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• • Thorough analysis of WSRS-induced impacts on the river channel and delta. • • The natural hydrological cycle process has been altered by the artificial floods. • • Reservoirs regulation scheme altered the erosion–deposition regime of the riverbed. • • New light is shed on saving the global sinking deltas. The water and sediment regulation schemes (WSRS) orientated by dams have profoundly adjusted the hydrological process and geomorphological evolution of the lower Yellow River and delta. Two decades since the implementation of WSRS, the observed multidisciplinary datasets allowed us to systematically evaluate the impacts of this unprecedented engineering effort on the river-coastal system. The sediment fluxes transported to the sea showed a notable rebounded and coarsened process due to the erosion of the riverbed during the WSRS periods. The average median grain size of suspended sediment increased from 17.7 μm in the 1990 s to 26 μm in 2002–2009. The natural rhythm of hydrological process is fundamentally altered by WSRS, about 50% and 30% of annual sediments and water delivered to the sea for only 20 days. The water discharge system is more temporally dynamic and complex with higher dimensionality after the operation of WSRS. The erosion pattern has been a dominant feature in all the channel segments downstream the Xiaolangdi Reservoir, with an average total erosion volume of 1.02 × 108 m3/a after the WSRS. However, the erosion efficiency of the lower river showed a decreased trend, due to the riverbed had formed a coarse armored substrate for the continued scouring since 2002. The YRD has changed from the pattern of erosion to progradation for the increase of sediment supply, and the average growth rate of subaerial delta was about 6.89 km2/a during 2003–2014. The lessons learned from the operation of WSRS may provide a valuable reference for the management of global large river systems. [ABSTRACT FROM AUTHOR]

Abstract: In order to assess the extent of sediment connectivity between uplands and lowlands and to quantify the processes of in-channel deposition and remobilization, measurements of suspended sediment fluxes were conducted in a nested rural catchment of the Mexican Volcanic Belt. Data were collected over one year at three upland sites (3 to 12km2) and two downstream stations (390–630km2). Our results show that a structural discontinuity in the catchment (i.e. abrupt slope decrease at the junction between piedmonts and the alluvial plain from 2 to 10% to<0.1%) could be compensated by functional continuity during floods. Direct conveyance of fine sediment to the outlet occurred when a high stream transport capacity was reached. Erosion of the streambed was observed on various occasions and accounted for up to 50% of the flux leaving the catchment during one event. Conversely, temporary in-channel storage was apparent on other occasions, amounting to up to 52% of the flux recorded upstream during one storm. These two distinct behaviours were approximately equally distributed along the rainy season and strongly driven by the extent of coupling between surface and subsurface water. This work indeed highlights the role of baseflow spatial variations in determining the extent of lowland sediment conveyance. Riverbed erosional processes occurred when large differences in pre-event baseflow values (i.e. at least a twofold longitudinal increase) were observed between the 5-km distant lowland stations. Our findings outline the importance of systematically taking into consideration the baseflow parameter in research focusing on fine sediment transport across scales. [Copyright &y& Elsevier]