THE CORPS OF DISCOVERY IN THE COLUMBIA RIVER GORGE, OREGON AND WASHINGTON

As Lewis and Clark navigated the Columbia River through the Cascade Range, they observed a land of exceptional ecologic and geologic diversity occupied by a people sustained by the region’s natural resources. They were also traversing a landscape in the midst of dramatic change, with their visit marking a hinge point in the physical and cultural evolution of the river. The centuries before their visit were a period of tremendous earthquakes, landslides, and volcanic eruptions, all affecting the Columbia River and its tributaries. Many features produced by these events, such as the Bonneville landslide, were noted and interpreted by Lewis and Clark. Other observations refer more obliquely to important natural processes, such as large seasonal floods and persistent eolian transport. The major focus, however, of their observations in this reach were the numerous Native American settlements along the lower Columbia River, including trading and salmon fishing centers at “The Dalles of the Columbia” and Cascade Rapids. This rich culture and their supporting fisheries were in part developed and sustained by the cataclysms of the previous centuries. In the two centuries since Lewis and Clark, the hydrology, geomorphology, and settlement of the Columbia River Gorge has been radically transformed by changes of magnitude and consequence similar to those of the centuries before their visit. But instead of volcanism, floods, and landslides, the agents of change were cultural displacement, river regulation, and fisheries management. Diseases carried from Eurasia decimated the Native American population along the river corridor. Impoundment drowned Cascade Rapids and The Dalles of the Columbia, and in conjunction with past harvest and land management practices, substantially diminished wild fish populations. Dams and reservoirs on the Columbia River have reduced peak flows and sediment transport, as well as nearshore eolian sediment movement. While these changes have enabled many aspects of the present Pacific Northwest economy, they have fundamentally changed the nature of the Columbia River Gorge as observed by the Corps of Discovery.