High Water, High Winds Destructive Combination Threatens To Erode Shorelines, Damage Docks
Batten down the boat docks.
The lake is rising and the winds are picking up.
The lake is expected to reach an elevation of 2,130 feet - 2 feet over summer level - by the weekend. Wind gusts are expected to reach 35 miles per hour at times.
The National Weather Service issued an advisory Thursday that high water and winds could cause some lowland flooding and some bank erosion along the northern and eastern shores of Lake Coeur d’Alene.
The combination also could cause some damage to docks.
“It really does a number on them,” said dock-builder Tom Frey. “People need to get to their lake places and make sure everything’s all right and in one piece.”
Frey advised dock owners to make sure their dock is secured to shore.
“The best thing to do is get a line, some three-quarter or five-eighths inch nylon line, and tie it to a tree,” he said.
After all, if the dock floats away, it might end up battered and broken on the beach at North Idaho College, and it could cost $5,000 to $12,000 to replace.
“We get a lot of stuff washed up on shore,” said NIC grounds maintenance director Mike Halpern. “Anything from logs to old docks that got cut loose on the lake, old inner tubes, you name it.”
The debris gravitates to the NIC beach because that’s where the lake empties itself into the Spokane River.
The problem is, there’s more water surging into Lake Coeur d’Alene than can leave, which means the lake level keeps rising.
On Thursday, the St. Joe and Coeur d’Alene rivers were moving 25,000 cubic feet of water per second. The Spokane River was leaving the lake at a rate of 21,000 cfs.
As the lake rises, it backs up into the St. Joe and Coeur d’Alene rivers, exacerbating flooding problems there. So far, neither river has reached flood stage.
Washington Water Power has the spill gates at its Post Falls dam wide open. But even if the dam wasn’t there, Lake Coeur d’Alene and its tributaries would still flood, WWP hydrologist Don Felgenhauer said.
The point where the Spokane River leaves the lake forms a natural bottleneck. At summer level, the river is only 10 feet deep there, and the river moves about 15,000 cfs.
“The only mechanical means we have to get the water out of the lake is to increase the height of the lake,” Felgenhauer said. “It’s a self-regulating, natural type thing that happens.”
WWP reminded residents that significant safety hazards exist above and below the dam, particularly during this time of high water.
Lake Coeur d’Alene isn’t the only lake still rising because of the runoff from a record mountain snowpack.
Hayden Lake rose about a half-inch between Wednesday and Thursday, and the water coursing over a temporary spillway continued to eat away at the lake’s levee.
The spillway, a 4-foot depression in the dike, is lined with sandbags and a giant plastic sheet. Somehow the plastic tore on the backside of the spillway, and the water is eroding it.
The county has been positioning sandbags on the backside of the spillway for two days. On Thursday, firefighters dressed in dry suits were carefully placing sandbags in strategic spots on the spillway.
Despite the large volume of water leaving the lake, there is little threat of flooding downstream, said Sandy Von Behren of Kootenai County Disaster Services. The water enters a field of porous gravel and percolates down to the aquifer.
If Kootenai County residents do fear flooding on their property, they can pick up sandbags at any fire station, and fill them at area concrete or gravel businesses.
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