[en] One mechanism affecting the dispersal of radioactive materials in water bodies is radionuclide adsorption by sediment. Consequently, sediment transport is a major factor to consider when evaluating radionuclide migration. As a part of a study on sediment and radionuclide transport in rivers, Pacific Northwest Laboratory (PNL) is investigating the effect of sediment on the transport of radionuclides in Cattaraugus and Buttermilk Creeks, New York, during different flow conditions. Sources of radioactivity in these creeks were a low-level waste disposal site and a nuclear fuel reprocessing plant. Reprocessing operations were terminated in 1972 and waste disposal was discontinued in 1975. Other sources of radioactivity include fallout from worldwide weapons testing and natural background radioactivity. The major objective of the PNL Field Sampling Program is to provide data on sediment and radionuclide characteristics in Cattaraugus and Buttermilk Creeks to verify the use of the Sediment and Radionuclide Transport model, SERATRA, for nontidal rivers. The program is divided into three phases: Phase 1, medium-flow condition; Phase 2, low-flow condition; and Phase 3, high-flow condition. To date, results have been obtained primarily for the Phase 1 portion. For the Phase 1 sampling, 10 transects were established to collect data on flow and channel, water, sediment, and radionuclide characteristics. Some radiological analyses were made on samples of water, suspended sediment, and bed sediment