黑河下游颈口裁弯后河道三维水流结构研究

黄河源黑河下游于2018年7月汛期发生1次颈口裁弯的极端地貌过程,裁弯河段的水流结构发生强烈调整,开展原型观测裁弯后河道水流结构具有重要科学意义。2019年和2020年采用声学多普勒流速剖面仪对裁弯河段共计45个横断面进行野外测量,对比分析裁弯后河道三维水流结构与环流强度。结果表明:受河道形态、边界条件、水文条件等因素影响,裁弯口上游顺直河段的水流结构受颈口裁弯的影响较小,而弯道段水流结构于裁弯后明显调整。具体表现为颈口裁弯对顺直河段的流速、环流强度空间分布无较大影响,会改变弯顶段最大流速的横向分布和环流结构的断面分布、影响分离区的规模和分布位置。研究结果加深了颈口裁弯后水流结构调整对牛轭湖淤积、分离区河床冲淤以及新河道冲刷影响的认识。     

冲积性河流河床冲淤调整对洪水泥沙过程的响应——以黄河游荡型河段为例

为研究冲积性河流造床机理,基于能量耗散原理分析河床调整与水沙过程（变异特性）间的关系十分必要。以黄河游荡型河段为例,利用实测资料分析和平面二维水沙数值模拟方法,进行了各种洪水泥沙条件下河流冲淤规律的探讨。研究发现平滩面积、河相系数与径流泥沙特征值间存在的关联性映射出冲积性河流能量关系中的制约机制;不同洪水泥沙过程的河床冲刷强度变化具有阶段性,主槽累积刷槽效应与洪水泥沙过程有密切响应关系;高效输沙的洪水过程通过塑造最适宜的河床断面形态,能实现最佳输沙效率与主槽的最大冲刷。在不同漫滩洪水条件中,综合系数Φ最大时的洪水过程具有最大累积刷槽效应,因此对应流量可作为黄河下游漫滩洪水的调控指标。     

黄河大禹渡至稠桑河段裁弯流路及工程布置研究

黄河三门峡库区大禹渡至稠桑河段2002年发生自然裁弯后,河道长度缩短9km,为防止该河段再次形成"Ω"形河湾,维持或扩大自然裁弯的效果,减缓潼关高程的抬升,拟尽快开展河道治理,实施裁弯工程.本文详细介绍了裁弯工程流路及治导线规划方案.     

曲流串沟型江心洲形成机制与演化探讨

曲流串沟型江心洲是现代河流水利学研究关注的重要河流要素,不同于曲流河点坝和辫状河心滩,但在油气储层沉积学研究中鲜有关注。选取现代松花江典型河段,开展基于水动力学的沉积数值模拟,恢复曲流串沟型江心洲的演化过程,建立了曲流串沟型江心洲演化模式。研究结果表明:1）洪水期曲流河发生漫滩冲刷,串沟发育扩张,截弯取直,形成分汊河道及江心洲地貌;2）分汊偏移角、相对梯度优势可用于预测短期汊道存在的稳定性;3）串沟型江心洲形成于曲流点坝残余沉积之上,发育洲头侵蚀、洲尾加积、翼部双侧积,但垂向加积主要发育在顶部,不构成沉积主体结构。通过上述研究建立了曲流江心洲沉积模式,揭示了曲流河江心洲内部结构及分汊河道水动力特征,对现代河流治理和地下河流沉积储层刻画有指导意义。     

基于砾石群布置的河道生物栖息地自然化改造

为探讨砾石群对河道生物栖息地自然化改造效果,以江西金沙溪河段为例,采用文献调研和数值模拟的方法,选择鲢鱼为目标物种,耦合河段的平面二维水动力及栖息地模拟,研究了砾石群布置对裁弯河道生物栖息地的影响特性及自然化改造效果。结果表明:裁弯河道鲢鱼栖息地加权可用面积（A_WU）明显减少,弗劳德数在其主流线附近增大,剪切速度值由原河道的横向梯度分布转变为均匀分布;砾石群对裁弯河道生物栖息地的自然化改造效果显著,其中河道凹岸高密度布置方式使鲢鱼栖息地可用面积百分率（A_PU）由裁弯河道的9.20%增长至15.06%,砾石群下游附近水流的弗劳德数由裁弯河道的0.13~0.68骤降至0~0.15,砾石群下游区域形成低速水流区,为鲢鱼在大流量河道中提供了良好的庇护场所。     

