Snow survey under way to gauge flooding

The U.S. Coast Guard cutter Bridle breaks ice in the Kennebec River, Friday, Jan. 29, 2010, in Richmond, Maine. The Coast Guard is breaking ice to help lessen the chances of winter flooding. An ice jam roughly a mile long and 10 to 15 feet high remains in place downstream from Hallowell.(AP Photo/Robert F. Bukaty)
AP
The U.S. Coast Guard cutter Bridle breaks ice in the Kennebec River, Friday, Jan. 29, 2010, in Richmond, Maine. The Coast Guard is breaking ice to help lessen the chances of winter flooding. An ice jam roughly a mile long and 10 to 15 feet high remains in place downstream from Hallowell.(AP Photo/Robert F. Bukaty)
By Julia Bayly, BDN Staff
Posted Feb. 11, 2010, at 8:37 p.m.

FORT KENT, Maine — Thanks in no small part to round-the-clock weather coverage, it’s a safe bet people in Maine know down to the inch how much snow has fallen in the nation’s capital this week.

As for how much of the white stuff is on the ground in their home state, however, that’s something perhaps best left to the experts.

Measuring the annual snowpack is the job of members of the Maine Cooperative Snow Survey headed up by the Maine Geological Survey.

“The data gives us some good flood prediction ideas,” Robert Johnston, senior geologist with Maine Geological Survey, said Thursday. “Some of the co-operators are owners of dams and hydroelectric companies, and they use that information to predict when they should hold or release water on the rivers.”

A total of 110 sites around the state are measured during the surveys, and each site has been sampled once in January and once this month.

“So far the data shows that there has been slightly more snow than last year,” Johnston said, adding he expects February’s numbers to show a decrease in snow around the state except in Aroostook and Washington counties, which recently received about 10 inches of snow.

The highest snow total, Johnston said, was recorded in Fort Kent with 24 inches versus just 2½ inches measured in Bucksport. Compare that to the 3 feet of snow Washington, D.C., received this week.

By measuring the depth and mass of snow at a given location, Johnston said, his department can then determine the equivalent inches of water trapped in the snowpack.

In this case the snow in Fort Kent is holding a little more than 5 inches of water while the Bucksport snow is carrying a bit less than an inch.

“When snow falls there is generally 1 inch of water content to every foot of snow,” Johnston said. “As the snow compacts, that can change, [and] as we get closer to spring the snow becomes more dense holding more water.”

In addition to employees with the Maine Geological Survey, samples are collected by National Weather Service employees, Allagash Wilderness Waterway employees and members of the Maine Forest Service around the state.

According to Johnston, the ideal site is a south-facing slope in an open, hardwood grove, about 1 to 2 acres in size.

He takes 10 samples at each site, walking about one-quarter of a mile, to get a good snapshot of snow cover in the area.

“Some people are using high-tech aluminum measuring devices,” Johnston said. “Others prefer simple plastic pipes with a basic scale.”

March is the critical month for snow surveys, Johnston said, and surveyors will be out collecting weekly at that point.

“We are more apt to see warmer weather and melting snow in March,” he said. “The surveys help give us a better picture of what’s out there.”

Once that snow melts, all that trapped water has to go somewhere and rivers and lakes around the state begin to rise. A lot of snow coupled with a rapid melt rate can spell flooding problems.

Currently Johnston and his crew are keeping a close eye on the Kennebec River above the Gardiner bridge.

“A lot of the snow they did have there before the state got the heavy rains [late in January] is now locked up in the ice on the river,” he said. “Above the Gardiner bridge about two to three miles there is an ice jam we are worried about.”

The first measuring session this year took place Jan. 5 after a major weekend storm with 77 sites reporting across the state and along the New Hampshire border.

In Maine, the maximum snow depth was 29 inches with water content of 5.4 inches at Knowles Corner in Aroostook County. The minimum amount of snow measured in Maine was in Falmouth in Cumberland County with 6.4 inches of snow with water content of 1 inch.

The collected data are used to determine the potential for spring flooding by the River Flow Advisory Commission.

For information on how the survey is compiled go to www.maine.gov/doc/nrimc/mgs/explore/hazards/flood/sites/feb97.htm. For snow survey data, go to www.maine.gov/rfac/rfac_snow.shtml

http://bangordailynews.com/2010/02/11/news/bangor/snow-survey-under-way-to-gauge-flooding/ printed on July 30, 2014