WHAT IS THE GORGE? This is a main source of conversation around Ennis during especially cold weather. Old timers have great stories of cows getting stuck out on ice flows in the middle of the river and the year the gorge took out the old Varney Bridge. I have been fascinated by this phenomenon ever since we moved to Ennis in 1993. It is awesome to witness and hard to understand. I interviewed some of the natives and hydrologists as well, trying to find out the cause. In the winter of 2010, Greg Lemon, Editor of The Madisonian, our local newspaper, wrote an article that pretty much describes what causes the Gorge.
Gorging on the Madison, a chilly phenomenon
By Greg Lemon, The Madisonian
View from the Ennis Bridge"It happens nearly every year. When the temperatures drop near zero and the wind howls mercilessly, the Madison River begins to freeze up. Around Ennis, when the Madison River will gorge becomes big topic of conversation.
“Have you seen the river?” someone will ask.
“Yeah. She’s froze up down by the lake,” will be the reply. “Betcha she gorges in by the end of the week.”
If you search the Internet for Madison River gorging, amongst the stories of big trout gulping salmon flies, you’re apt to find a variety of pictures and stories about ice choking the river around Ennis and pushing water out into nearby fields, overflow sloughs and pastures.
Along with the anticipation come the rumors and legends about the uniqueness of the Madison River ice jams. Some will say it’s the only river in North America to gorge this way. Some say it freezes from the bottom up because the wind blows so hard. But the fact is many rivers around southwest Montana freeze in a similar fashion, said William Locke, professor of environmental science at Montana State University in Bozeman. “It’s actually pretty common,” Locke said. Take for instance the Gallatin River, he said. The most common form of flooding on the lower Gallatin is the result of ice jamming.
However, the speed the ice on the Madison River and the depth the ice reaches is impressive, said Pat Clancey, fisheries biologist in Ennis. Every year Montana Fish, Wildlife and Parks close the Ennis and Valley Garden Fishing Access sites because of the ice gorging.
In a 1921 article in “Proceedings of the Society of Civil Engineers,” written by J.C. Stevens about the ice-jamming phenomenon on the Madison River.
“It has been stated by local authority that the Madison is the only river in Montana which overflows from ice gorges during cold weather. This statement is not true. The Ruby, Boulder, and many small streams behave exactly in the same manner as the Madison in this respect,” writes Stevens.
Some of the characteristics that contribute to the flooding and ice gorging are the shallowness of the river, the low river banks and the relatively steady flow of the water, Stevens wrote. The ice gorge itself comes from a mix of frazil and anchor ice, he wrote. Frazil ice is formed on turbulent rivers when the weather is cold enough to freeze surface water. It looks like shards or chunks of ice in the river. It’s also sometimes called slush ice or needle ice. Anchor ice is formed around rocks and cobbles in shallow water and is a result of “a rapid radiation of earth heat from the river bed into space,” writes Stevens. It forms most rapidly on dark-colored stones, during clear and cold nights.
Larry Love, who is an Ennis native and on the board of the Madison Valley History Association, believes this anchor ice is really what distinguishes the Madison River from others. "
But it is still a mystery to me. When I look at the gorged river, I don't think about all those different kinds of ice and slush, I just see the amazing beauty of nature and thank God I live in the middle of so much of it.
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