基岩弯曲河段洪水水流结构的试验研究

低坡度基岩弯曲河流在地质构造控制区域广泛存在（床面坡度小于5‰）,洪水对基岩弯曲河流的河床淤积与侵蚀具有较大影响,但以往研究对基岩弯曲河流的洪水动力结构认识不足。通过几何概化基岩弯曲河段,考虑Froude相似与边壁粗糙,建立基岩弯曲河道概化模型,分析洪水下的弯道水面线分布、时均流场与湍流结构特性。结果表明:在洪水流量下,弯顶上游出现最小水面横比降、凸岸水流分离、凹岸双环流发育、流速下潜且二次环流强度达到最大,在弯顶下游水面横比降达到最大并出现环流分裂;床面切应力分布于凸岸水流分离以及弯顶上游中心区域,横向动量输移集中于弯顶上游。试验结果为基岩弯曲河道中的床面侵蚀与沿程淤积提供了水动力方面的解释。     

龙门山典型河流形态变化的潜在地震因素分析

以岷江支流白沙河和涪江支流湔江为例,探讨了2008年汶川地震之后龙门山地区河流形态的变化及其可能的长期构造地貌效应。研究表明,2008年汶川地震地表破裂带穿越河流形成裂点（跌水）,地震触发的山体滑坡、泥石流堵塞河道形成堰塞湖,致使河流形态及河流水动力条件随之发生变化。河流同震裂点在震后迅速消失,部分河段出现“裁弯取直”的趋势,这可能与河流中激增的沉积通量有关。随着周期性大地震的复发,河流的沉积-侵蚀过程会不断改变,伴随着震间活动断裂持续的构造变形,龙门山河流形态可能会发生快速变化。      

近400多年下荆江河段古河道演变过程及特征

为研究下荆江河段古河道演变过程及特征,利用20世纪30年代和50年代的历史地形图、1954年航片、1968年美国KH-4B军事卫星影像及2016年国产GF-1卫星影像,结合古籍资料,全面分析了下荆江古河道的演变特征并反演了其明万历年以来400多年的历史变迁过程.下荆江河段的古河道横向摆动频繁,受河道坚硬岸坡和人工护岸工程约束,空间上为20~32 km的古河道平面摆动带,形态上分为沿主泓线侧向渐变式摆动和河道突变迁徙两种古河道类型,它们是反演下荆江河段古河道的定位依据.历史上,下荆江塑造经历了漫流、支汊分流、单一顺直河道形成和曲流演化发展等复杂过程.明弘治年间,曲流主要出现在监利-城陵矶段,石首至监利段仅微弯;明末清初,东港湖弯道和濠河弯道均自然裁弯取直,下荆江蜿蜒型河道已全面上溯到石首境内,并形成了一系列河曲弯;19世纪中叶,下荆江的河曲发展突出表现在横向移动、河曲颈变窄、凹岸环流侵蚀后退、凸岸堆积淤高推进等特点.此后,下荆江没有出现大的变迁.下荆江河段近代河弯的演变模式有凸岸淤积推进、凹岸崩坍后退型,凸岸撇弯切滩、弯顶消减型和心滩漂移并岸、凹岸串沟过流型.河流的本身作用是其演变的主要原因,但人工修建大堤与大规模围垸是重要外因.      

波流作用下大直径淹没圆柱局部冲刷试验研究

水下大直径淹没圆柱在波流共同作用下的冲刷特性与非淹没情况有较大差别。在波流水槽中开展局部冲刷试验,将大直径淹没圆柱模型安装在中值粒径0.22 mm的平底沙床内,改变波浪波高和周期、水流流速和方向、圆柱淹没率,测量圆柱周围流速变化,记录柱周冲深发展历时,运用激光地形仪测量冲刷坑的地形形态,分析了淹没率S_r和相对高度h_c/D对准平衡冲深的影响。结果表明,相同入射波流条件下,随相对柱高h_c/D降低,冲刷发展速率、冲坑半径和深度都随之减小。当相对柱高h_c/D>1时,冲深随柱高增长速率较快直至达到临界值。准平衡冲刷坑呈"倒勺状",沿圆柱左右两边呈对称分布,柱前呈半环状;圆柱正后方淤积成"马鞍状"沙丘。     

无粘性土堤漫顶溃决水流运动试验研究

堤防溃决时溃口附近水流形态及溃决流量变化过程的正确描述是指导溃口堵复及时避险、预测溃堤洪水演进并进一步评估淹没损失的前提条件.通过弯道水槽中的概化模型试验,根据无粘性土堤防漫顶溃决的溃口变化和水流运动特征,将无粘性土堤防溃决过程分为漫流、冲槽、展宽及稳定4个阶段.试验系统研究了堤防溃决后河道以及溃口附近水位的变化过程,研究了河道洪水流量、洪水位和筑堤材料对溃口处水位的影响.基于大量的试验资料,进一步归纳总结出溃决流量与溃口口门宽度及溃口处水头变化之间的关系.     

