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The Yellow River is usually assumed to record tectonic activities and climatic changes; however, a systematic study was lack in the sedimentology, stratigraphy, geomorphology and geochronology for the entire Yellow River though various geologic scholars have conducted numerous works in individual basins. This review focused on well-preserved fluvial terrace sequences that formed along this river on northeastern (NE) Tibetan Plateau and Ordos Block over the past 2.6 Ma. After comparing numerous initial incision ages at different segments along the Yellow River, we found out that the youngest initial incision may occur at ca. 150 ka at the Longyang Gorge. The Yellow River may transit from multiple separated endorheic drainages to an entire external drainage after 150 ka, which may cause differentiations in the apparent incision rates before and after 150 ka; thus apparent net incision rates were calculated respectively for the Yellow River before 150 ka and the drainage network post 150 ka. Apparent net incision rates prior to 0.15 Ma were calculated as 0.15, 0.29, 0.10, 0.12 and 0.03 mm/a respectively in Tongde-Xunhua, Lanzhou-Linxia basins, Heishan, Jinshan and Fenwei-Sanmen Gorges in this review, which mainly reflected Kunhuang-Gonghe Tectonic Event, generated by the Indo-Asian collision and diminishing as the NE Tibetan Plateau eastward extruding at ca. 1.8–0.15 Ma. Apparent net incision rates post 0.15 Ma were calculated respectively for NE Tibetan Plateau and Ordos Block, considering their different base level. On NE Tibetan Plateau, four fluvial degradational phases were identified between ca.105∼70, 53∼40, 25∼16 and 12∼6 ka associated with terrace levels respectively, at average elevations of 96, 40, 20 and 10.5 meters above the current river level (m arl) within a range of 5 ∼ 96 m arl; and four broad periods in the last 150 ka on Ordos Block: possibly marine oxygen isotope stage (MIS) 5, ca. 118 to 72 ka, most of MIS 3, ca. 44∼28 ka, transition from LGM to last deglacial ca. 20 to 16 ka, and 4∼3 ka at average elevations of 67.5, 26, 19 and 11.5 m arl. These degradational phases post 0.15 Ma were associated with multiple processes including enhanced fluvial discharge with an increase in monsoonal precipitation and/or melt water in deglaciation. [ABSTRACT FROM AUTHOR]

Artificial chute cutoff can fundamentally eliminate the threat of flood caused by the meandering river, but it significantly changes its morphodynamic characteristics. Channel adjustments after cutoff are rapid, which makes it difficult to study the interaction between river morphology and flow structure only through field measurement. However, numerical simulations can provide insights into the hydrodynamic characteristics after artificial chute cutoffs. In this study, both field measurement and numerical simulation are employed to investigate the flow structure and bed morphology caused by an artificial chute cutoff in Sipaikou area of the Upper Yellow River in 2018. The measured hydrological data provide boundary conditions and initial values for the numerical model. The field measurement results reveal that the concave bank of the study area is severely scoured up to 270 m after the artificial cutoff, and a 20 m deep scour hole and a 2.26 km long pool are formed at the entrance and near the left bank of the chute channel. The numerical simulation results of velocity at typical cross-sections are in good agreement with the measurement results. Flow separation and stagnation zones are observed near the right bank during the low flow conditions (discharge of at least 902 m3/s), but this phenomenon is not seen during larger flow conditions (discharge exceeds 2000 m3/s). Interestingly, flow recirculation zones are also found near the left and right banks of the scour hole. Further, a long flux belt is formed at the scour hole and the pool. Consequently, the impact of the bed topography on the hydrodynamic characteristics is relatively prominent when the discharge is small, while the impact on the river banks and river bed is more noticeable when the water discharge is large. In addition, high shear stress is observed near the left bank at the downstream of the studied area, which indicates that the left bank at the downstream is still being scoured. These results suggest that bank protection measures along the left bank are required to maintain the effectiveness of the artificial chute cutoff. [ABSTRACT FROM AUTHOR]

Mapping and assessing soil-erosion risk can address the likelihood of occurrence of erosion as well as its consequences. This in turn provides precautionary and relevant suggestions to assist in disaster reduction. Because soil erosion by water in the watershed of the Ningxia-Inner Mongolia reach of the Yellow River is closely related to silting of the upper reaches of the Yellow River, it is necessary to assess erosion risk in this watershed. This study aims to identify the soil-erosion risk caused by water in the watershed of the Ningxia-Inner Mongolia reach of the Yellow River from 2001 to 2010. Empirical models called Chinese Soil Loss Equation (CSLE) and Modified Universal Soil Loss Equation (MUSLE) were used to predict the erosion modulus in slope surfaces and gullies. Then the soil erosion risk in this watershed was assessed according to the classification criteria of soil erosion intensities (SL190-2007). The study results showed that the range of values of the erosion modulus in this watershed was 0-44,733 t/km/a. More than 20% of the total watershed area was found to present an erosion risk, with the regions at risk mainly located in channels and their upper reaches, and in mountainous areas. To determine the regression coefficients of the erosion factors with respect to erosion modulus, a GWR (geographically weighted regression) was carried out using the ArcGIS software. It was found that the topographic factor has the highest contribution rate to the soil erosion modulus, while the highest contribution rate of the erosion factors to the erosion modulus and the largest values of the factors were not located in the same places. Based on this result, the authors propose that slope management is the most important task in preventing soil loss in this watershed, and the soil-conservation projects should be built according to the contribution rate of the erosion factors. [ABSTRACT FROM AUTHOR]