ABSTRACT:
Precipitation depths for high magnitude, low frequency storm events are critical inputs in designing hydraulic and erosion control structures for soil and water conservation. The common standard for precipitation magnitude and frequency data prior to 2004 was National Weather Bureau Technical Paper 40, which has been superseded by National Oceanic and Atmospheric Administration (NOAA) Atlas 14. Comparison between these two reports for Midwestern sites with long climate records reveals important changes in design storm events; in some cases event magnitudes increased up to 46 percent. The 24-hour 100-year recurrence interval precipitation depth increased at 89 percent of study locations, but there was little change in events with 2- and 10-year recurrence intervals. These changes most likely result from increased accuracy in precipitation statistics and localized patterns of increased storm magnitude. Because of the impact of these changes on the design of hydraulic and erosion control structures, design manuals and local ordinances should be updated to reflect the new data.
Footnotes
Carrie E. Davis Todd is a graduate research assistant in the Department of Earth and Atmospheric Sciences at Purdue University in West Lafayette, Indiana. Jonathan M. Harbor is professor and department head in the Department of Earth and Atmospheric Sciences at Purdue University in West Lafayette, Indiana. Benjamin Tyner is a statistical consultant in the Department of Statistics at Purdue University in West Lafayette, Indiana.
- Copyright 2006 by the Soil and Water Conservation Society
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