Landslide dams constitute significant geological hazards, accompanied by challenges such as limited field data, urgent response requirements, and difficult mitigation conditions. This review systematically examines the topographic, hydrological, and geotechnical factors influencing dam formation and stability, highlighting the critical roles of material composition and internal structure in breach development. Existing methodologies for modeling dam-break scenarios, including statistical, parametric, simplified physically-based, and refined physically-based models, are critically evaluated, revealing persistent challenges such as parameter uncertainty, scale effects in physical experiments, and scarcity of field validation data. In addition, both engineering and non-engineering strategies for emergency response are reviewed. Key research gaps include an insufficient understanding of multi-phase interactions during dam failure, the potential for engineering interventions to alter failure modes (e.g., from overtopping to piping), the need for an improved dynamic risk assessment framework, and the integration of real-time data assimilation technologies. Finally, this review proposes future directions, including enhanced multi-source monitoring, machine learning-aided parameter inversion, uncertainty quantification and probabilistic forecasting, and improved dam-break models, to support effective decision-making in emergency scenarios.

The construction of large reservoirs has modified the process of water and sediment transport downstream, resulting in changes in the morphology of the river cross-section. Changes in water and sand transport and cross-sectional morphology are reflected in the rating curve at the cross-section. This study analyzed the variations in the rating curve at the Huayuankou (HYK) section and their influencing factors, and conducted water level predictions based on this relationship. The findings revealed that while the annual mean water level has shown a declining tendency over the past 20 years, the annual mean discharge has shown a constant pattern. The rating curve at this stretch narrowed from a rope-loop type curve in its natural condition to a more stable single curve as a result of the construction of the dam upstream of the HYK section. The effect of pre-flood section morphology and the water-sediment process on the scattering degree of the rating curve is inverse; increasing roughness and hydraulic radius decreases scattering degree, while increasing sand content and sand transport rate increases scattering degree. Using the measured data from 2020 as an example, the feasibility of predicting cross-sectional water levels using the rating curve was verified. The prediction results were accurate when the flow was between 1000 and 2800 m3/s; However, when the flow was between 2800 and 4000 m3/s, the forecast results were typically slightly lower than the measured values. Overall, the method demonstrates good predictive accuracy. Insight from the method can be used to predict water levels to better inform decision making about water resources management, and flood emergency response in the lower Yellow River.

As a prerequisite and foundation for studying the evolution mechanism of river channels, an in-depth understanding of the cross-sectional morphology adjustment is required. As a starting point, it is crucial to systematically summarize and generalize the research findings on channel morphological adjustment obtained to date, particularly in the context of the significant changes in the water and sediment conditions of large rivers that have occurred worldwide. This paper provides a comprehensive review of the research findings on the three following aspects of the Lower Yellow River: the transverse distribution of overbank flow velocity, the transverse distribution of suspended sediment concentration, and the morphological adjustment of the river cross-section. There are various equations available to predict the lateral depth–average flow velocity distribution. These equations are classified into the two following categories: empirical and theoretical formulas. Theoretical formulas are obtained through consideration of the cross-sectional morphology, accounting for inertial force terms caused by secondary flow, and momentum transfer between the main channel and its floodplain. Similarly, empirical equations and theoretical formulas for sediment concentration transverse distribution are also summarized, given the different influencing factors and assumptions. We also discuss the morphological adjustment of river cross-sections based on the analysis of measured data, mathematical model calculation, and the physical model test. In particular, we propose the idea of revealing channel cross-section morphology evolution mechanisms from the theoretical level of water and sediment movement and distribution. This review aims to enhance understanding of overbank flow, sediment transport, and channel morphology in the Lower Yellow River and may also serve to some extent as a reference for the evolution and management of channels in other rivers.

