All year, Peg and I live on the River at Devil's Elbow (I tend to think of the Au Sable as the River with a capital R). I enjoy observing the world of the River and it's adjacent environment on a day to day basis. Hopefully it will be of interest to those who enjoy and love the Au Sable, but can't observe the valley throughout the year, to read about some of the "River events."
Our home is five bends downstream from McMaster's Bridge. The bends that we live on are very sharp and in logging days of the past the log drives would jam on these sharp bends, hence the loggers named them "The Devil's Elbow." We preserved the name for our house. This is big water and what I observe may not be common to the smaller upstream reaches. Here, the River freezes under certain conditions. In the winter of 1995-96, it was frozen three different times for a total of 29 days. In the winter of 1997-98 it never froze. This year it was frozen for two weeks in January and with spring coming it should not freeze again.
For the River to freeze there must be certain circumstances. As Bob Linsenman stated in his new book "River Journal—Au Sable," the Au Sable is a spring creek. This means that water of approximately 55°F is constantly seeping into the flow at every bend. These springs keep the River cool in the summer and warm in the winter. The Au Sable, at Devil's Elbow, freezes when the air temperature gets cold enough to counteract the springs and lower the water temperature sufficiently to form anchor ice, also called "frizzle" ice.
When the night air temperature drops to 0F or lower, anchor ice forms on the bottom in the shallow, more turbulent portions of the River. Water becomes lighter as it approaches 32F. This, of course, is why lakes freeze from the top down. In a river where anchor ice forms on the bottom, water molecules still follow the laws of nature and become lighter as their temperature drops toward 32 degrees. These lighter molecules on the verge of freezing get tumbled in the turbulence of the more shallow riffles. One of these molecules hits a rock and adheres to it. Another molecule hits and adheres to the first. More and more molecules, just at freezing, adhere to each other and soon there is a mass of anchor ice on the bottom of the riffle. Eventually the mass of soft, slushy ice breaks loose and rises to the surface to float downstream as slush ice. I remember as a boy wading through the soft, but slippery anchor ice on the bottom when I ran a trapline on a mountain stream in north-western Pennsylvania.
I have seen pieces of anchor ice as big as a dining room table pop to the surface. When the morning sun hits the River's surface, more ice seems to break loose from the bottom in a short period of time.
In order for the River to freeze there must be two or three consecutive nights when the air temperature drops to 0F. or colder, and does not rise above 10 to 15F during the day. When this occurs the River's surface will be almost completely covered with the floating slush ice throughout the day. This ice will often form a dam at a narrow place in the River or where the River slows down. This usually occurs down-stream from our house near Mac's Island.
In front of Devil's Elbow, you can see the River begin to slow and then to rise. It will rise two to three feet or more and cover the low areas on the inside of the bends within several hours. Soon you can see the ice backing up as more and more of it floats into the upstream edge of the ice covering the River. As the ice backs up, the sound of the river becomes muted, but you can hear the soft hiss of ice brushing ice.
Once frozen the River will remain covered with ice as long as the cold weather holds. The slushy ice that formed the original covering will freeze into solid ice and become thicker and thicker. I have often seen deer, turkeys, coyotes, and other game cross the ice after the River had been frozen for several days, and once I ventured out to the middle of the River so that Peg could get a photo of me on the ice.
When the weather moderates, warmer spring seepage will begin to prevail. When the night air temperature rises to 20F or higher, the ice will go out in a few days. As the ice breaks up it creates an awesome sight and sound. Channels will form, close up, and then reform. Large slabs will float down and slide under other slabs forcing them into a vertical position with three to five feet of ice projecting into the air. These come crashing down as the current shifts the ice. Within several hours, the main channel will have cleared and the river level drops several feet. We always hope the "ice out" occurs in daylight when we are home.
How does this cycle of anchor ice-to-frozen-river to ice-out affect the trout and their food chain? All the biologists with whom I have talked agree that the river bottom and it's inhabitants can be seriously impacted. There is a potential for damage both when the anchor ice forms and rises to the surface and when the ice goes out. In his two-volume work Trout, Ernest Schwiebert states, "Finally, the buoyancy of the ice is sufficient to uproot it from the bottom, ripping free food-sheltering layers that become imbedded in the cakes.
Sometimes there is sufficient current to sweep the ice down-stream, terribly grinding and damaging the river bed. Such ice floes cause great damage to both the spawning redds, and anchor ice can often explain some relatively barren streams." The cycle does provide good to some however. Every time the ice freezes, and again when it goes out, there is a large increase in sightings of eagles hunting the river. This year two eagles vied with several ravens for a deer carcass that the ice had deposited on the log jam below the house. The eagles won. RWOL
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