After the construction of the Three Gorges Dam (TGD) in China, the downstream has been affected by the reduction in sediment discharge and regulation of flow processes, which have resulted in severe scouring and changes hydrological regime. Consequently, the spawning ground of Chinese sturgeon distributed along the downstream Yichang reach could be affected. This study examined the effects of TGD on the streamflow, sediment load and channel morphology downstream based on in situ measured data. Results showed that, after the impoundment of the TGD, sediment load at the downstream Yichang hydrological station decreased significantly, and the Yichang reach continued to be scoured. The distribution of erosion was uneven, and the scouring mainly occurred in the branching channels. The channel gradient and riverbed roughness increased with the erosion of the river cross section. After more than 10 years of erosion, the riverbed scouring and armouring in the Yichang reach was basically completed, thus we expected that the spawning grounds of Chinese sturgeon could be retain as the riverbed tends to be stable. The findings in this work have implications in the protection of the critically endangered Chinese sturgeon.

Spatiotemporal variations of sediments transported along rivers play a crucial role in a wide spectrum of uses, such as navigation, recreation, habitats or river environmental protection. The advancement in technology has made it possible to use various indirect techniques to study and evaluate the transport of suspended sediment in fluvial environments. To investigate large-scale phenomena, remote sensing is becoming a largely utilized approach, as it allows to combine spatially distributed and local information. The systematic change of suspended sediment concentration (SSC) and dynamic processes controlling sediment transport at a given local scale are often not well known, and generally investigated using reach-specific field information. In this work, SSC maps were created by combining satellite images with local monitoring in situ SSC data, using the Zhijiang-Chenglingji reach of the Changjiang River (China) as a case study, and analyzing how SSC dynamics changed over the period 2016–2023, considering both low- and high-flow events. Multiple relationships between measured SSC and reflectance were selected from the literature and tested. Results show that a combination of Sentinel-2 bands 3,4, and 5 represents the best-performing statistical model (R ² = 0.73) in mapping SSC spatiotemporal variations over an extent of dozens of kilometers. Despite the uncertainties connected to the small amount of data available and the differences between SSC data measured over the vertical and surface reflectance, this application shows the potential of remote sensing in mapping SSC at a large spatial scale, overcoming the limitations of localized field sampling, eventually suggesting a relatively simple approach that could assist water managers in mapping large-scale dynamics of SSC for applications such as navigation, habitat preservation, and hydropower production.