The key factor influencing flood evolution and the progression of riverbed erosion and silting in the wide floodplain of the Lower Yellow River (LYR) is channel roughness. The distribution law of channel roughness has changed since the implementation of water storage and sand control in Xiaolangdi Reservoir in 2002, and the change in roughness has had a number of effects on the design of flood control projects and ecological environment protection planning of the lower reaches. Manning's formula was used to calculate the roughness based on cross-section data and hydrological data collected by typical hydrological stations in the wide floodplain of the LYR from 2002 to 2020. The evolution law and influencing factors of channel roughness of typical sections before and after floods were also examined. The findings indicate that: (1) The post-flood roughness was slightly higher than the pre-flood roughness in the same area. The post-flood roughness in the Huayuankou and Sunkou sections significantly increased compared to the pre-flood roughness, with an increase rate of 14.64% and 19.37%, respectively. (2) The time-to-space variation of roughness in the wandering section exhibits a decreasing trend, whereas the time-to-space variation of roughness in the transition section exhibits a slightly increasing trend. (3) The channel roughness decreases with an increase in Froude number, but there is no clear relationship between the roughness and sediment content. (4) Using Huayuankou and Gaocun stations as examples, the channel roughness is inversely proportional to the flow, the average sectional velocity, and the cross-section area of the flow. The channel roughness of the wandering section is inversely proportional to the ratio of width to depth, and the channel roughness of the transition section is proportional to the ratio of width to depth. Roughness and average velocity were determined to have the best-fitting connection, with R2 values of 0.62 and 0.78, respectively. (5) The main elements impacting channel roughness in the wide floodplain of the LYR are section shape and flow condition.

黄河下游滩区是一个复杂的互馈系统,系统的安全及协调发展关系到一个地区的稳定与可持续发展.为科学评价黄河下游典型滩区社会经济-防洪安全-生态环境耦合系统的安全发展水平与协调程度,明确影响其发展趋势的主要原因.针对黄河下游兰东滩区的区域特征,综合考虑社会经济、防洪安全、生态环境对滩区发展的影响,遵循指标选取的诸多原则,通过组合权重法确定指标体系权重,构建了黄河下游兰东滩2001-2020年的耦合协调度模型,对耦合协调度变化趋势进行分析预测.结果表明:①黄河下游兰东滩区社会经济-防洪安全-生态环境耦合系统相互作用明显,但整体协调耦合发展程度不高,距离优质协调还有一定的差距;②综合系统的耦合度与耦合协调度拟合优度较好,均在0.9以上,且其趋势线与防洪安全评价指数趋势较为接近,表明防洪安全对综合系统的影响较大;③组合权重占比较大的主要是防洪安全方面的指标,其次是社会经济,最后是生态环境,表明兰东滩安全发展与环境友好的前提就是保障最基本的防洪安全;④3个子系统的安全评价指数在近20年都有不同程度的增幅,社会经济子系统安全评价指数稳定上升,增长速度明显高于防洪与生态,防洪安全与生态环境子系统发展较为不均衡.

Landslides often occur in V-shaped valleys exhibiting strong river incisions and large elevation differences between the riverbed and surrounding mountains. This study expounded upon the topographical and flow conditions of typical landslide dam sites through field investigations and data collection and established a small-scale physical model for experimental research. The formation conditions of landslide dams, an important part of the long-term management of such events, were studied. Simultaneously, the experiments verified a series of engineering measures proposed based on calculus theory and implementation principles according to their experimental disposal effects to mitigate short-term flood risks. Results showed that the dam formation is mainly related to topographic characteristics, upstream flow, and dam compositions. Specifically, steep V-shaped valleys should be considered when establishing physical models as they provide great conditions for landslide mass blocking the river completely. In addition, for earth dams, the effects of the position and direction of excavated diversion channels were compared; it showed that when there are multiple passes on the dam crest, priority should be given to lateral excavation of channels from the pass to restrict the lateral development process. The dam-break flow direction should better be orthogonal rather than be parallel to the river bend, which can reduce peak flow discharge by natural energy dissipation. For earth and rockfill dams with wide particle distributions, piles and flexible nets were instead utilized to coarsen the dam breach and reduce peak flow discharge. Finally, applicable values and research significance were summarized based on the obtained results. This research enriches studies of mountain disaster management and provides guidance for on-site emergency response.

