The Upper Clark Fork River (UCFR) has a long history of contamination, including a flood in 1908 where heavy metal mine tailings were distributed across the channel and floodplain. Our study investigated how restoration due to legacy contamination influences the DOM quality and quantity over a five-year period to better understand patterns of aquatic health following restoration using a carbon cycling perspective. The study will showcase how aquatic ecosystems are influenced by the re-establishment of a ‘flood pulse’ by restoring the river’s connection to its floodplain and what carbon quality signals may serve as healthy ecosystem markers after metal contamination restoration. Our results showed DOC concentrations exhibited distinct annual cycles, with increases during high discharge events. Average DOC concentrations were largest in spring and gradually declined to winter. Excitation Emission Matrix-Parallel Factor (PARAFAC) analysis modeled five fluorescence components, describing humic- and protein-like DOM of varying sizes, reactivities, and origin. More labile, autochthonous microbial-like DOM had more spatial and temporal variation, as expected during the spring summer seasons. From 2017-2022, DOM character increased abruptly in aromatic and more plant/soil “humic-like” nature, determined from specific ultraviolet absorbance at 254 nm (SUVA254) and PARAFAC analysis reflecting more terrestrial contributions to the river. Fluorescent humic-like terrestrial signals were dominant from upstream to downstream sites seasonally and annually. Fluorescent DOM temporal variability dominated over spatial variability. Humic-like fluorescence showed synchronous trends during high hydrological connectivity. Interestingly, during the Fall 2018, despite lower DOC concentration, the dominant chemical character was large humic-like DOM. Protein-like fluorescence increased during baseflow as expected, reflecting in-stream production and processing. Fluorescence index (FI) decreased longitudinally and humification index (HIX) increased temporally and spatially, indicating that DOM character was more terrestrial and humified as water moves downstream over time. Furthermore, tributaries exerted a strong control on DOM composition throughout the river by acting as a source and/or diluter.