Formation Mechanism and Sedimentary Pattern of Abandoned Channels

Accurately identifying and quantitatively describing abandoned channels in meandering rivers are of great significance for improving hydrocarbon recovery. By using modern deposition analogy, field outcrop analysis, a dense well spacing, core observations and a review of the literature, this paper studied the formation process and space–time amalgamation of abandoned channels in meandering river. The results reveal that formation mechanisms of abandoned channels include chute cutoff patterns(shoal-cutting, ditch-scouring and embayment-eroding patterns) and neck cutoff patterns. The chute cutoff pattern forms a gradually abandoned channel, while the neck cutoff pattern forms a suddenly abandoned channel. From upstream to downstream, the sedimentary pattern of the abandoned channel transforms from a chute cutoff pattern to a neck cutoff pattern, where the main controlling factors transition from the grain size and gradient to the flow and vegetation. An abandoned channel formed by a chute cutoff pattern consists mainly of siltstone, fine sandstone and thin gravel layers, which form a lithological-physical barrier. The abandoned channel formed by a neck cutoff pattern consists mainly of mudstone and argillaceous siltstone, forming a lithological barrier. Based on the amalgamation and structure of the reservoir architectural elements, the abandoned channel can be divided into three planar sedimentary patterns(crescent, semilune and horseshoe) for a single channel and five vertical sedimentary patterns for composite channels.     

长江重要堤防防渗与垂直防渗墙技术

历来长江中下游堤防洪水险情不断，堤基渗漏、堤身隐患、河岩崩塌是三大主要险情，而堤基渗漏尤其突出。本文阐述了堤基渗漏的地下渗流场，依渗流规律制定渗流控制措施，同时结合实际叙述了垂直防渗的主要措施－垂直防渗墙技术的多种工法。     

黄河济南以下河段某些异常地质作用及几种典型沉积构造研究

黄河自 1972年发生首次断流以来,以后 2 6年间,发生断流年数就有 19年,近年则愈演愈裂。由此引发了一系列特殊的地质作用,我们称之为异常地质作用,如汛期高含沙河水骤涨骤落,致使下游河床淤积严重,且不断抬高、展宽,并向二级悬河发育;床底不稳、河道迁移频繁,心滩、边滩上水道发育;而断流期则风的作用明显,风蚀地貌发育。水风地质作用混合,相克相伴,构成了黄河三角洲极为复杂的地质景观。又因黄河以沉积细粒物质为主,在多种因素的综合控制下,其沉积物层面或层内发育的沉积构造具有独特性,如变形层理、泥沙钟乳、液化 (泄水 )构造、气胀构造、植物划痕构造、特殊波痕及特殊流痕等,是典型的沉积构造。正确识别和分析黄河断流后的异常地质作用及由其形成的沉积构造对古河流相分析有重要参考意义.     

The response of the Lower Mississippi River to river engineering

An examination of the response of the Lower Mississippi River (LMR) to a variety of engineering activities is presented through the discussion of: (a) a brief history of engineering investigations and activities on the LMR; (b) the impact of artificial cutoffs on the channel geometry and water surface profiles of adjacent reaches; (c) the impact of channel alignment activities on channel morphology; and (d) the apparent impact of all of the LMR engineering activities on sediment dynamics in the channel.

Investigations by many agencies reflect over 150 years of study of the hydraulics and hydrology of the LMR, which have contributed significantly to our understanding of large alluvial rivers. In an effort to provide for flood control and navigation on the largest river in North America, private landowners and the US Army Corps of Engineers have performed a wide range of river engineering activities, including construction of levees, floodways, artificial cutoffs, bank revetment, training dikes, dredging, channel alignment, and reservoirs on the major tributaries. This unprecedented program of river engineering activities on the river during the last 100 years has resulted in the evolution of a freely meandering alluvial river to a highly trained and confined meandering channel. The LMR has increased its overall gradient and average top-bank width and generally increased its channel depth. The immediate response of the river to increased gradient as a result of the construction of artificial cutoffs was dampened in some locations by local geological controls.

Examination of the trends in sediment dynamics of the LMR reveals that the suspended load of the river has decreased during the 20th century. Conversely, a trend in the bed load transport in the channel for the years 1930 and 1989 cannot be determined with confidence because of the difficulty in acquiring representative samples. The highly trained river now responds to channel forming flows by attempting to build mid-channel bars rather than natural cutoffs of meanders.

The LMR should maintain a relatively stable plan form in the intermediate future, barring a very large and unprecedented flood. The river will continue to adjust its channel geometry and its local gradients as a response to variations in significant discharges. Continued channel maintenance and occasional dredging will insure the present state of sediment and water transport efficiency.     