2021年黄河发生了新中国成立以来最严重的秋汛,在深入推动黄河流域生态保护和高质量发展的关键时期,基于此次秋汛典型河段归纳与总结黄河下游防汛抗洪抢险行之有效的实践经验十分必要.以位于黄河"豆腐腰"的开封河段为研究对象,基于上游水文站实测水文数据及局部河段水下地形资料,在分析2021年秋汛洪水特征的基础上,总结了开封河段成功防御大流量、长历时、高水位洪水的实践经验.研究提出的"一二三四五"防汛工作基本原则、"党政领导、应急统筹、河务支撑、部门协同、群防群控"防汛抢险机制、黄河滩区迁安救护四类安置新方法等,不仅可为未来黄河防汛工作提供支撑,也具有可复制、可推广性,对其他河流治理有借鉴意义.

为探究气候变化与人类活动影响双重作用下黄河入海水沙新情势,基于1950-2018年利津站实测水沙资料,采用系列水文检验方法,从趋势性、变异性、年内分布和水沙搭配四个方面系统分析了黄河口来水来沙变化规律.研究发现,黄河口水沙情势变化显著,主要包括:黄河口水沙通量总体均呈显著减少趋势;水沙均在1985年前后发生变异,其变异时间与水库的修建和运行密切相关;水沙年内分布发生了变化,1950-1999年水沙大量入海集中在8-10月,年内分布不均匀度呈增大趋势,2000年以后主要集中于6-7月的调控期,年内分布不均匀度稍减;来沙系数2000年以前逐阶段增大,2000年后锐减至自然阶段水平,且最大水流挟沙力对应流量呈减小趋势.总体来看,黄河口来水来沙过程逐渐由自然模式转变为人为调控模式.

下游滩槽综合治理是黄河综合治理实践中存在的突出问题之一.在分析近期黄河流域水沙情势的基础上,采用实测资料系统分析了黄河水沙调度效果,并提出了未来黄河下游滩槽综合治理思路.研究表明:近期黄河流域水量偏多,编号洪水出现频次增加,通过水库群联合调控保障下游防洪安全势在必行;黄河水沙调度在调节洪水流量过程、库区排沙以及减少下游河道淤积方面效果显著;按照现有控导工程连线修建一定标准二级堤防,将滩区划分为主行洪区和滞洪沉沙区,并通过科学管理控制不同区域滩地糙率系数,可实现既能保证大洪水安全过洪,又能为过洪机率较低区域提供经济发展空间的治理目标.研究成果可为黄河下游"滩-槽"协同治理提供参考.

Approximately 90% of the sediment yield of the Yellow River is derived from the Loess Plateau. In this paper, the Loess Plateau was used as the research object. To investigate the influence of economic and social development on reducing sediment load of the Yellow River, a mathematical method was employed with hydrological and sediment data from three hydrological stations (Toudaoguai and Sanmenxia at the Yellow River, and Ganguyi at the Yan River) as well as per capita GDP data from the Yan River basin. The results showed that the reduction in runoff in the reaches between the Toudaoguai and Sanmenxia stations accounted for 39.3% of the decrease in the sediment load of the Yellow River, and the other 60.7% of the decrease may have resulted from economic and social development. Using the Yan River basin as an example, there was an inverse relationship between per capita GDP and sediment delivery during the period from 1984 to 2018. Grey relational analysis revealed a relatively high relation between the sediment load of the Yan River and the number of rural laborers transferred from the area, the afforestation area, and the tertiary industry value of Yan'an city. Thus, economic development and social transformation are highly related to sediment delivery in the basin, which may result in a decrease in sediment delivery to some extent.

