黄河游荡河段河床形态调整对洪水过程的响应

以黄河流域1950～1985年200余场洪水资料为基础，并增加了最近的实验资料，分析了黄河下游游荡河段不同含沙量沙水过程中河床形态的调整过程，结果表明，由洪水过程所导致的河床形态变化是相当剧烈的。且与含沙量密切相关，表现出非线性的变化规律，当含沙量较小时，随含沙量的增大，洪水后河床宽深比增大，当含沙量增大到一定程度后再增大时，宽深比随含沙量的增大而减小，这一结果为修正Schumm关于河床形态变化的定性预测关系提供了新的依据。     

三峡水库下游弯曲河型演变规律调整及其驱动机制

大型水库的兴建深刻改变了下游水沙输移特点,进而导致河床演变规律显著调整,水库下游弯曲河型对水沙过程改变响应敏感,是水库下游河床演变、航道整治、河势控制等方面研究的关键区域。本文基于1996-2016年的实测水文、地形资料,对长江三峡水库下游弯曲河型的演变规律及其驱动机制开展研究,结果表明：① 三峡水库蓄水前,下荆江存在“凸淤凹冲”、“凸冲凹淤”两类弯曲河型,而三峡水库蓄水后均表现为“凸冲凹淤”的一致性规律;② 在水库拦沙作用的影响下,下荆江河段平滩河槽存在累积性冲刷现象,冲刷部位集中于枯水河槽与基本河槽之间的低滩,冲淤部位调整主要由变化的流量过程所驱动,上游河势、河道边界以及支流入汇等因素均有一定驱动作用;③ 在三峡水库蓄水后缺乏大洪水的情况下,凸岸水流挟沙力随流量增加逐渐增强,水流对凸岸冲蚀力度在平滩流量级附近（20000~25000 m3/s）达到最强,平滩流量附近流量级的持续时间超过20天时,弯曲河道发生凸冲凹淤现象。而悬沙中造床粗沙的减少,增强了水流冲刷强度,加剧了凸岸的冲蚀程度。     

Channel Bed Mobility Downstream from the Elwha Dams,Washington*

Dams are a major source of fragmentation and degradation of rivers. Although substantial research has been conducted on the environmental impacts of large structures in the United States, smaller dams have received less attention. This study evaluated the impact of two dams of moderate size, the Elwha Dams, on the downstream channel system using field data collection at river cross‐sections. The relationship of average boundary shear stress (τ_o) to critical shear stress (τ_cr) served as the basis for determining channel bed material mobility under the two‐year and ten‐year flood events. The channel had the greatest channel bed mobility at the natural cross‐section upstream from the dams, low bed mobility between the structures, and an increase in channel bed mobility in the low gradient river segment near the mouth of the river. Low bed mobility tended to be associated with a lack of channel system complexity, including reduction or loss of bars and low alluvial terraces and their associated young riparian communities. Although these run‐of‐the‐river dams do not modify streamflow greatly, the loss of sediment from the channel system has had a substantial impact on bed mobility and geomorphic and biotic complexity of the Elwha River.     

黄河中游马莲河历史与现代洪痕沉积与水文学研究

通过对马莲河流域深入调查研究,在马莲河下游峡谷峭壁发现了一组4个显著的洪痕。洪痕沉积物分析看出,马莲河洪水悬移质泥沙以粉沙为主,粘粒和沙粒含量都较低,磁化率值也很低。将这些数据与流域内马家原剖面黄土土壤的的分析结果对比,可知马莲河现代洪痕沉积物是暴雨洪水对于流域内黄土和土壤侵蚀、搬运沉积形成。采用面积－比降法对该组洪痕所记录的4次洪水事件进行了洪峰流量恢复计算。表明高于常水位3.3 m、5.5 m、6.7 m洪痕洪峰流量分别为1 170m³/s、4 060 m³/s、5 690 m³/s。它们与雨落坪水文站观测2005、2003、1977年的洪水洪峰流量值相当,误差小于5 %。最高洪痕高出常水位10～12 m,计算恢复其洪峰流量为13 980 m³/s,洪水发生年代为1841年（清代道光21年）。这些研究结果对于马莲河流域的防洪减灾、水利水电工程设计和水土流失防治具有重要科学意义。     

