Today's deltas are impacted negatively by (1) accelerated subsidence (e.g., from ground fluid extraction), (2) global eustatic sea level rise, and (3) decreased sediment supply, which increasingly starves these landforms of sediment necessary to sustain their footprint. This growing vulnerability threatens many megacities that have developed due to the rich resources offered by deltas and therefore urgently calls for efforts to maintain sustainability. The Yellow River of China is classic example of such a landform under threat and which requires human intervention to maintain its resilience. Since 2002, the Yellow River Conservancy Commission has enacted an annual water and sediment regulation scheme (WSRS) by coordinated operation of three large reservoirs in the mainstream. Here we evaluate the efficiency and sustainability of this man‐made experiment on delta evolution. The impulsive delivery of muds and sands, within ~20 day intervals (averaged duration of the WSRS), did indeed move the present Yellow River delta from a destructive phase to an accretion phase. With continuous scouring, however, the downstream riverbed erosion efficiency has decreased, due to coarsening of surface bed material sediment. Concomitantly, sediment delivery has decreased, resulting in the present delta once again entering an erosive (destructive) phase, since 2014. From a perspective of delta restoration, the WSRS on the Yellow River is effective but potentially unsustainable. Restoring delta resilience necessitates an enhanced, coordinated effort, relying upon new sciences advances, rather than simply assuming channel scour will address the sediment deficit of the delta.

The Yellow River is one of the most significant sources of terrestrial sediment to the global seas, and the Bohai Strait is the only pathway that delivers Yellow River‐derived sediments from the shallow Bohai Sea to the Yellow Sea. To investigate sediment transport processes through the strait under the influence of storms (strong northerly winds) that frequently occur in winter, we deployed two sets of observing platforms equipped with Acoustic Doppler Current Profilers (ADCP) and a suite of other sensors in the strait in January 2018. Aided by a system of high‐resolution models, we reconstructed sediment dynamics in response to the strong northerly wind of a winter storm. Model results show that the instantaneous suspended sediment flux (SSF) is highly aligned with tidal currents, while the net sediment flux has a clear dependence on variations in exchange flow and sediment resuspension. Enhanced coastal currents, intensified wave motions, and higher suspended sediment concentrations indicate that the through‐strait sediment flux during outflows is greater than during inflow conditions. Such SSF asymmetries are believed responsible for the net sediment export through the Bohai Strait in wintertime. Diagnostic analyses provided insights into the dynamic mechanisms of exchange flow variations influenced by both the strong northerly winds and the wind‐triggered coastal trapped waves in the shallow, narrow strait via geostrophic effects. This study highlights the importance of storm‐induced horizontal exchange processes in a coupled bay‐shelf system.

Sediment gravity flows are the most direct and efficient transport mechanisms for moving terrestrial sediments into deep oceans. Scarcity of firsthand measurements, however, has hindered the quantitative, even qualitative characterization of such flows. Here we present a unique year-long data record from ~4000 m depth in the Manila Trench that captured two very different gravity flows in terms of their hydraulic and sedimentary properties. The first flow was of slow speed (~40 cm s⁻¹) and long duration (~150 h), thus nicknamed ‘Tortoises’, and carried very fine sediment with low concentration (~0.01%). The fast (~150 cm s⁻¹) but short-lived (~40 h) flow, nicknamed ‘Hares’, carried much coarser sediment with higher concentration (~1.2%). Clay mineral compositions suggest that the ‘Tortoises’ originated from upstream canyon wall slumping, whereas the ‘Hares’ was likely submarine canyons southwest of Taiwan Island due to typhoon. Grain size is a key factor in determining evolution of turbidity currents.

Straits are both a choke point and passage through which material and energy are exchanged between two adjoining water bodies. Understanding the mechanisms that drive these exchanges therefore is vital to quantifying the water and sediment budgets in regional and global oceans. Here we present a study in which a novel, phase‐averaging method was employed to better estimate the net‐suspended sediment fluxes through the entire Bohai Strait, the only passage for the massive Yellow River‐delivered sediment to leave the enclosed Bohai Sea for the open Yellow Sea. In winter, the transport through the strait was nearly barotropic in waters well mixed by the energetic winter monsoons. The transport became primarily baroclinic (opposite directions between upper and lower layers) in spring due to stratification, especially in the southern part of the strait. Intermittent but frequent southerly winds in northerly dominated winters were responsible for a net westward sediment transport into the Bohai Sea, a finding contrary to a status quo view. Hence, previous studies in which these intermittent southerly wind busts were not included are believed to have overestimated the sediments export from the Bohai Sea.