Barrier lakes are secondary disasters with associated landslides and debris flow that can cause serious damage to the downstream populations and areas. Existing studies are lacking in comprehensive descriptions of the rescue process, where the main channel streamflow varies and topographic erosion develops, as well as engineering disposal performs. This paper aimed to theoretically investigate the formation and emergency responses to barrier lakes using on-the-spot investigation and calculus theory. The results showed that the formation of a barrier lake led to a sudden variation in the flow-change rate (normal to infinite). However, after implementing emergency measures, this rate returned to normal. The whole rescue process could be regarded as the accumulation of disposal effects. Volume changes in the main streams were expressed by a differential equation of the lake surface area and water level variations. In addition, a corresponding theoretical description of flow discharges was also given when engineering measures such as the excavation of diversion channels and engineering blasting were adopted. Specifically, the theoretical expressions of flow discharge were given respectively in the developing stage and breach stable stage after the excavation of diversion channels. The flow discharge through certain sections was also described theoretically when engineering blasting was chosen to widen and deepen the cross-section of the diversion channels. Overall, this paper mathematicizes and theorizes the existing emergency measures, which helps to better understand their implementation principles and application requirements.

对黄河河口入海流路的稳定类型进行分类整理和概括总结,简要回顾其人工改道标准阈值的演化和确定过程,初步构建入海流路实施改道的阈值体系,利用实测资料对典型流量级改道水位阈值、河长阈值、海域容沙阈值及其河口容许累计来沙量阈值进行了论证分析和计算.结果表明:现状流量为3000 m3/s的改道水位阈值为10.58 m,河长阈值约为89 km,海域容沙阈值约为72.19亿m3,相应的利津站累计来沙量阈值约为120.65亿t.

对黄河河口现行清水沟流路范围内不同汊河的形成、演化及其特征进行了梳理总结,围绕汊河不同运用方案的影响效应进行了论证分析.研究表明:现行清水沟流路范围内的汊河运用方案不适用于多汊河轮流行河模式、同时行河与轮流行河联合模式和同时行河模式,而采用单一汊河轮流行河模式可以充分发挥海洋输沙动力,保证河口海域向外海的较大输沙量,对延长清水沟流路使用年限更有利,更为科学和经济合理.在现行清8汊河达到改道标准后,应优先使用老河道汊河,该方案不仅有利于未来海岸线的均衡发展,而且更有利于延长清水沟流路的使用年限.

The evolution of channel bars in response to upstream damming has significant impacts on channel stability, navigation, and aquatic habitats. Here, the effects of the Three Gorges Dam (TGD) operation on downstream channel bars in the Yichang-Chenglingji Reach (YCR) were comprehensively analyzed using remote sensing images, cross-sectional profiles, and hydrological datasets. The morphodynamic adjustments of channel bars in the YCR were significantly different during the pre- and post-TGD periods (i.e., before and after the construction of the TGD). Specifically, the total area of channel bars did not exhibit any significant trend in the pre-TGD period, but displayed a significant reduction following the construction of the TGD, although the morphodynamic response of each sub-reach was different. The channel bars in the YCR were relatively stable in the pre-TGD period, but became more erodible in the post-TGD period. The length/width ratio (LWR) of the bars showed an overall increase trend during the whole period from 1992 to 2017, not changing before and after the dam construction. The water discharge that led to the greatest channel bars adjustment was 27,000-30,000 m(3)/s (corresponding to bankfull discharge) in the pre-TGD period and 15,000-18,000 m(3)/s (corresponding to the medium discharge that can submerge the surface of the bars) in the post-TGD period. In addition, the grain size of non-uniform sediment with the highest replenishment degree gradually reduced downstream; these finer sediments were the main sources of material for the channel bars in the YCR. Quantitative relationships between bars area, the most effective bar-forming discharge and suspended sediment load with the highest replenishment degree, were proposed based on the improved Delayed Response Model (DRM). Results indicate that geomorphic adjustments of channel bars in the YCR are closely related to the previous four-year flow and sediment regimes, implying a delayed response of the fluvial system to damming.