Morphodynamics of a pseudomeandering gravel bar reach

A large number of rivers in Tuscany have channel planforms, which are neither straight nor what is usually understood as meandering. In the typical case, they consist of an almost straight, slightly incised main channel fringed with large lateral bars and lunate-shaped embayments eroded into the former flood plain. In the past, these rivers have not been recognised as an individual category and have often been considered to be either braided or meandering. It is suggested here that this type of river planform be termed pseudomeandering.A typical pseudomeandering river (the Cecina River) is described and analysed to investigate the main factors responsible for producing this channel pattern. A study reach (100×300 m) was surveyed in detail and related to data on discharge, channel changes after floods and grain-size distribution of bed sediments. During 18 months of topographic monitoring, the inner lateral bar in the study reach expanded and migrated towards the concave outer bank which, concurrently, retreated by as much as 25 m. A sediment balance was constructed to analyse bar growth and bank retreat in relation to sediment supply and channel morphology. The conditions necessary to maintain the pseudomeandering morphology of these rivers by preventing them from developing a meandering planform, are discussed and interpreted as a combination of a few main factors such as the flashy character of floods, sediment supply (influenced by both natural processes and human impact), the morphological effects of discharges with contrasting return intervals and the short duration of flood events. Finally, the channel response to floods with variable sediment transport capacity (represented by bed shear stress) is analysed using a simple model. It is demonstrated that bend migration is associated with moderate floods while major floods are responsible for the development of chute channels, which act to suppress bend growth and maintain the low sinuosity configuration of the river.     

The characteristics of dike-break flood in different scenarios of the lower Yellow River based on numerical simulations

The lower Yellow River still faces the threat of flood due to the unusual precipita-tion caused by global environmental change, river channel sedimentation, hidden danger in the dike and unfavorable river regime of “hanging river”. According to the characteristics of the dike-break flood of the Yellow River, this paper has simulated, in six different scenarios, the dike-break flood routing by inputting the terrain data, typical historical flood data and land use data of study area to two-dimensional unsteady flow model. The results show that: firstly, the routing process of flood will occupy other rivers on the way and return to the rivers after reaching the lower reaches; secondly, in the same river reach, flood inundating area of north band is bigger than that at corresponding location of south bank under the same historical flood; thirdly, it is different in the degree of flood inundation in different regions due to different geographical locations in flood plain; fourthly, the area of mainstream where flood is deep and flow velocity is quick is relatively smaller, but the area of non-mainstream, where flood is shallow and flow velocity is slow, is relatively big; and finally, the possible influenced area of the dike-break flood is 141,948 km2.     

Prediction of alluvial channel pattern of perennial rivers

Purely braided, meandering and straight channels can be considered as end-members of a continuum of alluvial channel patterns. Several researchers have succeeded in separating channel patterns in fields defined by flow related parameters. However, the discriminators of the principal channel patterns derived from these diagrams all require some a priori knowledge of the channel geometry. In this paper a method is presented which enables prediction of the equilibrium conditions for the occurrence of braided and high sinuosity meandering rivers in unconfined alluvial floodplains. The method is based on two, almost channel pattern independent, boundary conditions: median grain size of the river bed material, and a potential specific stream power parameter related to bankfull discharge or mean annual flood and valley gradient. This can be regarded as a potential maximum of the available flow energy corresponding to the minimum sinuosity condition, P = 1. Based on an analysis of 228 datasets of measurement sites along rivers from many parts of the world an independent discriminating function was found that separates the occurrence of braided rivers and meandering rivers with P > 1.5. The function applies to equilibrium conditions of rivers that neither incise nor show rapid aggradation, with a bankfull or mean annual flood discharge above 10 m³/s and a median bed material grain size between 0.1 and 100 mm.     

