Geomorphic mapping establishes the basic context for understanding modern channel conditions by (1) defining major elements of the late Cenozoic geologic history shaping the geomorphology of the study area; and (2) outlining the active geomorphic floodplain, which is the domain for assessing channel change and floodplain vegetation conditions. The mapping domain broadly corresponds with the extent of Light Detection and Ranging (LiDAR) topography acquired in November, 2004 (Watershed Sciences, 2005) and includes the broad alluvial valleys of the lower Sycan River, mainstem Sprague River, and lower North Fork of the Sprague River. The mapping encompasses the main floodplains and contiguous alluvial and colluvial landforms. The geomorphic mapping was based on aerial photographs, LiDAR topography acquired in November 2004 (Watershed Sciences, 2005), U.S. Geological Survey 7.5-minute topographic maps, existing soil mapping (Cahoon, 1985), prior geologic mapping (primarily Sherrod and Pickthorn, 1992), reconnaissance field observations, and stratigraphic sections, primarily along bank exposures but supplemented by augering.