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Ice dam break suspected as cause of Rabbit Creek flooding

Casey Grove
Rabbit Creek, below the lake, mud on snow and ice indicate water level was significantly higher earlier in the event, Friday, June 14, 2013.
Scott Lindsey
Marc Lester / Anchorage Daily News Rabbit Creek floods the area around 140th Avenue near Buffalo Street on Friday afternoon, June 14, 2013. Road crews work to clear debris from culverts.
Marc Lester
Potter Marsh from air shows muddy water flowing from Rabbit Creek Friday, June 14, 2013.
Scott Lindsey
The outlet of Rabbit Lake shows that lake level was higher and has dropped significantly Friday, June 14, 2013.
Scott Lindsey
Rabbit Creek, below the lake, mud on snow and ice indicate water level was significantly higher earlier in the event, Friday, June 14, 2013.
Scott Lindsey
Marc Lester / Anchorage Daily News Rabbit Creek floods the area around 140th Avenue near Buffalo Street on Friday afternoon, June 14, 2013. Road crews work to clear debris from culverts.
Marc Lester
Potter Marsh from air shows muddy water flowing from Rabbit Creek Friday, June 14, 2013.
Scott Lindsey
The outlet of Rabbit Lake shows that lake level was higher and has dropped significantly Friday, June 14, 2013.
Scott Lindsey

Rabbit Creek jumped its banks Friday morning on the Anchorage Hillside, sweeping down trees, washing out a road and prompting police to knock on doors warning of possible evacuations.

Hydrologists think an ice dam broke suddenly at the creek's outlet from Rabbit Lake in the Chugach Mountains, draining thousands of gallons per second.

The flash flood apparently caused no injuries and did not require any evacuations, police said. Clogged culverts under East 140th Avenue at Buffalo Street caused water to flow over the roadway, tearing off chunks of the embankment on the downstream side. The foundation of at least one house was damaged, police said, but it was too early Friday to know the flood's full impact.

Hank and Ronnie Elias are retirees who have lived along the usually clear waterway off Old Rabbit Creek Road for 35 years. They could hear boulders tumbling down the creek bottom between 8 and 9 a.m.

"That's what woke us up," Hank said while standing on his deck, raising his voice over the din of the clattering rocks and rushing water only a few feet away. "They've been rolling and rolling and rolling."

A log jam diverted the now-muddy creek water onto their property. It was about foot to two feet deep and running all around their A-frame house, Hank said. They called city officials but were told the neighborhood is outside a road service area and not the city's responsibility.

"They said, 'We don't have anything to do with any of that property up there. I said, 'But I pay property taxes. High property taxes,' " Hank said. "We needed at least some heavy equipment to bust up the logs. If nothing else, a stick of dynamite."

If it had not been for their neighbor, Dave Piaskowski, borrowing a backhoe to move the debris, they would have been in "deep bleep," Hank said.

"He's what saved our house and his house," Ronnie said.

A police officer came by at one point and said they might have to leave. The Eliases already had a "bailout bag" packed with medication and other essentials in case they had to evacuate. Hank said he would stay unless the foundation started to shift.

The couple will have to move their house away from the creek, Hank said. They'll also have to treat or boil well water, he said.

"If it had kept going the way it was going, we could have lost everything," Ronnie said.

Clearing logjams, at least the literal kind, in such situations is not the job of the city, said Kevin Spillers, director of the Office of Emergency Management. Spillers had been monitoring the flooding and did not see any imminent, life-threatening danger, he said.

"There are homeowners who have their idea on a specific course of action they think the city should take, but that doesn't always equal sanity," Spillers said. "I think everybody did pretty much what they can. I can understand an individual homeowner's concern, but these are things they're going to need to take up with their insurance claim."

Just upstream from the Eliases there were also worries about losing property but of a somewhat lower dollar value.

Another neighbor, Kelly McGovern, said two kegs full of beer chilling in the creek were tied off and bobbing in the rushing waterway when he came home from work.

"I rescued the kegs. I put on a harness and a life vest and put a line out to the tree. It was Midnight Sun Sockeye Red (IPA), so I had to do that," McGovern said. "I've been here 25 years and it's never come close to that volume. Some big anomaly happened."

Officers went to at least three houses in the area about 11 a.m., police spokeswoman Dani Myren said. About an hour later, a police sergeant at the creek said the water was dropping and evacuations appeared unnecessary, Myren said.

At 140th Avenue and Buffalo Street, just south of DeArmoun Road, the washed-out avenue remained closed into the afternoon. City workers used an excavator to move huge piles of sticks and logs out of the culverts while utility workers sawed trees leaning close to electric lines nearby. One worker told a neighborhood resident the road would be closed until at least Saturday so repairs could be made.

Warm weather in recent days has increased the melting of mountain snow, swelling waterways all over Southcentral. That is expected to intensify this weekend with temperatures rising into the 80s, National Weather Service forecasters say.

But something out of the ordinary happened at Rabbit Creek, according to weather service river watchers. Not since 1977 had as much water poured down the drainage that fast, hydrologist Scott Lindsey said.

"That area's probably a lot more built up since then," Lindsey said.

In that flood, an ice dam burst at Rabbit Lake, and the hydrologists suspected the same cause for the flood Friday. Lindsey flew in an Army National Guard UH-60 Black Hawk helicopter on a scheduled training flight Friday to investigate the sudden surge of water.

They found brown snow at the outlet from the lake, evidence of a heavy, muddy outpouring, Lindsey said. The top of the lake was still frozen but the ice cover slumped down like a pushed-down trampoline because the water underneath rushed out, he said.

"At the outlet of the lake into the creek, there was a lot of snow where the channel cut through it," Lindsey said. "So it looks like, somehow, either the ice built up at that outlet or the snow was enough to block it. But several feet of lake level drained off in a big hurry."

There were obvious signs, even from the air, of erosion and undercut trees on the creek's edges running its entire length, Lindsey said. At its end, the floodwater turned much of Potter Marsh an unfamiliar brown color.

The U.S. Geological Survey calculated that the 1977 event dumped about 400 cubic feet of water per second into Rabbit Creek, Lindsey said. That's fast enough to fill an Olympic-sized swimming pool in less than four minutes. It's still too soon to know the flow rate of the flood Friday, Lindsey said.

Of the other drainages in the Anchorage Bowl, Ship Creek had been the closest to flooding on Friday, said Dave Streubel, another hydrologist, earlier in the day. By afternoon, Ship Creek and most area creeks were lower, Lindsey said.

Because Rabbit Creek so rarely floods, it does not have gauges to remotely measure its level like the others, Lindsey said.

"I'm sure there'll be folks wondering why there was no warning about this happening. And the problem is there's no monitoring of the lake or the stream. An event like this is rare enough that I don't think most people would even remember it happened in 1977. It's unfortunate but it's something very difficult to predict."

It certainly was not something Hank and Ronnie Elias saw coming, they said. The creek is normally very peaceful and flows by slowly, and bears, moose and other wildlife wander through often, they said.

"We love it out here," Ronnie said.

"It's the closest to Alaska you can get while still living in Anchorage," Hank added.

 

Reach Casey Grove at casey.grove@adn.com or 257-4589.

 

Hank Elias, who's lived with his wife, Ronnie, alongside Rabbit Creek for 35 years described a flash flood Friday, June 14, 2013 that cut away several feet of the bank next to his house. (Video by Casey Grove/Anchorage Daily News)

 


By CASEY GROVE
casey.grove@adn.com