Delta channels are important landforms at the interface of sediment transfer from terrestrial to oceanic realms and affect large, and often vulnerable, human populations. Understanding these dynamics is pressing because delta processes are sensitive to climate change and human activity via adjustments in, for example, mean sea level and water/sediment regimes. Data collected over a 40‐year period along a 110‐km distributary channel of the Yellow River Delta offer an ideal opportunity to investigate morphological responses to changing water and sediment regimes and intensive human activity. Complementary data from the delta front provide an opportunity to explore the interaction between delta channel geomorphology and delta‐front erosion–accretion patterns. Cross‐section dimensions and shape, longitudinal gradation and a sediment budget are used to quantify spatial and temporal morphological change along the Qingshuigou channel. Distinctive periods of channel change are identified, and analysis provides a detailed understanding of the temporal and spatial adjustments of the channel to specific human interventions, including two artificial channel diversions and changes in water and sediment supply driven by river management, and downstream delta‐front development. Adjustments to the diversions included a short‐lived period of erosion upstream and significant erosion in the newly activated channel, which progressed downstream. Channel geomorphology widened and deepened during periods when management increased water yield and decreased sediment supply, and narrowed and shallowed during periods when management reduced water yield and the sediment load. Changes along the channel are driven by both upstream and downstream forcing. Finally, there is some evidence that changing delta‐front erosion–accretion patterns played an important role in the geomorphic evolution of the deltaic channel; an area that requires further investigation. © 2020 John Wiley & Sons, Ltd.

Qingshuigou channel, a recent river at the Yellow River Delta(YRD), has been flowing for more than four decades since 1976. The evolution of the Qingshuigou channel and its stability are related to the development of the YRD area. Based on previous studies, a time-based determination index of water and sediment collocation was proposed in this paper according to the data of water and sediment discharges at the Lijin Station from 1976 to 2015. The Qingshuigou trail channel morphology adjustments were analyzed according to the cross-sectional measured data, and then the volumes of scouring and silting in the channel were calculated as well. The results showed that the geomorphic adjustment processes of the Qingshuigou channel could be divided into four different phases: Phase Ⅰ-rapid deposition of beach trough, Phase Ⅱ-blanking and widening of main trough, Phase Ⅲ-silting and shrinking of main trough, and Phase Ⅳ-narrow-depth development of main trough. Commonly used reference indexes for river diversion, such as the ratio of horizontal to vertical gradients, and the dimensionless difference of beach to trough, were applied to evaluate the characteristics of channel diversion risk along time and space of the Qingshuigou channel. It was indicated that the channel reaches close to Q7 were the most prone to diversion by the end of Phase Ⅲ. Based on the delayed response model, the estimating method of the river longitudinal gradient evolution trend was established. The simulation results demonstrated that the longitudinal slope of the Qingshuigou channel had reached the equilibrium value by the end of Phase Ⅳ.

As rivers approach base level, their water and sediment dynamics are affected by a transitional reach known as the backwater zone. At low flows, backwater zones cause flow deceleration and in-channel sedimentation, but at high flows, they cause flow acceleration and erosion. Over many floods, the dynamics of deposition and erosion in the backwater zone are thought to control the locations of avulsions on some large deltaic channels. However, in various studies, the role of the backwater is often inferred or modeled, and directly observed evidence of how backwater affects channel dynamics at avulsion sites remains scarce. In this study, we show how the backwater zone impacts the evolution and avulsion of the Qingshuigou channel, a recent lobe on the Yellow River Delta, using four decades (1976-2015) of data from systematic surveys of water discharge, sediment load, cross-sectional profiles and water surface elevation. The results show that the channel was commonly eroded during flood seasons and aggraded during nonflood seasons. Erosion rates generally decreased in the downstream direction along the lower channel reach during flood seasons, primarily due to downstream channel widening and the subsequent decrease in sediment transport capacity. The erosion rate reached zero at the cross-sections farthest downstream, which is contrary to expectations under hydrodynamic backwater effects, where drawdown causes erosion to increase downstream during high flows. During nonflood seasons, maximum sedimentation occurred upstream of the backwater zone, possibly due to impacts of local topography of meandering bends or constriction from dikes. Morphodynamic backwater accompanied by the deposition and gradual progradation of a mouth bar resulted in downstream increasing sedimentation, superelevation, and lateral migration rates along the lower channel reach from 1985 to 1996. The predicted avulsion location was near cross-sections Q6 or Q7 with an avulsion length of similar to 20-30 km upstream of the shoreline, which was consistent with those for historical avulsions. We emphasize the close interplay between backwater effects and channel geometry and argue that morphodynamic backwater may play a more important role than hydrodynamic backwater in setting up and triggering avulsions on the Yellow River Delta. (C) 2019 Elsevier B.V. All rights reserved.

