Snow depths deeper but flooding odds drop

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John M. Steiner / The Sun Bob Martin, Pipestem Dam manager, measures the snow depth Thursday. The measurements help gauge moisture content and assist with spring flooding predictions, which lately indicate reduced chances of flooding on the James River.

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Despite some additional snow and moisture, the outlook for flooding in the James River basin remains low.

“At this point I’m liking what I see,” said Allen Schlag, hydrologist with the National Weather Service in Bismarck. “I don’t see any real reason to consider reaching for the panic button.”

Current forecasts indicate less than a 5 percent chance of flooding of any type at Grace City in the northern basin and at LaMoure in the southern basin. This is a decrease from a 10 percent flooding probability at Grace City two weeks ago.

Pipestem Creek at Pingree now shows a 7 percent chance of flooding compared to an 11 percent chance of flooding forecast two weeks ago.

The decreased likelihood of flooding comes despite increases in snow depths and moisture content. This is in part due to the fact the calculations used to forecast flooding are written with the expectation of more moisture in the snow as the spring progresses. The snowfall accumulated since the last forecast hasn’t been enough to increase or even maintain the probability of a flood.

Bob Martin, dam manager at Pipestem Dam, said the snow depth had increased from 10.8 inches to 15.2 inches in the last two weeks. The moisture content in the snow increased from 1.79 inches to 2.13 inches in the same period.

“It is really not at levels of concern,” Martin said. “For one thing, the fall was very dry. Our soil probes at 1 foot and 2 feet are reading as dry as they will read. A lot of the moisture in the snow will soak in.”

Schlag said the potholes of the region are another factor.

“The potholes are still higher than historical levels,” he said. “But they are lower than some of the previous years. That means we have a little more storage in the countryside.”

However, Schlag cautions that overland flooding is still possible.

“There is still a concern with overland flooding especially south of Jamestown,” he said. “That possibility would be controlled a great deal by the amount of rain on top of the snow pack this spring.”

The current long range forecasts from the NWS have equal chances of above- or below-normal precipitation for the three-month period.

“There is nothing really stark in the forecast,” he said. “There are no big climate indicators we can see that would mean big spring rains.”

This is also contributing to lower chances of floods.

The current snow pack levels are giving officials some chances to manage the rivers and dams more efficiently.

“The 2 inches of water on the ground this time of year is not alarming,” Schlag said. “But it means we could see adequate flows through the rivers this spring.”

Martin said the levels of flows may allow the Pipestem Dam to be managed to promote crappie reproduction.

“If we can, we plan to not drop the Pipestem Dam levels in May to allow the crappie to spawn,” he said.

He said the dam’s outflows would be managed to match inflows to keep the reservoir level steady while the fish spawn. This increases the spawning success.

Currently, Pipestem Dam is releasing 2 cubic feet per second to match inflows from springs and keep the reservoir level steady. No water is being released from Jamestown Dam.

Sun reporter Keith Norman can be reached at 701-952-8452 or by email at knorman@jamestownsun.com

Tags: local news, news, flood