This dataset is composed of river monitoring, laboratory particulate Cs-137 measurements and rainfall monitoring used in the article: Vandromme, R., Hayashi, S.,Tsuji, H., Evrard, O., Grangeon, T., Landemaine, V., Laceby, J.P., Wakiyama, Y., Cerdan, O. The unprecedented soil decontamination program in Fukushima only reduced radioactive fluxes in rivers by 17% (PNAS, under review) River measurements were conducted by Hayashi S. and Tsuji H. A hydrological station was installed immediately upstream of Mano Dam Lake (Lake Hayama) in June 2014. The water height in the river was measured using an AquiStar PT12 pressure/temperature sensor (INW, Kirkland, WA, USA) at 5-min intervals and then converted into flow rate data using gage curves. Water and SS samples were also collected from the river section using an ISCO 6712 automatic water sampler (Teledyne Technologies, Lincoln, NE, USA) at 1-h intervals during flood events. The SS concentration was determined in the laboratory by filtration using a Whatman GF/F filter with 0.7-µm pores (Cytiva, Tokyo, Japan), and these concentrations were then used to convert the turbidity logs measured by a DTS-12 digital turbidity sensor (FTS Inc., Victoria, BC CANADA) at 5-min intervals into SS logs. This station was damaged by Typhoon Etau in September 2015. Following this damage, the data analysis and discovery of anomalies that persisted until the end of 2016 prompted us to omit the data acquired during this period. The hydrological station was subsequently moved a few hundred meters upstream in 2017. Water flows and sediment concentrations were subsequently acquired using the same systems described above at 10-min intervals until the end of 2019. River water samples were punctually collected to measure 137Cs concentration in Suspended Sediment (SS) (66 measurements during floods) from June 2014 to December 2019 (this chronicle ends in the middle of a flood). Station location before 2017 (coordinate system:WGS84) : lat 37.738391, long 140.803943 Station location after 2017 (coordinate system:WGS84) : lat 37.733191, long 140.807709 Rainfall record was acquired by the Fukushima Prefecture (Maenori station, lat 37.73644, long 140.74233, coordinate system:WGS84) at 10-minute time steps.