Floodplain structural and compositional vegetation data were collected to determine the structural biodiversity of floodplains along the Sacramento River. Thirteen floodplain transects were collected from August to September 2008 along the Sacramento River between Red Bluff and Colusa. Each transect traversed multiple land-age classes, substrates, and vegetation types. We collected structural data including tree occurrence information as well as species compositional data via intensive modified-Whittaker plots. A GPS point was taken at each tree larger than 10 cm dbh within 2 meters from the transect line. Tree species, tree height, diameter at breast height (DBH), and crown radius of each tree were entered into TerraSync using Trimble ProXT. Species composition was analyzed through intensive modified Whittaker plots located in each unique vegetation type or floodplain age along the transect line.