Precipitation in the Northern Plains, September 1996 through April 1997

Abstract

Floods are a common occurrence on all major streams and rivers of the United States. Many floods are just a minor nuisance when low-lying fields and roads are inundated; however, major floods that result in loss of life and extensive damage occur on a number of the Nation's rivers each year. Know ledge of the flood characteristics of the Nation's streams and rivers is important for preventing the loss of life and mitigating the ever-increasing costs of flood damages. The U.S. Geological Survey (USGS) plays a critical role in supporting flood mitigation, flood forecasting, and response and recovery efforts during and after floods. The 18,000 streamflow-gaging stations that have been operated by the USGS at some time since 1889 provided much of the base information for assessing flood risk and for designing infrastructure such as dams and levees that minimize flood damages. The streamflow-gaging stations also provide data that are critical to effective management of the Nation's water resources. The USGS has a current network of 7,000 streamflow-gaging stations. Of these stations, 4,200 are used to provide real-time streamflow data 24 hours a day directly to the public and many organizations, including the National Weather Service, U.S. Army Corps of Engineers, the Bureau of Reclamation, and the Federal Emergency Management Agency. These and other Federal, State, and local agencies use the river-stage data to forecast river conditions, to issue flood warnings and river-conditions statements, to plan flood response and recovery operations, and to plan reservoir releases or water withdrawals. With the advent of the internet, USGS data, real-time and historical, are being disseminated to an even broader range of interested users worldwide. This report, "Precipitation in the Northern Plains, September 1996 through April 1997 ," is an example of the type of information produced by the USGS streamflow-gaging network. The report is the first in a two-part series of reports that document the 1997 spring floods in the northern plains. The report describes precipitation and climatic conditions before and during the floods. U.S. Geological Survey Circular 1185-B, "Peak Discharges and Flow Volumes for Streams in the Northern Plains, 1996-97 ," is the second in the two-part series of reports and presents the magnitude and duration of discharges and volumes, describes the effects of reservoir storage on flood peaks, and summarizes the effects of the 1997 spring floods on the people of the northern plains.

Caveant admonitus (“Let the forewarned beware”)

“…During the winter of 1996‐1997 these factors produced a catastrophic regional snowmelt flood with an estimated return period of between 100‐200 years (Macek‐Rowland et al , 2001b). Total direct flood damages within the Grand Forks, North Dakota/East Grand Forks, Minnesota metropolitan area exceeded $2bn, making it the most costly flood, on a per capita basis, for a major metropolitan area in US history (Macek‐Rowland et al , 2001a). The absence of any spring rain‐on‐snow during the melt period means that an even larger spring flood event is physically possible.…”

“…Macek‐Rowland et al (2001a) review the hydroclimatological events that produced the 1997 Red River Valley Flood, while Todhunter (2001) summarized the general snowmelt hydrology of the flood event. An analysis of the flood hydraulics for the Grand Forks flood is presented in US Department of Commerce (1998), while Pielke (1999) has reviewed the flood forecasting and decision‐making processes for the flood.…”