Deschutes National Forest

Geology
Gorp.com

Originating at Little Lava Lake, the river flows 87.4 miles through the Deschutes National Forest to the City of Bend. It joins the Columbia River upstream from The Dalles, Oregon. The river stretches for a total length of 252.2 miles. Most of the upper flow of the Deschutes River is through public land, although portions flow past private holdings.

From Wickiup Reservoir to Benham Falls, the Deschutes River flows through sediments left by ancient lakes and streams. The river has been dammed many times by lava flows and lava domes in the Benham Falls/Lava Butte area. The river now cuts through a lava dome at Benham Falls.

The excellent rafting on the upper Deschutes River below Benham Falls is attributed to a lava flow 6.200 years ago. The lava poured out of Lava Butte (the site of the Lava Lands Visitors Center), spilling into the Deschutes River in five places (see map). The flow dammed and narrowed the river channel, creating thunderous. cascading rapids at each point. Behind each lava dam, the water backed up into smoother sections of river. At Dillon Falls the river cascades over an old fault scarp. Lava dams from Lava Butte create alternating sections of smooth water and whitewater rapids.

Erosion in past centuries has reduced the violence of the rapids so that three of the five lava outcrops are now safe for rafting. Whitewater raft trips usually begin above the fourth lava flow dam and end above the fifth dam (Lava Island Falls).


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