The effects of removing bed materials on flow velocity (case study: Zaremrood River, Iran)

Nowadays, in parts of Iran, rivers and flood plains are being used as sand and silt mines, and the removal of river bed materials is performed without studying its effects on hydraulic behavior. On the other hand, the flood plain lands are in danger of floods and bank erosion. Zaremrood River in Tajan watershed due to removal of river bed material, two planes of before and after removal with scale of 1:1,000, has been used as basic data. The field investigation was emphasized on the end part of Zaremrood with a length of 5 km and starts from Ghandikola village to Ahoodasht Bridge. Using total station and field observations, the characteristics of reaches and cross sections of right bank, left bank, and main bed of river are written separately. Using software of HEC-RAS, ArcView 3.2, and extension HEC-GeoRAS, the flood zoning with different return periods to investigate water velocity and its changes, geometrical simulation of the bed, sides and flood way of rivers, and then by entering the results of HEC-GeoRAS into hydraulic software HEC-RAS for two before and after planes have been performed, and flow velocity was analyzed for three return periods of 10, 50, and 100 years. The results of this research showed that the velocities due to removal for floods with different return periods have increased, whereas water height and level during removal period have decreased.     

Sedimentology of the Upper Burdekin River of North Queensland, Australia—an example of a tropical, variable discharge river

The Burdekin River is an example of a class of tropical streams which experience two to four orders of magnitude variation in discharge, in response to seasonal but erratic monsoonal rainfall. Floods of the Burdekin rise abruptly, reaching peak discharges of up to 40,000 m³ s^-1 in less than 24 h; maintain peak flow for up to a few days, and recede exponentially. The geomorphology and deposits of these rivers reflect the extreme discharge fluctuations, and have not previously been described. A stretch of the upper Burdekin River comprising four bends and one straight reach was examined near the town of Charters Towers. The river bed is largely exposed for most of any year, with a small, misfit perennial channel carrying low stage flow. Major geomorphic elements of bends include point bars with ridge-and-swale topography, three distinct types of chute channels, avalanche slipfaces up to 5 m or more high around the downstream edges of bars, and on the outer part of one point bar an elevated, vegetated ridge. Straight reaches are flat or gently inclined, sand- and gravel-covered surfaces. Much of the river bed is covered by well sorted, in places gravelly, coarse to very coarse-grained sand with local accumulations of pebble to boulder gravel. Lower parts of the river bed are periodically draped by mud which is desiccated on exposure. Dunes and plane beds are the most commonly occurring bedforms, with local development of gravelly antidunes. Most bank tops and upper, vegetated bars are covered by silt and fine-grained sand. The river bed also hosts a low-diversity but locally high-abundance, flood-tolerant flora dominated by the paperbark tree Melaleuca argentea, which plays an important role in controlling the distribution of sediment. The gross geomorphology of the river bed and most of the sedimentary features are interpreted as having formed during major (bankfull or near bankfull) flows, which have a recurrence of about 18 years (based on 65 years hydrographic data). The initial rapid drop in discharge following flood peaks appears to preserve flood peak features on upper bars more or less intact, whereas lower areas are subjected to variable degrees of modification during falling stage and by more frequent, non-bankfull discharge events.     

长江中下游江湖关系演变趋势数值模拟

以长江中下游防洪系统为对象,概述了在大型复杂防洪系统洪水行为数值模拟基础上,成功地将长江中下游洪水演进数学模型转化为面向长江防洪系统防洪规划方案评估需求的长江中下游江湖水沙演变的数学模型.为适应防洪规划方案论证涉及江湖水沙相互制衡相互关联客观情况,建立了面向江湖水沙关系及其演变的数学模型.针对长江中下游江湖水沙运动特点,在水沙数值模拟的范围内侧重对下荆江河道冲刷、荆江三口分流分沙模式、洞庭湖泥沙淤积、江湖耦合等环节进行了讨论,提出了合理可行的数值处理方法.模拟结果较好反映了江湖水沙演变规律,主要成果已应用于长江中下游防洪规划和防汛调度方案中.     

枞阳长江干堤防渗墙截渗效果分析

综合分析了连续三年(特别是2002年汛期高水头作用期间)的安全监测成果,对枞阳长江干堤一标段水泥土防渗墙渗控效果作出了评价,揭示了长江水位与堤基渗透的变化规律。观测资料显示,汛期防渗墙前、墙后最大水位差为2.63 m,洪峰期间,部分监测断面防渗墙前堤基水位与江水位变化相关性较大,所有监测断面防渗墙后地下水位与江水位变化相关性较差,充分显示了水泥土防渗墙截渗效果。