Ice jams up Kenai River
Minor flooding expected to occur in Big Eddy area
Blocks of ice fan out along the banks of the Kenai River beneath the Warren Ames Memorial Bridge Wednesday afternoon. Officials from the National Weather Service are advising that ice formations and increasing water levels may cause minor flooding along the river.
Photo by M. Scott Moon
It's finally been cold enough to freeze the most popular river in the northern hemisphere and nearly bring it to a halt. Though it's slowing down and freezing, the Kenai River is still dangerously active.
John Mohorcich, Kenai River Center manager, received phone calls early this week through the Kenai Peninsula Borough Office of Emergency Management regarding the swiftly rising river.
"I went out Monday to check out the river. I found that the channel around Big Eddy was choked with ice. The water level is up to its ordinary high water stage, and the ice was packing in," Mohorcich said.
"What happens is frazil ice (tiny ice chunks formed in supercooled air and turbulence) collects and creates a plug and jam area. Then it will worm its way through the river. I usually takes some time," he said.
Though, as the National Weather Service reported Wednesday, this has only taken 30 hours. The statement for the Kenai River reported water levels at the Sterling Highway bridge rose rapidly, "approximately 4 feet over the last 30 hours due to freeze-up ice jamming on the river."
The river was reported full of ice and rising on Monday at Eddy Lane in the Big Eddy area. Mohorcich said the ice jam was as far up as Poacher's Cove, while the freeze-up process works its way upstream. John Czarnezki, resource planner, for the Kenai Peninsula Borough has been keeping his eyes on the river for the duration of the freeze. His latest report was the river was about a foot above the normal high water line, which is still two feet below full bank.
"Some areas have open spaces, and new ice is forming at Swiftwater. Though it varies from point to point, there is still a fair amount to go until anything gets to bank level," Czarnezki said. "So far, so good."
David Streubel, hydrologist with the National Resource Conservation Service ( NRCS), said there are usually no problems with the freeze-up, but he has experienced otherwise.
"When it's really cold like this, we get a lot of frazil ice that gets suspended in a column of water. Then the water will basically cut off the channel in a cross section. Sometimes it happens where the whole ice sheet will shift," Streubel said.
"I've seen it where all the sudden the water will get pinched off and the ice will release. Then water can flow on top of the ice and freeze wherever it goes, including out of the bank."
Streubel said the basic freezing of the river occurs in two phases, provided the conditions are right. The first is when ice frazil is formed and moves down river, growing all the while. Scott Lindsey, NRCS hydrologist, said as frazil moves down stream, it forms ice-pans that grow bigger and bigger. These keep moving until they cannot move any longer and enter the second phase.
"This is where you see the backward motion of the process, as the river gets clogged with ice, it backs up, slows the river's current and eventually freezes the entire top," Lindsey said.
Streubel said as water passes under the ice, the height of the river will go up, which accounts for the rise in the river level.
"Each river has its own characteristics, down there from Big Eddy up to tidal influence, there have been problems with big ice jams before as it freezes from the mouth up. Some years the freeze goes all the way up to the Kenai Keys," he said.
Bill Berkhahn, district ranger for Alaska State Parks, pays close attention to the river, since the river is a state park. He said the river will stay frozen and the freeze will level out over time.
"Once everything freezes, it will stay frozen until breakup — unless it starts raining like it did earlier," he said.
The National Weather Service statement said the current cold snap will persist through Thursday, then temperatures are expected to rise as "more seasonable temperatures are expected through the weekend."
The report added that the freezing process will continue slowly and levels are expected to stabilize near bank-full levels. Increases in water level may cause minor flooding and damage from ice movement. Owners of riverside structures such as docks, landings or bank side staircases should take precautions to protect property from damage.