FAIRBANKS -- The way Rocky Reifenstuhl sees it, there are two types of river crossings in Alaska.

"Type one is you're going to walk across, and type two is the kind you know you are going to be swimming across the river," said Reifenstuhl, who has walked or swam across dozens of rivers and streams during 30-plus years as a geologist and wilderness trekker in Alaska. "Type one can turn into type two real fast."

When that happens, you have to be prepared, said Jim Lokken, another wilderness-savvy racer and veteran of many a river crossing.

"The problem is people freeze," Lokken said. "They need footing every step so they're out in the middle of the river not moving and they get swept off their feet. Then, they're trying to get back on their feet, trying to stand up, and it never works."

Once you are swept off your feet, there is only one thing to do, he said.

"What you need to be doing is hammering as hard as you can for the other side," Lokken said.

The Swiss woman who drowned Aug. 14 trying to cross the swollen Teklanika River on the Stampede Trail north of Healy never had that chance.

Claire Jane Ackermann, 29, had tied herself to a rope that other hikers had previously strung across the stream. There was too much slack in the rope and the current swept Ackermann and a 28-year-old unidentified Frenchman off their feet, at which point they were submerged and held underwater by the current.

The Frenchman told Alaska State Troopers he was able to cut himself free from the main line and make his way to the bank, where he dropped his backpack. When he turned back around, Ackermann was submerged, still attached to the main rope.

The French hiker managed to make his way back to Ackermann and cut her loose from the main line, but by the time he floated her a half-mile downstream and was able to reach the shore, Ackermann was dead.

Ackermann's drowning highlighted what is one of the biggest dangers of traveling in wilderness Alaska -- crossing cold, strong, glacial-fed rivers.

"For me, crossing a river, a type two river in Alaska, is one of the most dangerous things anybody can do and requires the utmost respect and consideration before you do it," said Reifenstuhl, whose background as a geologist helps him understand the hydrology of rivers better than most people. "There's nothing more dangerous out in the wild, particularly in Alaska, than fast, moving water.

"I'd much rather be confronted by grizzly. If you think a grizzly is strong, water is a thousand times stronger. Water is not doing a bluff charge, it's just going downstream. If you're in the way, you're going downstream too."

Crossing considerations

Several factors go into picking the right place to cross, including water depth, strength of the current and runout.

How deep is too deep when it comes to fording a stream and staying upright?

"If you've got something with some strong current, you don't want to get any deeper than your crotch," said Bob Groseclose of Fairbanks, a 61-year-old veteran of several Alaska Mountain Wilderness Classic races.

Several signs can help determine current strength.

"If you can hear rocks flowing downstream, you don't even mess with it, you're in the wrong place," said Mark Ross of Fairbanks, a veteran of the Hot Springs 100 and Alaska Mountain Wilderness Classic wilderness races.

Find a spot where the water braids into multiple channels, which are shallower and not as strong.

An important consideration when crossing a stream or river is what the runout, or the area below the crossing, looks like.

"So if you do lose your footing, where are you going to go?" Reifenstuhl said. "

Or as Lokken put it, "If you get to the far shore and the bank is bad, you're screwed."

Watch for hard-to-climb cut banks and strainers or sweepers, downed trees in the river that can trap you if you are swept off your feet and down the river. Never cross a stream or river just above a canyon or rapids where the current narrows and gets stronger.

Water levels in glacier streams fluctuate daily, depending on the weather. They come up late in the day as a result of ice melt and they go down at night when it cools off. The best time to cross is usually early in the morning.

"People cross a river and they think it's going to be the same when they come back and suddenly the water is higher and it's not the same river," said Ed Plumb of Fairbanks, who has crossed dozens of rivers and streams on backcountry trips.

Crossing techniques

Experts agree on one thing: Using a rope to cross a river is not a good idea and securing yourself to a rope like Ackermann did is a recipe for disaster.

"I would never tie myself to a rope," Plumb said. "If there was a rope all the way across the river and it was taut, I maybe would hold onto the rope, but never tie into it."

There are a few standard techniques used to cross rivers and streams, depending on the river and how many people are crossing.

Plumb and Groseclose use walking sticks, which Groseclose refers to as the "tripod" technique to cross rivers and streams.

"I get a stick and put it upstream of me," Groseclose said. "I'm facing straight into the current and side stepping and moving the stick as I go, leaning into it pretty stout."

Ross, who travels solo most times, said he doesn't use a stick and relies on the strength in his legs.

"Don't cross your legs. Keep a wide stance," said the 155-pound Ross, adding that he has never been swept off his feet. "Your legs are what's keeping you going. If you do anything to compromise the power of your legs, (the current) is going to blast your legs out of there."

That's likely what happened to Ackermann when she tied herself into the rope.

"She couldn't get her weight under her," Ross said.

The most important thing to do when crossing a river is to face upstream, Ross said.Linking arms with another person or persons to increase stability can help.

"You're taking one step at a time with the plan that if you go down it has to be every man for himself to survive," Reifenstuhl said.

Multiple hikers can also use the pyramid technique, or "geese formation," as Plumb called it. Form a V facing into the current and move sideways across the river to break the current.

"I've crossed a few times where I lost my footing and had to go for it" Lokken said, who always wear shoes. "When the gravel starts rolling underneath you and you get swept off your feet, you want to be going as fast as you can. You want to be able to run or bounce off the bottom, anything you have to do to get to the other side."

Frigid Water

Know how cold the water you're walking or diving into is.

"You need to be across that river in 60 seconds because your muscles are going to get cold and stop working," Reifenstuhl said. "Once you go into 40-degree water everything changes."

When he crosses a river he knows he may have to swim, Reifenstuhl puts all his gear in a plastic bag that goes in his backpack, which usually weighs less than 35 pounds. He ties the plastic bag shut, trying to preserve as much as air as possible in the bag so it acts like a floatation device.

"That acts as a life preserver on your back," he said.

When swimming across rivers, Reifenstuhl wears a thin layer under his rain gear, which he cinches down as tight as possible to provide some insulation against the cold.

After getting out of the water, he puts on a dry layer of clothes to warm up and gets moving as quick as possible.

"Plan to move fast," Reifenstuhl said.

One thing Groseclose makes sure to do before he crosses a stream or river is unclip the waist band on his backpack so he can shed it quickly.

The best way to cross a river is in a pack raft, said Plumb, an avid pack rafter.

Margin of safety

The scariest river crossing Reifenstuhl has ever encountered was on the upper Kongakut River in the n northeast Brooks Range three years ago on an eight-day, 270-mile hike from the Canadian border to the Dalton Highway with his brother, Steve.

Standing at the edge of the river, the Reifenstuhls could hear large boulders being dislodged and swept down the river.

"It was very, very fast, probably the fastest river I've ever crossed," Reifenstuhl said. "It was pretty swollen by rain. It was very silty. There were large cobbles (rocks rolling down). The bank on the other side was sandy cobble that was gong to be difficult to get out. There was nothing to hold onto."

The river was less than four feet deep but Reifenstuhl said the current was raging.

"We hooked arms, walked straight into the river and knew we were going to be get swept off our feet," Reifenstuhl said.

When that happened, the two brothers dove in and swam diagonally across the river.

"We were out of the river in 25 or 30 seconds but it seemed like an eternity," he said.

But Reifenstuhl points out that he and his brother spent 45 minutes looking for the safest spot to cross and talked about what they were going to do.