The United States Geological Survey (USGS) Center for Coastal and Watershed Studies, the National Aeronautics and Space Administration (NASA), United States Bureau of Reclamation (Reclamation), Idaho Department of Water Resources (IDWR) and a consortium of local city, county agencies and private entities (see supplemental information) are using airborne LiDAR to measure the submerged topography of the Boise River. The study area encompasses the 500 year floodplain from Lucky Peak Reservoir to the confluence of the Boise River and the Snake River. Elevation measurements were collected in March of 2006 using the NASA Experimental Advanced Airborne Research LiDAR (EAARL). Initially developed by NASA and Wallops Flight Facility (WFF) in Virginia and now administered by the USGS Coastal and Marine Geology Program, EAARL measures ground elevation with a vertical accuracy of roughly 15 centimeters. The data were processed by IDWR using the Airborne LiDAR Processing System (ALPS), a multi-tiered processing system developed by a USGS/NASA collaborative project for the use of subaerial and submarine LiDAR. The output from this processing is 2 meter resolution raster data that can be easily ingested into a Geographic Information System (GIS). The data were organized as 2 km by 2 km data tiles in ERDAS imagine format. Point data information is also available for first return, bare earth, submerged topography and a submerged topography/bare earth combination. These tiles are created for visual interpretation and regional quantitative analysis. The data are in UTM Zone 11 meters, NAD83, NAVD88 (Geoid 03 model). At the same time that the Boise River LiDAR data were collected, USGS collected cross sectional data using survey grade GPS at three separate sections along the river – upper, middle and lower. These ground observations were then used to quality check the LiDAR data and to provide a vertical accuracy assessment. The results of the quality assessment will be available by the end of December, 2009.