In the fall of 2014 (October-November) the U.S. Geological Survey in cooperation with the U.S. Army Corps of Engineers collected sediment samples (suspended and bed material) at several sites on the Niobrara River in Nebraska near the Spencer Dam prior to, during, and immediately after a sediment-flushing event. Suspended-sediment samples were analyzed for sediment concentration and percent finer than sand. Bed sediment samples were analyzed for particle-size distribution using standard classes by sieve analysis. In addition, a Sequoia LISST Streamside particle-size analyzer (PSA) was deployed during the first week of the flush; this unit collected suspended-sediment concentration and grain-size data. Sampled sites included the bridge on U.S. Hwy 281, county road 508 Ave bridge south of Lynch, Nebr., and the county road bridge south of Verdel, Nebr. This part of the data release consists of discrete suspended-sediment and bed-sediment data tables, PSA data tables, and a data table of results from discrete samples collected manually at the intake to the PSA. An accompanying shapefile of sample locations may be found at https://www.sciencebase.gov/catalog/item/5a5e1596e4b06e28e9be47db.