黄河下游河道断面形态参数变化及其水沙过程响应

基于1965—2015年黄河下游花园口、高村、泺口站的逐年水文和汛前河道断面的实测资料，分析了河道断面形态参数（河道断面面积，河道宽深比等）的变化，以及对河道断面形态与来水来沙间的关系做出定量化分析。结果表明：主槽断面形态参数与水沙搭配以及前期断面形态密切相关，沿程3个断面形态参数调整方式存在显著差异。河宽调整幅度沿程减小，辫状河段变幅最大，尤其在1986—1999年，辫状河段萎缩程度最为严重，其次为弯曲河段，顺直河段横向调整幅度最小。受到前期断面形态的影响，辫状河段河道断面调整方式既有横向展宽（萎缩）又有垂直加深（淤积）；弯曲河段河道宽深比与流量呈较弱的正相关关系，具有横向和垂向的调整方式；而顺直河段的宽深比与流量呈负相关关系，与来沙系数呈正相关关系，河道以垂直加深（淤积）为主。     

The kinematics and pattern of escarpment retreat across the rifted continental margin of SE Australia

Rifted continental margins generally display an interior, low-relief, highly weathered upland area and a deeply incised, high-relief coastal area. The boundary between the two zones is commonly demarcated by an abrupt, seaward-facing escarpment. We investigate the rate and pattern of escarpment erosion and landscape evolution along the passive margin of south-east Australia, in the region of the New England Tableland. The process of rifting is shown to initiate an escarpment across which rivers flow, resulting in an escarpment that takes the form of dramatic, elongated gorges. Using a mass balance approach, we estimate the volume/unit length of continental material eroded seaward of the escarpment to be between 41 and 68 km², approximately an order of magnitude less than the 339 km² of terrigenous sediments calculated to have been deposited offshore, but consistent with earlier denudation estimates based on apatite fission track data. On the bedrock rivers draining the New England Tableland region, the escarpment is manifested as a series of sharp knickpoints punctuating the river longitudinal profiles. The knickpoints are situated the same distance upstream along the different channels and uniform escarpment retreat rates on the order of 2 km Myr⁻¹ are estimated, despite some differences in bedrock lithologies. Gorge head migration appears to be very important as a bedrock incision mechanism. Field observations indicate a coupling between escarpment retreat and knickpoint propagation, bedrock channel incision, and hillslope development.     

Anabranching in mixed bedrock-alluvial rivers: the example of the Orange River above Augrabies Falls, Northern Cape Province, South Africa

Anabranching is characteristic of a number of rivers in diverse environmental settings worldwide, but has only infrequently been described from bedrock-influenced rivers. A prime example of a mixed bedrock-alluvial anabranching river is provided by a 150-km long reach of the Orange River above Augrabies Falls, Northern Cape Province, South Africa. Here, the perennial Orange flows through arid terrain consisting mainly of Precambrian granites and gneisses, and the river has preferentially eroded bedrock joints, fractures and foliations to form multiple channels which divide around numerous, large (up to 15 km long and 2 km wide), stable islands formed of alluvium and/or bedrock. Significant local variations in channel-bed gradient occur along the river, which strongly control anabranching style through an influence on local sediment budgets. In relatively long (>10 km), lower gradient reaches (<0.0013) within the anabranching reach, sediment supply exceeds local transport capacity, bedrock usually only crops out in channel beds, and channels divide around alluvial islands which are formed by accretion in the lee of bedrock outcrop or at the junction with ephemeral tributaries. Riparian vegetation probably plays a key role in the survival and growth of these islands by increasing flow roughness, inducing deposition, and stabilising the sediments. Less commonly, channels may form by eroding into once-continuous island or floodplain surfaces. In shorter (<10 km), higher gradient reaches (>0.0013) within the anabranching reach, local transport capacity exceeds sediment supply, bedrock crops out extensively, and channels flow over an irregular bedrock pavement or divide around rocky islands. Channel incision into bedrock probably occurs mainly by abrasion, with the general absence of boulder bedforms suggesting that hydraulic plucking is relatively unimportant in this setting. Mixed bedrock-alluvial anabranching also occurs in a number of other rivers worldwide, and appears to be a stable and often long-lived river pattern adjusted to a number of factors commonly acting in combination: (1) jointed/fractured granitoid rock outcrop; (2) erosion-resistant banks and islands; (3) locally variable channel-bed gradients; (4) variable flow regimes.     

