FLOOD06680

• County: Statewide
• Basin: Statewide
• Title: Flood Damage in the United States, 1926-2000
• Date: 6/1/2000
• Prepared By: NOAA
• Floodplain - Doc Type: Flood Documentation Report

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actual dollar amounts, rounded to three significant digits, The manual further advised, "Focus
attention on providing reasonable estimates of larger events (damages greater than $ 100,000)"
(NWS 1994, chap, 42, p. 10),

The field office procedures for collecting flood damage data have some notable strengths
and weaknesses, Damage estimators trained by their predecessors are likely to maintain
continuity in the data sets, because the training ensures that collection methodology does not
change from employee to employee, However, since the NWS operations manual is not always
used for guidance, employees may overlook changes in official NWS data collection policies,

C. Sources of Historical NWS Estimates
The NWS and the U.S, Weather Bureau published flood reports regularly in five
publications from 1918 through 2001. Table 2-1 summarizes the time periods covered and the
information provided by each of these sources, In the early years, damage estimates were
published only after major flood events, Annual reporting of flood damage throughout the U,S,
commenced in 1933,

From 1934 to 1975, the River and Flood Service published monthly flood reports and
annual summaries of flood damage by river basin, first in The Monthly Weather Review and later
in Climatological Data National Summary, Two formats were consistently used for the annual
summaries, one during 1934-1947, the other during 1948-1975, Annual damage estimates by
state for calendar years 1955-1975, and monthly damage estimates for the nation during 1925-
1975, were calculated and published in later reports (NWS 1975, 1977).

The 1978 annual summary issue of Climatological Data National Summary announced
"Compilation of the General Summary of National Flood Events and Flood Damage Statistics
has been delayed, These data will be published later," However publication of Climatological
Data National Summary ceased the following year,

For several years after the demise of Climatological Data National Summary, the only
published NWS records of flood damage were those included in Storm Data monthly reports,
As noted above, these reports often were incomplete and received little checking, Until 1995,
most damage estimates were indicated by marking a damage category, (Difficulties of using
estimates based on the damage categories are discussed in Section 4.) Until the mid-1970s, the
cause of damage was often listed as "heavy rain", rather than "flood", even when flood damage
was mentioned in the description, Flood descriptions gradually became more detailed in the
I980s, In general, the flood descriptions provide ample information about precipitation and river
flows, but only brief mention of damage.

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