The dataset contains denitrification, anaerobic ammonium oxidation (anammox) and nitrification activity of riverine sediments in the Hampshire Avon catchment (UK). Six rivers within sub-catchments of contrasting geology (clay, sand, chalk) were investigated. Data were obtained via direct, field-based measurements in seasonal campaigns conducted between spring 2013 and winter 2014. Also included are chemical parameters determined in porewaters prior to in situ rate measurements.