Runoff could be a flood factor here
It is not the amount of snow on the ground of the James River basin but the frozen ground beneath it that has hydrologists at the National Weather Service concerned.
The NWS issued its January hydrological outlook on Friday. It will issue its first spring flood outlook on Feb. 25.
“There is always a risk of flooding,” said Alan Schlag, hydrologist with the National Weather Service in Bismarck. “We have about a normal snowpack but the risk of flooding is right around normal to a little elevated based on wet soil conditions.”
Schlag said current forecasts are preliminary with about six more weeks of snow accumulation expected. Current long-term forecasts are indicating cooler than normal temperatures and greater than normal precipitation.
“We’ve had a cold winter but we’ve had some breaks of warm weather,” he said. “That water has not soaked into the ground but created a layer of ice on the surface beneath the snow. That could increase the runoff that reaches streams when the snow starts melting.”
Frost depths are also being reported as deep as 26 inches, Schlag said, deeper than the normal amount of less than 20 inches. That can also increase the amount of runoff going into streams during the spring melt.
“The greatest risk is an early spring fast melt accompanied by a rain,” he said. “That moisture would have nowhere to go but into streams or possibly overland flooding.”
Calculations based on historical data place the chance of major flooding in the James River basin as being fairly low.
There is less than a 5 percent chance of major flooding of 18 feet — 4 feet above its flood stage of 14 feet — on the James River at LaMoure. There is also less than a 5 percent chance of major flooding of 13 feet — 4 feet above its flood stage of 9 feet — on Pipestem Creek at Pingree. The James River at Grace City has a 5 percent chance of reaching major flood stage of 15 feet — 3 feet above its flood stage of 12 feet.
Sun reporter Keith Norman can be reached at 701-952-8452 or by email at firstname.lastname@example.org