基于数值模拟的黄河下游不同情景溃堤洪水特性

The lower Yellow River still faces the threat of flood due to the unusual precipitation caused by global environmental change, river channel sedimentation, hidden danger in the dike and unfavorable river regime of ＂hanging river＂. According to the characteristics of the dike-break flood of the Yellow River, this paper has simulated, in six different scenarios, the dike-break flood routing by inputting the terrain data, typical historical flood data and land use data of study area to two-dimensional unsteady flow model. The results show that： firstly, the routing process of flood will occupy other rivers on the way and return to the rivers after reaching the lower reaches; secondly, in the same river reach, flood inundating area of north band is bigger than that at corresponding location of south bank under the same historical flood; thirdly, it is different in the degree of flood inundation in different regions due to different geographical locations in flood plain; fourthly, the area of mainstream where flood is deep and flow velocity is quick is relatively smaller, but the area of non-mainstream, where flood is shallow and flow velocity is slow, is relatively big; and finally, the possible influenced area of the dike-break flood is 141,948 km^2.     

Testing links between river patterns and in-channel characteristics using MRPP and ANOVA

This study tests the assumption that the characteristics of channels within multiple channel rivers are different from those of single channel rivers. Some river restoration approaches propose radical transformation of river patterns, from multiple to single channels, based on the link between river patterns and their in-channel characteristics. Determining the links between river patterns and their in-channel characteristics is complicated by differences in geology, history, climate and discharge among rivers. Furthermore, multiple channel rivers are composed of a mosaic of channel types with a range of in-channel characteristics. This study minimizes these problems by analysing a single river containing neighbouring single and multiple channel patterns with little change in discharge downstream, and by analysing all channel types. The study addressed two objectives: to determine the hydraulic geometry, energy, and sediment mobility characteristics of neighbouring single and multiple channel river patterns, and to test for statistical differences in these characteristics between patterns. The Renous River shows a wandering pattern for 11.5 km, with multiple channels around semipermanent islands and abandoned channels in the flood plain. The river displays a single channel river pattern where channels are confined by their valley walls, upstream and downstream of wandering. The analysis was conducted at three scales. First, the confined single channel and wandering multiple channel patterns were compared (pattern scale). Second, the confined channel pattern was compared to single and multiple channel sections within the wandering pattern (section scale). Third, all channel types were compared (channel type scale). Multi response permutation procedure (MRPP) and analysis of variance (ANOVA) were used to analyze differences between channels. Difference tests found no simple discrimination between the single and multiple channel river patterns of the Renous River. Tests between the single confined and multiple wandering channel patterns found few differences in the in-channel variables. The tests did find differences between multiple channel sections within the wandering pattern and confined single channels; however, a greater number of differences were found between multiple channel and single channel sections within the wandering pattern, highlighting the variability within the wandering pattern. Two groups emerged when all channel types were tested for differences: perennial main-channels containing the thalweg, and ephemeral side-channels. Therefore, side-channels define the in-channel characteristics of wandering rivers because few differences were found among main-channels in either pattern. This analysis suggests that all channel types, not just main-channels, should be investigated to obtain a complete picture of a river pattern prior to any restoration efforts. Engineers must exercise caution when applying the link between river patterns and in-channel characteristics to river restoration efforts.     

