Without at least one heavy, warm rainfall of more than 2 inches, St. John River Valley residents near the St. John and Fish rivers shouldn’t see any significant flooding this spring, U.S. Geological Survey officials said this week.
Two hydrological surveyors have found that with this year’s snowfall about average — 110 inches — chances for flooding like that which devastated Fort Kent last year are rather remote. They have been measuring snowpack density, river depth and flow, and river ice depth around northern Maine weekly since March 1.
“A 2-inch rainstorm wouldn’t cause any significant flooding. Most of it [rainwater] would just be stored in the snow,” said Greg Stewart, data section chief for the U.S. Geological Survey’s Maine Water Science Center of Augusta, who is overseeing the surveying effort.
Nor were there any noticeable ice jams on the Fish and St. John rivers, said Andy Cloutier, a Geological Survey hydrologic technician, who, with fellow hydrologic tech Mark Huard, has been doing the weekly surveys.
“On the St. John and in that area, typically in the last five or 10 years, there were a lot of ice jams. There weren’t any noticeable as of now,” Cloutier said Thursday. “Things can change a lot, because there is still 2 feet of thickness of ice on the St. John, but things in March have been working to our advantage so far because there’s been warm days and cold nights and there’s no snowpack on the ice.”
In late April 2008, the St. John and Fish rivers in Fort Kent reached record levels, causing extreme flooding — closing off roads, shutting down the international bridge between Maine and New Brunswick and causing the evacuation of hundreds of people.
It took months, and millions of dollars, to repair the flooding damage, which also hit parts of upper Penobscot County.
The technicians measure the Allagash, Aroostook, Fish, Seboeis and St. John rivers — plus the north branch of the Penobscot River in Grindstone and the Penobscot in West Enfield — in Aroostook and Penobscot counties, Stewart said. They have found average conditions so far, he said Thursday. Near the St. John River, they found snowpacks of 24 to 36 inches, or snow that when melted would add 7 to 10 inches of water to the river and its tributaries.
“Last year it was more like 14 inches of water,” Stewart said.
They also found that snowpacks near the St. John were about 25 percent to 30 percent saturated, said Mark Turner, a service hydrologist with the National Weather Service in Caribou. About 181 inches of snow had fallen last year, compared with the 110 inches that have fallen this year with snowpacks 25 percent to 30 percent saturated, at this point both last year and this, he said.
“The critical measurement is when it gets to 30 or 40 percent. That’s when we consider it ripe. Once it’s ripe, it’s ready to go. Anything that goes into the top is going to come right out the bottom,” Turner said.
Snowpack saturation, ice jams and especially warm rains, which speed the melting of snow, are leading causes of flooding, the experts said.
“The temperature, timing and intensity of that rainstorm is important as well,” Stewart said. “You can get a 3-inch rainstorm over 12 hours that would produce a much higher flow than a 3-inch rainstorm over three days, and the ability to transform snow into water is increased with the temperature of that rainfall.
“A 50-degree raindrop will have a lot more energy to melt snow and transport it into the river than a 40-degree raindrop,” he added.
March’s lack of significant snowfall and gradually rising temperatures have kept away the floodwaters. Only in coastal areas, Augusta, Bucksport, Ellsworth and in York and Cumberland counties has snowpack density reached as high as 35 percent saturation — a sign that those areas will flood first if heavy rains come, Turner said.
Thankfully, no heavy rains are on the horizon.
As April dawns, the hydrologists will be watching river heights for signs that ice jams are coming, Stewart said. Ice jams can cause flooding when river water levels rise enough to cause ice to displace water.
“There is nothing you can do to prevent flooding. What we are trying to do now is understand what the flood potential is,” he said.