What is a 100/500/1000 year rain event?

See Also: What is a 100/500/1000-Year Flood Event?


Hershfield, D.M., 1961. Rainfall Frequency Atlas of the United States, Technical Paper No. 40. Weather Bureau, US Department of Commerce, Washington, DC.

This started the 100 year rain event system. Although it was never intended to be about flooding, the notion of a 100 year event was later incorporated into the NFIP when it was passed in 1968.

Faiers, Gregory E., J. M. Grymes III, Barry D. Keim, and Robert A. Muller. “A reexamination of extreme 24-hour rainfall in Louisiana, USA.” Climate Research 4, no. 4 (1994): 25-31.

As more data was accumulated since the 1961 report, it became clear that there were more extreme rain events in Louisianan than were predicted by the model. This shows the pattern that the calculated probability for extreme events (whether they are 10 or 100 year or 500 year events) increases (they are seen as more frequent) as more data is accumulated through time.

Faiers, Gregory E., Barry D. Keim, and Robert A. Muller. Rainfall frequency/magnitude atlas for the south-central United States. Geoscience Publications (1997)

This is an update of the 1961 report, adding more years of data, more rain gauges, and beginning to consider climate change. It notes that there has been an increasing incidence of extreme rain events in the south since the 1961 report.

Faiers, Gregory E., and Barry D. Keim. “Three-hour and twenty-four-hour rainstorm ratios across the Southern United States.” Journal of Hydrologic Engineering 13, no. 2 (2008): 101-104.

Keim, Barry D., Royce Fontenot, Claudia Tebaldi, and David Shankman. “Hydroclimatology of the US Gulf Coast under global climate change scenarios.” Physical Geography 32, no. 6 (2011): 561-582.

Powell, Emily J., and Barry D. Keim. “Trends in daily temperature and precipitation extremes for the southeastern United States: 1948–2012.” Journal of Climate 28, no. 4 (2015): 1592-1612.



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