The Red River of the North is a complex river system in the north-central plains of the United States. The river continues to affect the people and property within its basin. During June of 2002, major flooding occurred for the third time in 5 years in the Red River of the North Basin, especially on tributaries in northwestern Minnesota. The worst damage occurred in Roseau, Minn., where about 95 percent of the town was inundated. Extensive damage to roads, bridges, and crops occurred throughout the flooded area in northwestern Minnesota and northeastern North Dakota. Roseau County, Minn., was designated a major disaster area on June 14, 2002, by President Bush and later twelve more counties were added to the disaster declaration. Unlike the 1997 floods, which were the result of record-high, region-wide snowpacks and a late spring blizzard, the June 2002 floods were the result of heavy rainfall that swept across the region on June 9-10 and again on June 22-24, 2002. Flooding in the Red River of the North Basin commonly is caused by spring snowmelt, and the severity of the flooding is affected by (1) substantial precipitation in the fall that produces high levels of soil moisture; (2) above-normal snowfall in the winter; (3) moist, frozen ground that prohibits infiltration of moisture; (4) a late spring thaw; (5) above-normal precipitation during spring thaw; and (6) ice jams (temporary dams of ice) on rivers and streams. Flooding during June 2002, however, was not caused by most factors usually associated with major flooding in the Red River Basin. In fact, precipitation had been below normal since late last summer and as of June 1, 2002, the flooded area was in a moderate drought based on the Palmer Drought Severity Index. The U.S. Geological Survey (USGS), one of the principal Federal agencies responsible for the collection and interpretation of water resources data, works with other Federal, State, and local agencies to ensure that accurate and timely data are available for making decisions regarding the public’s welfare (a listing of cooperators in the Red River Basin is given at the end of this report). This report presents preliminary meteorologic data provided by the National Weather Service, Grand Forks Office and water resources 2002 flood data that were obtained from selected streamflow-gaging stations located in the Red River of the North Basin (fig. 1). Historical peak stages and peak discharges and the June 2002 peak stages, peak discharges, and recurrence intervals are shown in table 1. The streamflow-gaging stations are listed in downstream order by station number, and station locations are shown in figure 1. The June 2002 peak stages and peak discharges given in this preliminary report may be revised as site surveys are completed and additional field data are reviewed in the upcoming months. The peak discharges are used to determine the probability, often expressed in recurrence intervals, that a given discharge will be exceeded in the future. For example, a flood that has a 1-percent chance of exceedance in any given year would, on the long-term average, be expected to occur only about once a century; therefore, the flood would be termed a “100-year flood.” However, the chance of such a flood occurring in any given year is 1 percent. Thus, a 100- year flood can occur in successive years at the same location. In some instances, recurrence interval estimates can be based on periods of regulated flow or made with historic adjustments when historic data are available.
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