With all this snow on the ground and the heavy rain in the forecast, the result will be a sloppy mess of water issues.
Mike Gillispie, hydrologist at the Sioux Falls National Weather Service, has been eyeing these spring floods for many years and says the ingredients are on the table for major flooding on area rivers, including the Big Sioux.
“Most of the Big Sioux River, we are looking at a greater than 50% chance of reaching major flood levels,” Gillispie said.
Flooding on that scale usually impacts state and U.S. highways. Businesses and homes are also threatened at those levels.
We are no stranger to these early spring flood events. One year that comes to mind is 1997. This is what the river looked like just north of Sioux Falls.
“I would say right now at least as far as the snowpack goes we are probably pretty similar to 1997,” Gillispie said.
Predicting the actual severity of the flooding involves a complex set of factors. All the rain forecast Wednesday and Thursday will be added to the current snowpack. The rate of melting will help determine what areas start flooding first.
The results of the immediate heavy rainfall will likely be felt across northwest Iowa.
“I think right now the only areas that have much of a flood threat over the next five days would be in NW Iowa, the Little Sioux, Rock, and Floyd Rivers,” Gillispie said.
And while warmer weather next week may sound like good news, it’s bad news for the spring runoff and would likely accelerate the timetable for flood threats farther north.