Before the Ice Age floods, no stream or waterfall existed here. Instead, the Palouse River flowed through Washtucna Coulee. What caused the river to jump its course?
When the floods surged across the area, they cut a path through the fractured basalt beneath the Palouse Hills. Today, the river continues to follow the route created by the floods.
Transforming a Landscape
The floods stripped away hundreds of feet of soil and carved a maze of coulees, abandoned river channels, and buttes that extend 11 miles between Washtucna Coulee and the Snake River.
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Now dry, Washtucna Coulee was once the channel of the Palouse River.
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The floods overwhelmed existing rivers and streams, spilling over the landscape and slamming into the Snake River. Most of the water flowed downriver towards the Columbia River, but some was forced upriver to Lewiston, Idaho and beyond.