Use of Design Storm Criteria in Florida

Design storm criteria consist of three parts: total depth, temporal distribution and the duration of the events. Since their publication, National Weather Service atlases. Technical Papers 40 and 49, and NOAA Atlas 2, have been the most commonly used sources for determining the total depth of a design storm. Soil Conservation Service (later Natural Resource Conservation Service) developed temporal distributions for 24-hour storms are widely used as the design criteria. Although the duration of a design storm would best be case specific, many permit agencies issues specified design storm durations. Water Management Districts in Florida issue their own guidance on design storms, including all three parts. In addition to the above-mentioned nationwide criteria, several Districts developed their isopluvial maps for rainfall depth for selected recurrence periods, temporal distributions for 24-hour or longer time periods, and the duration to use to design water resources structure. This paper compares these locally developed design storm criteria with Federally published ones, discusses methodologies used for developing these local criteria, and evaluates impacts of using different design storms on peak flow estimation. The paper also presents an approach to determine a proper duration to use.