SIOUX FALLS, S.D. (KELO) — The snowpack in South Dakota may have been above normal so far this year but it’s not going to cause above normal chances of spring flooding.
The Vermillion River has an above normal chance of flooding over the next 90 days, according to the flooding outlook from the National Weather Service (NWS). It’s the only river with an above normal chance of flooding. The NWS released its forecast on Feb. 23. NWS said it will release a final outlook on March 9.
The U.S. Army Corps of Engineers said on Feb. 7 that drought conditions continue in the Missouri River Basin. The Feb. 21 drought monitor for South Dakota lists most of the state as abnormally dry or in moderate drought. The drought monitor is developed by National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration.
As of Feb. 7, the runoff in the Missouri River Basin above Sioux City, Iowa, continued to be below average, the U.S. Army Corps of Engineers said.
“Two to four inches of snow water equivalent (SWE) covers eastern Montana and much of the Dakotas,” the Army Corps said on Feb. 7. “Some areas in the central and eastern Dakotas are showing up to five inches of SWE.”
Snow from the Feb. 22-23 blizzard may have added some to the snowpack, but even with above-average precipitation over the past 90 days, it has not had much of an impact on the ongoing deficit, the NWS said.
Also, river levels are low across much of the state.
Although the Vermillion River has an above normal risk of flooding the greatest chances are for minor to moderate flooding at certain points on the river.
There is a 75% chance that river levels will exceed the minor flooding stage on the Vermillion River at Davis and Wakonda. There is a 50% chance it could exceed the moderate flood stage at those points and at Parker.
The NWS lists the Big Sioux at normal for possible flooding this spring as well as the West Fork of the Des Moines River in Iowa and the Redwood River in Minnesota.
There’s a 25% chance the Big Sioux River will exceed the minor stage for flooding at North Cliff Avenue. Sixteen feet is the minor flood stage. There’s a 10% chance it could reach 12 feet at Skunk Creek. The level for minor flooding at that point is 11 1/2 feet.
The Missouri River and James River are at below normal chances for flooding. So are the Rock, Little Sioux and Floyd rivers in Iowa.
There’s a 50% chance that the James River will exceed 11 feet which is at minor flooding in Huron, according to the NWS forecast.
Factors that could change the possibility of flooding include heavy rain, significant snowfall and rapid snowmelt. Ice jams could result in localized flooding.
The snow so far in 2023 and throughout the winter has drawn some comparisons to 1969 (1968-1969). Although the region has gotten snowfall amounts similar to some from that year, the spring flooding should not be as bad as 1969.
According to May 1969 report from the U.S. Department of Commerce’s Environmental Science Services Administration, the 1969 flooding was widespread.
The report cited significant snowmelt as the main cause of flooding.
The James River at Huron was expected to crest at 20 feet for a low and 21 feet for high. Flood stage was 11 feet. The actual crest was 16.7 feet, according to the U.S. Department of Commerce report.
The crest of the Big Sioux River in Sioux Falls reached 14.2 feet. Flood level was at 11 feet. The actual crest was lower than the forecast low of 16 feet and high of 18 feet.
Other parts of the Midwest had as severe or more severe flooding.