Application of Huff Rainfall Distributions in Stormwater Management | Journal of Sustainable Water in the Built Environment | Vol 9, No 1

AbstractHuff rainfall temporal distributions published in Atlas 14 are contrasted with rainfall distributions with nested intensity-duration-frequency functions that are also derived from Atlas 14, and the role of Huff rainfall distributions in the design of stormwater-management systems is assessed. Results show that Huff distributions generally underestimate average rainfall intensities for shorter-duration time intervals, which makes them not acceptable for designs based on peak runoff rates. In the design of detention basins to control site discharge rates for a given return period, the results show that in many cases conventional detention-basin designs based on nested rainfall distributions will perform inadequately in response to the more realistic Huff rainfall distributions. Overall, the results indicate that Huff rainfall distributions should be incorporated in sizing detention basins to ensure that peak postdevelopment discharges do not exceed peak predevelopment discharges for given design return periods.Practical ApplicationsSite development usually results in postdevelopment peak runoff rates exceeding predevelopment peak runoff rates for given return periods. Stormwater-management regulations and/or best professional practice generally require that peak offsite discharges not be increased by development, and onsite detention basins are commonly used to attenuate postdevelopment runoff rates. Analyses to effectuate this outcome are usually based on using synthetic extreme rainfall distributions derived from Atlas 14, while not considering the more realistic Huff rainfall distributions that are also available in Atlas 14. The results of this investigation show that the Huff rainfall distributions should be incorporated in sizing detention basins to ensure that, under realistic circumstances, peak postdevelopment discharges from a site do not exceed peak predevelopment discharges for a given return period.

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