This dataset contains anaerobic ammonium oxidation (anammox) and denitrification activity of riverine sediments in the Hampshire Avon catchment (UK). Nine rivers within sub-catchments of contrasting geology (clay, sand, chalk) were investigated. Data were obtained via laboratory incubations (potential data) and direct, field-based measurements (in situ data) in summer 2013. Also included are chemical parameters determined in porewaters prior to in situ rate measurements.