新疆主要河流水文极值变化趋势

水文极值是工程水文计算的基础资料,实测样本资料的变化直接影响水文设计值。基于1956-2006年的实测洪峰、洪量、年最小流量、最枯月径流量等资料,分析了各水文要素的变化及其趋势。结果表明:20世纪80年代中期以来超标准洪峰、洪量的频次增加,大多数河流洪水峰、量都呈增大变化趋势,说明新疆洪水又进入活跃期,在工程水文设计洪水计算中要应尽可能搜集和利用近期暴雨和洪水资料,在洪水系列中增加更多大洪水信息,提高设计洪水计算成果的稳定性。年最小流量和最枯月径流量是维持河流生命和河道两岸自然生态的基础流量,基流量增大有利于对生态补给、水利发电,水库蓄水,径流年内分配趋于均匀有利于水量年内调节。但在枯水径流分析计算中应充分重视不同年份最枯水量出现时间有明显推迟的迹象。     

Application of a new river classification scheme to Australia's tropical rivers

A revised typology of Australian tropical rivers was applied to the complete channel network (named and major rivers) shown on 1:250 000 topographic maps for three large drainage basins in northern Australia (Daly River, NT; Fitzroy River, WA; Flinders River, Qld). Reach mapping and classification were conducted using the revised typology. The 12 major river types proposed were: (1) bedrock rivers; (2) bedrock‐confined and ‐constrained rivers; (3) low sinuosity (straight) rivers; (4) meandering rivers; (5) wandering rivers; (6) anabranching rivers; (7) chains of ponds; (8) gullies; (9) floodouts; (10) lakes, swamps, billabongs and wetlands; (11) non‐channelized valley floors; and (12) estuarine rivers. The 12 major river types were developed based on river reach mapping for more than 264 000 km² of tropical Australian catchments. At scales larger than 1:250 000, subdivision of each major river type is recommended. In the Daly and Fitzroy catchments, confined and constrained rivers dominate, whereas in the Flinders and Fitzroy catchments, anabranching rivers dominate. The dominant river types need benchmarking with adequate numbers of control reaches so that channel changes induced by human and natural impacts can be measured by reference to the stability of these controls. Wandering rivers, floodouts and non‐channelized valley floors were rare for the 1:250 000 channel network in northern Australia but need inclusion in national parks.     

Is flooding in South Asia getting worse and more frequent?

South Asia is drained by some of the most flood‐prone rivers in the world. Flooding during the monsoon season is the most recurring, widespread and disastrous natural hazard in South Asia that results in enormous social, economic and environment consequences every year. Several massive floods have occurred in the recent decades causing huge economic losses and human suffering. On average, the total damage is close to USD 1 billion annually. To answer the question whether flooding in South Asia is getting worse and more frequent, all available data were considered: the annual peak discharge data for major rivers, post‐1985 information on floods from the global archive of large floods and palaeoflood records from nine Indian rivers. According to the global archive data, 372 large and 55 extreme flood events have occurred since 1985. Although there is no significant trend, all types of data point to clustering of large floods. Palaeoflood records show that modern floods (post‐1950) have higher flood levels than the late Holocene floods. Notwithstanding the limitations of data, there is enough evidence to conclude that (1) incidences of flood‐generating extreme rainfall event are rising and (2) human interventions have made the recent floods more destructive.     

