Experts set to survey potential flood, ice jam threats in Maine

In this January 2014 file photo, chunks of ice reach near the top of bridges and walkways that stretch over the Kenduskeag Stream.
Brian Feulner | BDN
In this January 2014 file photo, chunks of ice reach near the top of bridges and walkways that stretch over the Kenduskeag Stream. Buy Photo
By Julia Bayly, BDN Staff
Posted Feb. 22, 2014, at 1:40 p.m.

FORT KENT, Maine – Given this winter’s cold snaps and snowstorms, it’s understandable if Mainers have visions of gardening and cookouts in their heads as they countdown the days until spring.

They are not alone. The National Weather Service and the Maine River Flow Advisory Commission are also looking ahead, but their focus is on potential flood and ice jam threats.

There are no big surprises in the snowpack or river levels around the state, according to a report released last week by the National Weather Service, and the potential for flooding due to ice jams or snowmelt is near normal for the short term.

But, as any river or weather watcher knows, that can change quickly.

“Historically, we do our big survey the first week in March,” Gregory Stewart, data section chief with the Maine office of the USGS and member of the river flow advisory commission, said late last week. “Right now, we are adding additional test runs to vet our sites and to make sure our observers are getting the proper readings.”

Stewart said his office will begin serious data-gathering March 1 and share that information with the entire river flow commission at its March 6 meeting.

“We go over snow maps, ice conditions and what concerns there may be with the weather outlooks for the following weeks,” he said. “At the moment, we are expecting to have normal to above normal readings.”

On Thursday, the National Weather Service offices in Gray and Caribou released the latest snowpack and flood potential forecasts as normal.

According to those reports, the snowpack around the state range from a foot to 3 feet along the coast, central highlands and northern Maine. Some areas of interior Maine have as much as 40-inches of snow-depth.

The readings, according to the report, are normal for the northern tier of the state and above normal in the south.

For now, all the moisture in that snow — the equivalent of 8- to 10-inches in some locations — is frozen. But once the weather turns warm, the moisture will be looking for a place to go.

“When the snowpack starts to turn around March, that’s when we start to see snowmelt driven runoff,” Stewart said. “Then we can look at the flooding potential.”

With the cold temperatures, he said, the snow acts like a giant sponge, so when it rains, the moisture stays in the snow.

“You don’t see any runoff because the snow absorbs the rain,” Stewart said. “But when that snow begins to ‘ripen’ and basically starts to melt, each raindrop turns into a drop and a half because it starts bringing the melting snow with it as it runs off.”

At the same time, he said, the ground begins to get saturated, and all water starts flowing. That opens the door for possible flooding.

The recent cold temperatures and snowy weather, according to the National Weather Service report, have translated to minimal runoff, but soil moisture around the state is up due to the January thaw and accompanying rains.

The report also indicates ice along northern, central and Down East waterways continues to strengthen.

The ice in the St. John River — which experienced its earliest freeze in 20 years — is estimated to be between 18 and 30 inches in places.

Thickness in rivers such as the Penobscot, Piscataquis and Mattawamkeag are estimated at around a foot. With colder conditions coming back into Maine, the ice is expected to thicken.

Ice jams are reported by the National Weather Service along the St. John River upstream of Fort Kent, the east branch of the Penobscot downstream of Grindstone, the Penobscot near Winn, the Piscataquis upstream of Howland and in the Kenduskeag in Bangor.

While they are not expected to move or let go anytime soon, Stewart said ice jams are notoriously unpredictable.

“Ice jams happen earlier in the year when that snowpack is not ripe,” he said. “They are very dynamic, and you really have to pay attention to them when the ice does start to move.”

Rapidly moving ice can quickly pile up, causing rivers to rise dramatically behind it, he said.

“We always worry about ice jam flooding early on and all winter,” Stewart said. “It is something we monitor all winter.”

For now, weather watchers around the state will keep an eye on Maine’s rivers and waterways as the spring thaws approach.

“At our March 6 meeting, we will have a pretty good idea of where the areas of concern are we should be watching,” Stewart said.

 

http://bangordailynews.com/2014/02/22/news/state/maine-river-flow-advisory-commission-focuses-on-potential-flood-ice-jam-threats/ printed on August 30, 2014