What is Coeur d'Alene Lake's role in downstream flooding?
The Spokane County Flood Insurance Study says Coeur d'Alene Lake reduces peak flows on the lower Spokane River. The lake lowers the peak of the river downstream, although it does not remove the risk of high water in a wet year.
The lake sits upstream of the lower river, so its outflow is part of what determines how high the river gets below the city. A lake that holds back water in a wet year lowers the peak, but it does not stop the water from coming down from the surrounding land and the creeks.
For a homeowner, the practical point is that the lower river can flood in a wet year even with the lake's effect. The risk is lower than it would be without the lake, but it is not zero, and the Spokane County record shows high water in the river valley in several decades.
Why does the water stay in a lower level for so long on the river side?
Saturated ground along the river holds water against the foundation, and the drains and joints that would normally carry it away are slow when the river is high. Water can stay in a lower level for days after the river has dropped, which is why drying matters.
A river that is high for a long time keeps the surrounding soil wet. Water that enters the foundation has nowhere to drain, and the pump or the drain works against the river's level. The lower level stays wet until the river falls and the soil drains.
That is the reason a lower-river cleanup is planned around the readings rather than the first visit. The crew checks the moisture daily, and the drying continues until the framing and the subfloor reach target.
What affects the cost of lower-river water work?
The depth and duration of the water, the amount of silt, how many materials must come out, the number of drains and openings involved and the drying time all change the work. The price is explained and approved on site before any removal starts.
A short spike that left a few inches of water and a clean drain takes a short visit. A long high-water period that reached the framing, the stairs and the garage takes more equipment, more readings and more days of drying, and the crew sets the plan on the first survey.
Silt adds to the work. Deep silt from a long event has to be cleaned in layers, and the cleaning is part of the quote. The crew explains the layers and what each one involves.
Should I run a sump pump during a long river high-water period?
Yes, when the water is rising in the lower level, and keep the discharge line clear of the house. A sump that cannot keep pace should be recorded and checked by a plumber. Do not rely on a pump alone during a long high-water period.
A sump pump is designed to remove water from the basin, but a river that stays high can push water in faster than the pump can clear it. Test the pump before the event, and check the basin and the discharge line during it.
If the pump fails, or the water keeps rising while it runs, call a plumber and then a crew. Do not stand in water to reach the pump, and do not run its cord through standing water.
What should I keep for my insurer after a river high-water event?
Keep the crew's record of the water line and the duration, the photographs, the removal list and the drying readings. Ask your insurer directly how a river event is treated under your policy, because outside water and flooding are often handled differently from water inside the home.
The highest water line on the walls is the single most useful record, because it shows how high the water reached. Photograph it with a reference such as a measuring tape, and keep the photograph with the crew's record.
The Washington Office of the Insurance Commissioner handles consumer complaints about how claims are handled. The insurer and your policy decide what applies to a particular event.