…The few cases in which the fitting was not good were either for 0.2 or 0.4 h durations. This may not be surprising for as Hershfield (1962) noted such high intensity-rainfall-frequency data are not usually accurate and could be subject to large errors due mainly to sampling deficiencies. The estimates of 1/a, g and IDF values should therefore prove reliable and useful.…”

Regional rainfall depth‐duration‐frequency equations for Canada

“…This high degree of consistency in short-duration rainfall frequency data implies that local convective rainfall cells have similar physical properties irrespective of geographical location. While this hypothesis has never been verified for Canadian conditions, it has been advocated in other studies [Hershfield, 1961, and1962 …”

“…Thus a better fit to the observed data is obtained in this study by separating short-duration (t -< 2 hours)from long-duration (t > 2 hours) rainfall events since short-duration convective storms are physically based on different meteorological factors than longer-duration frontal storms. Several other studies [Hershfield, 1961, and1962;Bell, 1969;Penta et al, 1972;Ferreti andFerro, 1990, 1992;Ferro, 1993] Tables 8 and 9 show that while the AES equation provides a better fit to the SEV1 model at station 1018610 in British Columbia and 8401700 in the Maritimes, discrepancies between design storms estimated by the single-site equation and the proposed regional equations amount to as much as 39% and 24%, respectively.…”

“…Thus a better fit to the observed data is obtained in this study by separating short-duration (t -< 2 hours)from long-duration (t > 2 hours) rainfall events since short-duration convective storms are physically based on different meteorological factors than longer-duration frontal storms. Several other studies [Hershfield, 1961, and1962;Bell, 1969;Penta et al, 1972;Ferreti andFerro, 1990, 1992;Ferro, 1993] have also recognized that the two types of storms follow different IDF relationships. Tables 6 and 7 indicate that the fit of the AES equation to the SEV1 frequency model is as good as that of the RDDF equations to the HRGEV model at station 3012208 in Alberta and 1108447 in British Columbia.…”

Influence of Rainfall Characteristics on Total Suspended Solids in Urban Runoff: A Case Study in Beijing, China

“…The P&C method was designed to overcome the problem of missing time sequences of intensities, and used rainfall data of the same duration (including intense bursts) that were typically used to develop IDF curves. Neither the P&C method nor the K&C method use the rainfall pattern of complete storms, in contrast to other methods, e.g., Hershfield [30], Huff [31], Pani and Haragan [32], and Asquith, et al [33].Mou [34] applied the P&C method to long-term heavy rainfall events in Beijing central districts to derive rainfall distributions for three P&C design storm durations (60, 120, and 180 min). These P&C distributions give the percentage of rain falling in each 5-min interval and are used in this study.…”