The project will not change the lake’s authorized runout elevation, which is the legally set height for stop logs that control water levels. Stop logs are removable barriers used to raise or lower the dam’s water-holding height. The authorized elevation, set by DNR Waters, aims to retain as much water as possible while avoiding flood damage complaints.
Currently, the lake’s runout is about 0.6 feet higher than authorized due to an illegal dam modification made between 2011 and 2012. To maintain current water levels, the new design will include a narrow notch at the authorized elevation, while the rest of the rock arch rapids will be higher. As a result, lake levels will stay within a few hundredths of a foot of current levels under normal flow conditions.
Extensive modeling confirms the design will closely match recent lake levels and meet FEMA requirements for no increase in flood elevation during a 100-year flood. Under normal and high flows, water levels will remain nearly the same. During very low flow, levels will drop slightly but still stay higher than if the entire structure were set at the authorized elevation.
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