River and Stream Alteration in the Western United States

In the western United States, widespread development has transformed much of the landscape, altering river systems and their ability to sustain services essential to the region’s ecology and economy. Because rivers continue to face a variety of stressors, there is an urgent need to quantify and document the status of rivers across the American West. The Disappearing Rivers project is the culmination of a comprehensive, science-driven effort by Conservation Science Partners—in collaboration with the Center for American Progress and Gage Cartographics—to elucidate how human development has altered rivers and streams in the eleven western states. As a continuation of the Disappearing West project, Disappearing Rivers seeks to enrich dialogue around opportunities for river conservation and restoration by providing a consistent and reliable accounting of the current status of stressors to flowing waters in the western United States.

Our overarching objective in modeling and mapping Disappearing Rivers was to quantify the degree to which rivers in the western US have been altered as a result of human activities. Specifically, we derived two fundamental metrics: flow alteration and floodplain alteration. These metrics were then combined into an estimate of the degree of total river and stream alteration. These data attributes are described in detail below.