FLOOD07038

• County: Statewide
• Community: All
• Stream Name: All
• Basin: South Platte
• Title: ASFPM Abstracts, etc. 1994
• Date: 1/1/1994
• Prepared For: ASFPM
• Prepared By: ASFPM
• Floodplain - Doc Type: Educational/Technical/Reference Information

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REA VY PRECIPITATION PAPER

by
Samuel E. Baker.
Milton E. Brown'

A comparative study of retum periods for 24-hour precipitation from two consecutive 30-year
periods (1930-1959 and 1960-1989).

With the current debate over climate change there is an interest in updating climate studies that
were done over 30 years ago.

Weather Bureau Technical Paper 40, Rainfall FreQuem;y Atlas of the United States was prepared
in 1961 using rainfall data primarily from the 1930 to 1959 period. Rainfall data from the
subsequent 30-year period is now available for analysis. This paper is a graphical comparison of
the 1930-1959 and 1960-1989 24-hour precip data sets for the Southeast U.S.

Return periods are determined using methods similar to those employed in the preparation of
TP-40. Two sets of maps win be prepared. Each map set will compare the original TP-40 data
to the 24-hour return periods computed from each of the two 30-year data sets. This graphical
comparison should help to answer the question as to the current applicability ofTP-40.

A later study will utilize statistical techniques in an attempt to determine if the two 30-year data
sets are significantly different

RELATIONSlllP TO CONFERENCE TOPIC:

Floodplain managers, planners and engineers all need the most accurate climatic extreme and
weather data to do their jobs well. Are the latest data better than those upon which many studies
are based? Do climatic extreme studies in use today need to be updated to reflect changes in the
climate? Many of the climatic extreme studies in use today were done over 30 years ago using
data that were collected in thll 30s, 40s and 50s. Since that time another 30 years of data have
been collected. Are these data more relevant to today's needs than those of 30 years ago?

Using a graphical technique, this study attempts to show the difference, if any, of two
consecutive 30-year data sets. The aim is to see if some of the old studies need to be updated
using the more recent data.

Samuel E. Baker, Service Hydrologist, National Weather Service Forecast Office, 2909 Aviation Way,
West Columbia, South Carolina 29170, Tel. [phone]

2

Milton E. Brown, Regional Climatologist, Southeast Regional Climatic Center, 1201 Main Street, Suite
1100, Columbia, South Carolina 29201, Tel. [phone]