Response and recovery of the Eel River, California, and its tributaries to floods in 1955, 1964, and 1997

Northwestern California is prone to regional, high magnitude winter rainstorms, which repeatedly produce catastrophic floods in the basins of the northern Coast Ranges. Major floods on the Eel River in 1955 and 1964 resulted in substantial geomorphic changes to the channel, adjacent terraces, and tributaries. This study evaluated the changes and the effects of a moderate flood in 1997 through field observations and examination of aerial photographs that spanned from 1954 to 1996. The purpose was to document the nature and magnitude of geomorphic responses to these three floods and assess the rates and controls on the recovery of the Eel River and its tributaries. Channel widening from extensive bank erosion was the dominant geomorphic change along the lower Eel River during major floods. As a result of the 1964 flood, the largest amount of widening was 195 m and represented an 80% change in channel width. Channel narrowing characterized the periods after the 1955 and 1964 floods. More than 30 years after the 1964 flood, however, the river had not returned to pre-flood width, which suggests that channel recovery required decades to complete. A long recovery time is unusual given that the Eel River is located in an area with a “superhumid” climate and has an exceptionally high sediment yield. This long recovery time may reflect highly seasonal precipitation and runoff, which are concentrated in 3–5 months each winter. In contrast to the main stem of the Eel River, the dominant effects of floods on the tributaries of the Eel River were rapid aggradation of channel bed and valley floor followed by immediate downcutting. Dendrogeomorphic data, aerial photographs, and field observations indicate that thick wedges of gravel, derived largely from hillslope failures in upper reaches of the tributaries, are deposited at and immediately upstream of the mouths of tributaries as the stage of the Eel River exceeded that of the tributaries during major floods. In the waning stages of the flood, the tributaries cut through the gravel at a rate equal to the lowering of the Eel and generated unpaired terraces and nickpoints. The complete process of deposition and incision can occur within a few days of peak discharge. Although reworking of some sediment on the valley floor may continue for years after large floods, channel morphology in the tributaries appears to be a product of infrequent, high magnitude events. The morphology of the tributary channel also appears to be greatly influenced by the frequency and magnitude of mass wasting in headwater areas of small basins.     

长江河源地区河流水文特性分析

本文简要介绍了青藏高原长江河源地区冰川,冻土和地质构造对水系发育和河况的影响,初步分析了该地区河流的经流、洪水、枯水、水温和冰情的变化规律.文中着重阐明河流洪水形成的基本特征,并据观测资料和洪水调查资料,探讨了百年一遇洪峰流量的分布规律,该成果可供长江河源地区铁路,公路桥涵设计参照使用.     

网状河流研究进展述评

网状河流作为一种新的冲积河流类型已经引起地貌学家、水利学家和沉积学家的关注 ,成为河流地貌领域、河流沉积领域以及河流水动力领域的研究热点之一。本文在介绍网状河流基本概念的基础上 ,综合国内外的研究成果 ,从河流的平面形态、边界条件、沉积特征、水动力条件以及在河型演化序列中的位置等方面 ,对网状河流的研究进展作一较全面的述评 ,并指出目前研究的薄弱环节 ,以利于研究者把握网状河流的研究现状 ,并推动对网状河流的进一步探讨。     

Natural diversion of the ramu river in Papua New Guinea

At present, the Ramu River in Papua New Guinea flows directly into the Bismarck Sea, while the adjacent Keram flows into the Sepik River. There is evidence to suggest that the Ramu previously occupied the existing Keram water course, and has been gradually diverting its discharge into its present channel, probably over the last 4,000 years. The diversion process is not complete yet, and during the wet season flood water still travels across these two rivers. The most direct evidence to support this proposal of river diversion is that there are much larger meander bends on which the existing Keram stream channel is superimposed. The diversion of the Ramu is believed to be a result of relative sea‐level rise in the late Quaternary which altered the gradients of the Keram and Ramu rivers, and may have been facilitated through neo‐tectonic movement of the floodplain.     

天山北坡“96.7”洪水致灾原因分析

１９９６年７月中，下旬，天山北坡发生了特大洪水，其洪峰之高，洪量之大为历史上所罕见，形成了建国以来新疆从未有过的特大洪灾，本文综合实地考察结果，在对洪水特点分析基础上，结合对本次洪水致灾过程的研究，详尽分析了天山北坡“９６．７”洪水致灾原因。