The freshet is at hand
If you live near a river, you’re always on alert at this time of the year. And this year is particularly concerning, since we entered the final week of March with a good 10 inches of water sitting on the ground, in the form of a still-deep snowpack. And knowing it’ll all be gone in a month certainly warrants concern.
In fact, the Spring Flood Outlook, issued by the National Weather Service in Caribou, indicates that the risk for general river flooding, and ice jam flooding is “well above normal.”
One way to think about the soon-to-be meltwater is that 10 inches is about a quarter of the average TOTAL annual precipitation here in Aroostook County.
Of course the flood everyone remembers is the Valley flood 11 years ago, in late April of 2008. One way to measure the degree to which a flood stands out is to compare the river gauge maximum with other floods at the same gauge site.
Below, are the top five crests of the Saint John River at Fort Kent. Note how places two through five are tightly clustered, but number one on the list stands, statistically, head-and-shoulders higher.
(1) 27.74 ft on 04/30/2008
(2) 24.94 ft on 04/30/1979
(3) 24.59 ft on 05/01/1974
(4) 24.25 ft on 04/17/1994
(5) 23.99 ft on 04/19/1983
The ’08 flood was nearly 3 feet higher than second place. Three feet may not seem like a lot, but visualize water going up, and also spreading out. Three feet is a pretty big deal.
You can obtain river gauge on the home page of the NWS Caribou office (weather.gov/car). Above the map of Maine are different choices in blue text. Choose “Rivers and Lakes.” That will give you a map of dots, representing river gauge sites. There are two near Fort Kent. The Fish River is the lower green dot, while the Saint John is the upper green dot. Click on it. Then scroll down and, on the left, you will see the top five crests, and, below that, specific flood impact information.
An example from the Saint John gauge at Fort Kent says, “26.7 – Widespread flooding of lower East Main Street inundating several structures in the center of town. Water flowing over the top of the Fish River bridge. Evacuations probable.”
All of the information I have described above is given for all of the gauge sites. You’ll note there are two for the Aroostook, one in Masardis and one in Washburn.
Meanwhile, we are two weeks away from the 25th anniversary of the Fort Fairfield ice jam flood. I spoke to a gentleman some years ago who told me that he tried to get some inventory out of his shop in the midst of the flood, and that the waist-deep icy water just pinned him to a wall, and he thought he was done for. A number of people were kind enough to respond to my request for any recollections from the flood, and their recollections can be found at facebook.com/tedsweather.
Tragically, the ’94 flood claimed two lives. From the New Brunswick Environment and Local Government website: “Shortly after 10 pm, April 16, a sudden release of water from an ice jam on the Aroostook River drowned two customs officers approximately one kilometre east of the Maine border. The men were traveling along a low lying section of Tinker Road, located along the south side of the Aroostook River, when it was suddenly inundated by fast rising floodwaters from the broken ice jam. The moving water and ice pushed the vehicle part way into the ditch, eventually submerging it in approximately 0.6 metres of water. The victims left the vehicle in an attempt to reach shore. A third man survived by remaining on top of the submerged vehicle for 45 minutes until rescued by a search team in a boat.”
Ice jams are unpredictable, and can occur during the spring river ice break-up in any season. Meltwater flows into the rivers and lifts and breaks the ice from below. Sometimes the ice can get jammed and block a river channel in such a way as to cause water to back up behind the jam. Sometimes the water will seek a different route. Also, when an ice jam releases, water levels rise rapidly downstream.
Ice jams are not limited to larger rivers. There is a video I show in my presentations where a tiny mountain stream, along which people are hiking, suddenly becomes a roaring torrent, with the only clue having been the loud noise approaching. These people knew what the sound was, and climbed to safety in the nick of time. Google “Felchner Brook flood.” You won’t believe it.
In terms of major non-ice-jam floods, such as the one which struck the Saint John Valley in 2008, they don’t happen unless you get an added ingredient while the snow is melting, and that is heavy rain. Even though the winter of 2007-2008 was the record winter for snowfall in northern Maine, flooding of the magnitude seen would not have occurred had not a heavy rainstorm dumped 2-3 inches of rain, region-wide toward the end of April.
So major river flooding, which affects all communities along a river, does not happen from snowmelt alone. But if you have a big rainstorm, over a large area, that is concurrent with snowmelt, look out.
Ted Shapiro holds the Broadcast Seal of Approval from both the American Meteorological Society and the National Weather Association. An Alexandria, Va. native, he has been chief meteorologist at WAGM-TV since 2006. Email him at firstname.lastname@example.org.