Kenai Peninsula officials were keeping a close eye on quickly rising water levels at the Soldotna bridge on Friday. Eric Mohrmann, the borough's director of the Office of Emergency Management warned that a possible water surge could occur if the ice jam broke. "Persons living in low lying areas downstream of the bridge, such as Poacher's Cove and Big Eddy, should be alert to a possible rapid rise in the river water level," he wrote in a press release.
The potential flood appeared to be the result of ice jams between the bridge and Big Eddy area, Mohrmann told the Daily News. "The water in the river is always flowing," he said. "When the temperature drops, ice flows downstream and establishes a jam. The water builds up behind it and eventually finds a channel out."
Area temperatures have ranged between 10 and 14 below, he said.
Old-timers may remember similar conditions that culminated in the biggest flood in the recorded history of the Lower Kenai River.
On Jan. 18, 1969, temperatures had dropped to 25 below and a massive ice jam formed in a flat, wide spot known as Falling In Hole. The problem was exacerbated by a "jokulhlaup" -- or glacial gush. A lake had built up behind Skilak Glacier, about halfway between Seward and Skilak Lake. As the temperature dropped, the glacier cracked and the lake emptied like water pouring out of a giant bathtub.
The river stage at Soldotna hit 22.62 feet, the highest ever recorded. Witnesses at the Sterling Highway bridge in Soldotna reported ice chunks the size of trucks racing downstream at 42 knots. The press of ice and water sheered buildings off their foundations. Ninety people had to leave their homes. Thirteen homes were reported lost or damaged along with "countless docks and floatplanes," according to press reports. It took several days before warming temperatures and rising water pressure broke the dam and eased the flooding.
The lake behind Skilak Glacier burst out every two or three years, usually in colder months. Another such event sent the river stage at Soldotna to 20 feet on Jan. 28, 2009.
The Snow River Glacier Dam Lake, east of Moose Pass, discharges with similar frequency. But these Alaskan jokulhlaups seldom cause much damage.
The 1969 flood may have been the biggest and most dramatic. But, because of development, the flood of October and November 1995 proved much more costly.
That flood was caused not by an ice jam, but by heavy rains that caused flooding across the Peninsula. On the Lower Kenai it was a "100-year flood," that is the type of flood that federal authorities say occurs only once in a century.
Big Eddy was ground zero. The low land in the middle of the giant oxbow bend had been heavily built on since 1969, with houses and gravel roads in what had previously been absorbent wetland. It was reported afterward that "dozens" of homes had been erected near the river without permits and that the maps indicating floodplains may have been out of date.
The river surged across the neck for a week, leaving a junkyard of metal roofing, trailers, boats, furniture and other debris.
Borough officials said 66 primary residences and 309 recreational cabins were damaged. For the most part, the damage was limited to the great mess left behind by receding waters; only a couple of homes were said to have lost most of their value. But many public facilities were compromised and officials estimated total losses at $10 million.
One bright spot in the 1995 flood was the discovery that bank restoration efforts -- which some at the time considered junk science or, at best, theoretical -- actually worked. Most riverbanks left in their natural, grassy condition fared well while gravel washed away and rock jetties accelerated the current, undermining both themselves and adjacent banks. The newly-planted willows at Soldotna Creek Park bent with the current, slowed the waters and their roots held the soil.
The present situation is probably not as serious as those floods, said Mohrmann before heading for the Soldotna bridge to take another reading on Friday afternoon. "But it's hard to tell, really."
Reach Mike Dunham at email@example.com or 257-4332.
By MIKE DUNHAM
Anchorage Daily News