FLOOD06548

• County: Statewide
• Community: na
• Basin: Statewide
• Title: National Water Summary 1988-89
• Date: 12/1/1989
• Prepared By: USGS
• Floodplain - Doc Type: Educational/Technical/Reference Information

FOREWORD

National Water Summary 1988-89--Hyd1'OIogic Events and Floods arid Droughts is
the sixth in a series of reports that dt:scribc the condition and characteristics of the
water resources of the United States. This volume of the series describes some of
the most memorable floods and droughts of record, as reflected in the long.tenn
streamflow records of each State, and is the most comprehensive report to date on the occurrence
of extreme hydrologic events in the United States. For the first time, historic extreme hydrologic
events in each State are presented in the context of climate and the pathways by wbich moisture,
eva.porated from the oceans, Great Lakes, and land arcas, is conveyed by the atmosphere to the State.
Floods and droughts are among the most frequent and costly of natural disasters, both in tenns
of human hardship and economic loss. Floods usually are local, transient events that strike suddenly,
some with little or no warning, and raise havoc and destruction along the course of streams and
rivers. As much as 90 percent of the damage related to natural disasters (not including droughts)
is caused by floods (including mud and debris flows). The lO-year (1979-88) average annual estimated
flood damage is $2.4 billion, and the long-term (1925.-88) annual average for lives lost is 95, mostly
as a result of flash floods. One only has to recall the flash flooding of the Big Thompson River
in Colorado in 1976 that swept through campgrounds <lnd vacation homes nestled in a narrow canyon
and killed 139 people to realize how unexpected and costly, in human life alone, such phenomena
caI1 'De.
Droughts, on the other hand, affect human activities gradually as precipitation deficits
accumulate over a period of months and coolmonl)' years. The cumulative effects of these deficits,
ofttn temporarily offset by brief periods of rainfall, reduce streamflow and reservoir storage at a
time when water demand increases. In historic times, precipitation deficits and their cumulative
eff~cts drastically reduced food supplies, c;:msing widespread famine; in modern tirnes, this type
of calamity still Occurs in parts of Africa and Asia. Developed countries have established interna-
tiorlal food procurement, storage, and distribution system.s that compensate for variations in supply,
but even so, the economic loss and hardship associatt~d with regional, multiyear dr0l1ghts, such as
the one that has affected California from 1987 to the present, can have long-term, but difficult to
quantify, effects on crops, operating costs, industrial production, and the environrrlent.
On December I, 1987, the United Nations passed a resolution by unanimou; consent that
supported the establishment of the International Dc\:adc for Natural Disaster Redoction, which
encourages all nations to reduce the loss of life llnd propcrty damage and to minimizc social and
economic disruption from natural hazards during 1990--2000. The U.S. Geological Survey i5
conlmitted to international cooperation in this effort and in transferring and making availa.ble the
tedlnology developed over the years to characterize natural hazards. With respect to extreme
hydrologic events, the U.S. Geological Survey has (~OndUClcd research for many years to better
understand the physical processes that lead to floods and droughts, measured these evcntsj and prepared
hazard maps and other sources of information 10 help planners mitigate the effccts of extreme
hydrologic events and to develop loss-reduction ffiI,:asures. Data telemetered from atmut 3,400 of
the nearly 7,400 slream gages that are operated by the U.S. Geological Survey are available to the
National Weather Service to forecast floods for more than 20,(X)() communities. In cooperation with
the National Weather Service and local agencies, many of these stream-gaging stations are used
for flood-alert systems to provide timely warning of flash floods. The U.S. Geological Survey also
has mapped many of the Natioo's flood plains to a~;si:it agencies that regulate development on the
flood plains.
Routinely, and particularly during times of drought, the U. S. Geological Survey provides
water-management agencies with information on the status of streamflows and ground-water levels
for lIse in the management of water supplies. Perhaps more importantly, the U.S. Geological Survey
provides water-resources assessments that identify the quantity and quality of existing water supplies
and their current use. Such assessments commonly are used to identify and quantify alternative supplies
for use in time of drought. Historic data can be used to simulate drought conditions and to determine
under what circumstances alternative water-conservation measures should be applied and what changes
in water-management operations optimize the use of the remaining water supplies.

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