为探讨人类活动对黄河口流路演变的影响,以清水沟及刁口河流路为研究对象,采用实测资料分析方法,对比分析了两流路1964-2015年水沙条件及河道横、纵、垂向几何形态及冲淤变化.研究表明:两流路演变过程均具有阶段性,改道初期,发生大范围的快速淤积;改道中期维持的时间往往与水沙条件的变化有关,若水沙条件较好,则河道淤积减缓甚至发生冲刷,若水沙条件较差,河道演变迅速由中期转至后期;改道后期,河道迅速萎缩,滩唇淤高,横比降增大,形成地上悬河,地上悬河的形成标志着下一次改道即将丌始.清水沟第Ⅳ阶段受清8改汊和调水调沙影响,主槽冲深,河道相对稳定.

The avulsion time scale of channels on the Yellow River delta (YRD) is about a decade due to the large sediment load, and rapid channel aggradation and progradation. Nevertheless, the Qingshuigou channel has been maintained for about four decades since 1976. This channel provides an ideal opportunity to study channel evolution following avulsion and to examine different avulsion criteria. In this study, we analyzed the geomorphic adjustment of the lower Qingshuigou channel during 1976–2015, and calculated normalized gradient advantage and superelevation at the channel to estimate how close the channel was to avulsion. Results showed that channel evolution processes may be divided into four phases: I (1976–1980) rapid aggradation, II (1980–1985) channel widening and enlargement, III (1985–1996) main channel aggradation and shrinkage, and IV (1996–2015) main channel incision and deepening. Evolution phases I, II and III are similar to the avulsion cycle observed in natural and experimental fluvial systems. The calculated values of normalized gradient advantage and superelevation in early 1990s exceeded the critical values suggested by previous studies, implying that the channel was prone to avulsion. Nevertheless, avulsion was prevented mainly due to limited overbank flows, constriction from artificial dikes, and slowed channel extension as a result of reduced sediment load. The evolution of the Qingshuigou channel confirms previous arguments that superelevation and gradient advantage are not sufficient for avulsion, and multiple factors should be considered, including flood frequency, lateral mobility, sediment diameter, and human interruptions.

In order to determine the relationships between the length of estuarine reach and the flow and sediment regime,the methods of the field data analyses were used in this study.The changes in flow and sediment conditions at Lijin and the length of estuarine reach were analysed during 1954-2012,and it is discovered that there was a decrease in water volume and sediment load during 1954-2002,but after 2002 the water volume and sediment load increased relatively owing to the operation of Xiaolangdi Reservoir.In addition,every time after channel avulsion at the Yellow River estuary,the river length downstream of the diversion point was suddenly shortened and then it increased with a decreasing rate;moreover,the rate of increasing was reduced evidently caused by the effects of human activity in recent years.Different empirical formulas for the length of estuarine reach of the Yellow River were established by taking different factors (single factor:cumulative sediment amount,incoming sediment coefficient) into account during different periods and the whole period.The proposed formulas are simple in form and the calculated data agreed generally with the measured data;therefore these formulas are applicable to the calculation and prediction of the length of estuarine reach,so as to provide references for studying the channel evolutions of the Yellow River estuary.