The Yellow River is difficult to control. Little water and a large amount of sediment results in sediment accumulation in its lower reaches as sediment inflow exceeds transport capacity. Reducing this sediment deposition is essential for harnessing the Yellow River. Included in this process is the rational use of the sediment. Many researchers have investigated usage of Yellow River sediment as an aggregate material for concrete production, but there are still some problems (e.g., low resource utilization and low strength of the concrete made from Yellow River sediment). To make up the deficiency in the existing research, this study proposes two methods of sediment utilization. One is to use Yellow River sediment to build embankments, and the other is to use ultra-fine Yellow River sand to prepare ultra-high-performance concrete (UHPC). Test results reveal that the prepared high-strength concrete performs well in each test, including: fluidity, mechanical properties, pore structure, ecological evaluation, microscopic measurement of the interface transition zone, and economic analysis.

The sedimentation basin is an important part of hydraulic engineering. Because the prototype size is too large and not easy to analyze, Mike 21 has the advantages of easy input, conversion, analysis, and demonstration of data results, which are flexible and convenient; however, this method has not been used in hydraulic engineering by previous researchers. This research used the sedimentation basin of the Yellow River Diversion Project as the research object, and a simulation model of the sedimentation basin channel #1 was developed using Mike 21 software to analyze its water and sediment characteristics and conditions in different periods. Using numerical simulation methods, three types of sedimentation basin operation schemes were targeted, the sedimentation changes and sedimentation law of channel #1 were evaluated in each scheme, and the sedimentation effects were compared. The results show that in conditions of different incoming water and sediment and diversion timings during the flood and non-flood seasons, the sedimentation basin adopts an operation scheme to lower the outlet water level, and the siltation volumes are 180,000 and 150,000 m³ lower than the high-outlet water levels, respectively. Moreover, its siltation status is significantly improved, which can effectively extend the service life of the sedimentation basin, prolong the period of silting removal by about 3.5 months, and provide a scientific basis and reference for the optimization of the operation mode of the sedimentation basin in other types of hydraulic engineering.

Coreius guichenoti, once widely distributed in the upper reaches of the Jinsha River, has become a nationally protected species in China due to the profound impacts of cascade reservoirs. To assess the influence of substrate on the suitability of spawning habitat for C. guichenoti, this study develops a substrate-inclusive habitat model using fuzzy logic based on expert knowledge. Taking the Pingdi Town section of the lower Jinsha River—a historical spawning site for C. guichenoti—as a case study from March to July 2020, we simulated changes in the spawning habitat suitability index (HSI) and compared the results with those from traditional models that exclude substrate factors. The results showed that in the first and second halves of May, Weighted Usable Area (WUA) and Overall Suitability Index (OSI) increased by 42.31% and 38.73%, respectively, while MSP exhibited dramatic increases of 236.04% and 614.56%. These improvements were primarily observed along the riverbanks, where HSI increased by approximately 0.25. From a management perspective, the HSI results provide a scientific basis for optimizing ecological flow regulation. Incorporating substrate factors into spawning habitat models offers a more objective and comprehensive assessment of habitat quality. Habitat restoration measures, such as targeted substrate improvement in key riverbank areas, may further increase habitat suitability, providing additional opportunities for conservation planning in regulated rivers.

The floodplain transverse slope is a significant parameter reflecting the degree of development of a secondary suspended river, as well as a crucial index of the flood risk in the river channel. Clarifying the factors that influence the evolution of the floodplain transverse slope has always been a hot and difficult topic for researchers working on the Yellow River management. We took the severe section of the secondary suspended river from Dongbatou to Gaocun in the lower Yellow River as the research object, selecting the annual runoff, annual sediment load, annual sediment coefficient, and the intensity of flood-season flow scouring at the Huayuankou station in the downstream as the water–sediment indexes. The correlation between different water–sediment indexes and the floodplain transverse slope under three modes: interannual, flood season, and flood-season overbank was studied through methods such as cross-wavelet transform and wavelet coherence analysis. The results showed that under the three modes, the annual sediment load and annual sediment coefficient had a high correlation with the evolution cycle of the transverse slope, followed by the intensity of flood-season flow scouring, and the annual runoff had the lowest correlation. Meanwhile, the change in the transverse slope had a good correlation with the flood-season overbank mode, indicating there was a high similarity between the water–sediment characteristics of floodplain flooding and the evolution cycle of the transverse slope; that is, the change in the transverse slope is greatly influenced by floodplain flooding events.

The annular flume is an ideal hydrodynamic test device for studying river sediment, and it has been widely used in recent years to study the movement patterns of sediment and other particulate matter. Annular flumes have made outstanding contributions to research in fields related to sediment transport and the diffusion and migration of pollutants. The existence of circumfluence structures in annular flumes leads to complex and variable flow structures. To obtain a more stable and controllable water flow structure, a sophisticated three-dimensional mathematical model based on the Fluent software was established to study the development law of water flow structure in the flume by changing the size of the annular flume speed ratio. The results show the following: (1) The overall trend of the simulation results basically matched with the measured results; the average relative error was 3.54% and the Nash efficiency coefficient was 0.9934, close to 1. The model calculation data were highly credible. (2) The axial flow velocity of the water tank gradually showed a “U”-shape distribution with the increase in the speed ratio. (3) When the speed ratio was R ≤ 0.17 (where the speed ratio R refers to the ratio of annular groove to shear ring speed), there was only one vortex in the tank; when the speed ratio was R > 0.17, there were multiple vortices in the tank, and the flow pattern was more complicated. (4) When the rotational speed ratio R = 0.28, the secondary flow intensity of the annular flume reached the lowest point, which was only 39.28% of the secondary flow intensity of the conventional annular flume. (5) It was determined that the annular flume water flow structure was most stable and controllable when the rotational speed ratio R = 0.24. The results of the study can provide a further theoretical basis for research on sediment dynamics and its related fields conducted by applying an annular flume.

Secondary perched rivers are extensively distributed in the lower section of the Yellow River, and their condition is grave, representing a significant peril to the flood control safety of this region. Consequently, conducting an analysis of their evolution characteristics holds immense engineering importance for ensuring the flood control safety of the lower reaches of the Yellow River. This study focuses on the downstream section of the Yellow River, specifically from Dongbatou-Taochengpu. This research is based on extensive data, including topographic measurements of large cross-sections and water and sand data from Huayuankou spanning from 1960 to 2022. The transverse slope of the beach, which indicates the level of development of the secondary perched rivers, was chosen as the calculation index. To analyze the trend and mutation of the transverse slope, statistical methods such as the Theil–Sen slope estimation, Mann–Kendall test, Pettitt test, and double cumulative curve method were employed. The findings indicate that the average transverse slope along the wandering section (Dongbatou-Gaocun) is 5.81‱, is significantly lower compared to the transitional section (Gaocun-Taochengpu), with an average transverse slope of 8.89‱. Furthermore, the range of fluctuation in the variation in the transverse slope along the wandering section (3.19–8.18‱) is considerably narrower than that observed in the transitional section (2.94–19.51‱). Prior to the implementation of Xiaolangdi, there was a significant increase in the transverse slope. Notably, the transitional section experienced a sudden change in 1975, while the wandering section experienced a sudden change in 1990. The abrupt alteration in the transitional section can be attributed to the substantial variation in the water and sand conditions. Conversely, the sudden change in the wandering section resulted from the insufficient flow rate of the flat beach. However, following the implementation of Xiaolangdi, the rapid increase in the transverse slope was effectively mitigated.