Many tidally-dominated estuaries of the world are experiencing variations in bottom topography due to changes in natural forcings and intensive human activities. Here we focus on the morphological evolution of the North Branch (NB), a tidallydominated distributary of the Changjiang estuary. Our analysis is based on long-term bathymetric and hydrological data collected between 1950 and 2010. The results show that mean water depth, channel volume below 0 m, and channel volume below-5 m have respectively decreased by 43%, 53% and 92% in the last 50 years. A reduction of the whole estuarine surface with aggradation in elongated tidal sand bars and erosion at the mouth are the main morphological variations of the NB, while a decrease in channel volume below-5 m due to infilling is the second mode of morphological change. While the drastic decrease in sediment load from upstream is likely unrelated to the silting of the NB, local land reclamation along the banks is directly responsible for the reduction of estuarine surface area and related tidal prism. Between 1958 and 2013, enhanced flood-tide currents resulted in a large import of sediments from offshore into the NB, triggering a sustained decrease in channel volume below 0 m. It is argued that the recovery of the funnel-shaped configuration of the estuary by restoring mud flats over 0 m, dredging the southern part of the estuary bend and forbidding land reclamation could prevent the silting of the NB, otherwise the NB will likely vanish in few decades.

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The current study investigates how long-term Tai Chi experience affects the neural and emotional response to regret in elders. Participants perform the sequential risk-taking task while undergoing functional magnetic resonance imaging (fMRI) scanning. In the task, participants opened a series of boxes consecutively and decided when to stop. Each box contained a reward, except for one which contained a devil. If the devil was revealed, then this served to zero the participant’s gain in that trial. Once stopped, participant’s gains and missed chances were revealed. Behaviorally, the Tai Chi group showed less regret, reduced risk taking, higher levels of nonjudgment of inner experience and less emotional sensitivity to outcome. fMRI results showed that the Tai Chi group demonstrated stronger fronto-striatal functional connectivity in trials with numerous missed chances. The nonjudgment of inner experience mediated the impact of fronto-striatal functional connectivity on Tai Chi practitioners’ emotional sensitivity to outcome. These results highlight that long-term Tai Chi exercise may be effective in alleviating feelings of regret in elders by promoting reduced judgment of inner experience and enhanced emotion regulation through the strengthening of fronto-striatal functional connectivity.

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Net sediment transport is predominantly seaward in fluvial-dominated estuaries worldwide. However, a distributary branch in the Changjiang Estuary, the North Branch, undergoes net landward sediment transport, which leads to severe channel aggradation. Its controlling mechanism and the role of human activities remain insufficiently understood, although such knowledge is necessary for better management and restoration opportunities. In this study we revisit the centennial hydromorphodynamic evolution of the North Branch based on historical maps, field data, and satellite images and provide a synthesis of the regime change from ebb to flood dominance. The North Branch was once a major river and ebb-dominant distributary channel. Within which alternative meandering channels and sand bars developed. Deposition of river-borne sediment leads to infilling of the branch, while tidal flat embankment reduces the bankfull width and modifies the channel configuration, resulting in a profound decline in the sub-tidal flow partition rate. The North Branch then becomes tide-dominant with an occurrence of tidal bores and elongated sand ridges. Once tidal dominance is established, extensive tidal flat reclamation enhances the funnel-shaped planform, amplifying the incoming tides and initiating a positive feedback process that links tidal flat loss, sediment import, and channel aggradation. Overall, the shift in branch dominance is a combined result of a natural southeastward realignment of the deltaic distributary channels and extensive reclamation. One management option to mitigate channel aggradation is to stop the aggressive reclamation and allow tidal flats to build up, which might reduce the sediment import and eventually lead to a morphodynamic equilibrium in the longer term. Understanding the impact of tidal flat reclamation is informative for the management of similar tidal systems under strong human interference.

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