AUGUSTA, Maine — The combination of deep snow and extended cold snaps has upped the potential for spring flooding, members of the River Flow Advisory Commission concluded Thursday after assessing hydrologic conditions across Maine, as well as short-term weather forecasts.
Snow depths are dramatically above normal for this time of year in central and coastal areas, according to the National Weather Service. Portland, for example, has more than five times its normal snow depth, while Bangor has about seven times its usual amount on the ground and Machias has more than nine times normal snow depth.
“It’s sort of the opposite of where we usually are,” Maine Emergency Management Director Lynette Miller, the river flow panel’s co-chairman, said. “We actually have less snow on the ground and less water content in the ground in far northern Maine than we do in that sort of swath along the coast.”
Snow surveys conducted on Monday and Tuesday showed snowpack water content ranging from 5 to 8 inches across the state, with the largest amounts in a swath from the midcoast to the Down East, commission members noted.
“For the most part, many of the drivers of [flooding] risk are in the normal range. Ice conditions are in the normal range. Even snow packs across the headwaters of our major rivers are in the normal range,” Miller said. “Where we see a difference is a very large amount of snow that’s on the ground in the lower third of the state.”
Miller said weather forecasts call for cool weather and less than normal precipitation over the next two weeks, which will likely hold the snow in place.
“And the farther into the spring that we carry that amount of snow — and it’s really quite dramatic, especially in southern Maine — then the risk increases that it’s going to warm up and we have the possibility of rain events coming in,” she said.
“We came to the conclusion that the flood risk was elevated, which again doesn’t mean that for sure there’s going to be flooding but simply because of that large amount of snow that’s going to remain with us,” Miller said. “We’re carrying that risk forward at this time.”
The panel did not identify any particularly vulnerable major rivers Thursday.
“All the major rivers are really within normal range,” Miller said. “There’s a normal amount of river ice, normal free flows. All of those things that we look at are really within normal range. So it really is a question of how long is the snow going to stay with us and can we avoid any major rainstorms during the period of time when we still have ice and we still have a lot of snow on the ground.”
In the meantime, the U.S. Coast Guard is working with the weather service, MEMA, the USGS and other partners to monitor river ice conditions and plan for continued ice-breaking on the Penobscot and possibly Kennebec rivers. Along other rivers, areas prone to ice jams will be monitored as the spring progresses and reservoir storages in the headwaters of Maine’s large rivers are being drawn down to prepare for spring rains and runoff.
The full report of the March 5 meeting will be available online at maine.gov/rfac by late Friday afternoon.