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1.
作为中国现代河流地貌研究的开拓者和奠基人,沈玉昌先生对开创流水地貌实验研究的初衷,为后人创新流水地貌实验开拓了先河,特撰写本文纪念先生100周年诞辰。主要内容有：①憧憬河流地貌实验与筹建流水地貌实验室。包括先生的初衷、实验室调研与筹建、实验试运行及起步实验;②流水地貌实验室扩建及实验研究蓬勃发展。包括结合国家重大及地方委托项目开展的一系列实验研究,开拓流域地貌系统及坡面发育演变的实验,建立河流地貌过程响应实验相似型理论;③河流地貌实验的新进展。包括河流地貌实验室建设及实验装置更新,河型系统发育演变过程实验的新进展,穹隆与坳陷非均匀升降对河流地貌系统发育影响的实验等。最后进行了展望,为了使中国实验流水地貌学研究继续深化,需要进行6个方面创新探索,特别是：加强构造运动、气候变化及人类活动快速变化导致的非稳定状态河流动力地貌过程实验研究,揭示其复杂性、敏感性及前兆性特征,加强实验研究力量的协作与融合,加强流水地貌实验研究的综合性、交叉性学术交流。 相似文献
2.
《Basin Research》2018,30(1):20-34
Relay ramps are integral components of normal fault systems that control sediment transport pathways in evolving rifts. We attribute differences in the geometry of fluvial systems that drain relay ramps to the scale of the ramp bounding fault segments, the spacing between segments and the amount of overlap between segments. Previous conceptual models for relay ramp geomorphological evolution have assumed that ramp fluvial catchments develop on the ramp surfaces and flow parallel to fault strike into the adjacent basin. Numerous examples exist in nature, however, that show that this is not ubiquitous. The fundamental question of what drives differences in fluvial geometry in these settings has, to date, not been fully addressed. We selected 27 relay ramps across the Basin and Range, western North America, and mapped, via GPS and remote sensing, the faults and ramp fluvial systems associated with each site. The sites represent a range of fault scales, which we define by the total outboard fault length, and a range of spacing and overlap values in order to better understand the structural controls on differences among ramp fluvial systems. Results show that the majority of a relay ramp surface drains parallel to fault strike when the outboard fault is less than about 15 km long. High overlap/spacing ratios are associated with relays along shorter (<15 km long) outboard faults, whereas lower overlap/spacing ratios are associated with relays along longer faults. Relays with lower overlap/spacing values may be more common along longer outboard faults because they survive for longer periods of time in the landscape. Our geomorphological observations can be used to predict synrift depocenter locations along segmented faults, but these observations only apply if the faults are short (<15 km long) and in early rifting stages. At longer fault lengths, ramp fluvial system geometry has no discernable relationship with any specific structural parameter. 相似文献
3.
国外干旱区河流地貌研究综述 总被引：2，自引：2，他引：2
国外学者对干旱河流地貌的研究可划分为:干旱河流地貌研究的初级阶段、发展阶段、模拟阶段和微观理论深入阶段。近半世纪以来,国外干旱河流地貌研究的主要进展有:研究领域的扩大,向模拟试验和定位研究方向发展,与水利工程、综合开发以及其它生产建设密切结合。 相似文献
4.
Global warming and fluvial geomorphology 总被引：5，自引：3，他引：5
Future global warming has a number of implications for fluvial geomorphology because of changes in such phenomena as rates of evapotranspiration, precipitation characteristics, plant distributions, plant stomatal closure, sea levels, glacier and permafrost melting, and human responses. Potential changes in rivers are outlined in this review in the context of changes in the intensity of rainfall, the activity of tropical cyclones, runoff response (including that of Europe, dry lands and high latitude environments), and geomorphological reactions, including rates of soil erosion. In general, however, much work remains to be done to establish the full range of geomorphological responses that may take place in fluvial systems. 相似文献
5.
沈玉昌与中国现代地貌学 总被引：3，自引：0，他引：3
沈玉昌教授是我国着名的地理学家和杰出的地貌学家。在60年的地理科学工作中,他对我国现代地貌学发展做出了卓越的贡献。从河流地貌、地貌区划与地貌制图、应用地貌等方面进行了综述。 相似文献
6.
7.
Merged remotely sensed data for geomorphological investigations in deserts: examples from central Saudi Arabia 总被引：1，自引：0，他引：1
Image merging has gained acceptance in geological remote sensing, however it has rarely been applied in geomorphology. We report on the usefulness of principal components substitution (PCS) to merge IRS panchromatic data with multispectral Thematic Mapper (TM) imagery, to map commonly encountered desert geomorphological features, and in relative age dating of alluvial surfaces. The merged data were applied to the identification and mapping of geomorphological features along two geolo-gically different mountain fronts in central Saudi Arabia. Two types of geomorphological maps have been created. A morphogenetic map that distinguishes between aeolian landforms, fluvial landforms, desert pavements, and gypsum crusts. Second, a morphochronological map, which shows the relative age of four geomorphic surfaces developed on an alluvial fan. The construction of the two maps is supported by field observations and laboratory measurements. Using the optimum index factor (OIF), a TM band 1, 5 and 7 image (of 20 merged composites) was found to be the optimum colour composite image for the geomorphological features in this arid environment. We discuss our findings in the context of the spatial and spectral properties required for applied geomorphological remote sensing. 相似文献
8.
实验流水地貌学研究的回顾与展望 总被引：4，自引：0，他引：4
本文简述了地貌实验研究的概况,罗列了我国主要的地貌实验室、站,叙述了我国30多年来,河型造床试验、边界条件及构造运动对河型发育影响实验,应用河流地貌实验、试验理论和技术方面的进展情况,指出实验研究中存在的问题,在回顾基础上,展望了流水地貌实验研究的未来发展趋势。 相似文献
9.
An analysis is made of the manifestations of fluvial and aeolian processes in the southern, developed areas of Irkutsk oblast belonging to the upstream part of the Angara basin. We examine the formation probability and the recurrence frequency of disastrous geomorphological events. The study revealed their association with positive (fluvial processes) and negative (aeolian processes) extremes and anomalies of atmospheric moistening. It is shown that at the time of an extreme event the rate of the processes and the volumes of transported material increase abruptly (by an order of magnitude), and the affected areas show an increase. The criteria for an extreme fluvial event can be represented by a spasmodic buildup of gullies and appearance of new gullies, an abrupt increase in soil losses due to erosion of agricultural lands reaching 100?200 m3/ha, death of crops, releases of mud flows, and destruction of roads, dams, bridges and other structures. The geomorphological consequences of the 1960 summer storm rains are considered to exemplify the disastrous fluvial events. The extremes of aeolian processes have the character of hurricanes encompassing most of the agricultural areas of Irkutsk oblast. The hurricanes are accompanied by a powerful removal of aeolian material from north-west to south-east to the water area of Baikal, to windward slopes and watershed divides of the mountain ranges along the eastern coast. The finest dust particles are transported to neighboring areas of Buryatia, Mongolia and China. The negative consequences of extreme aeolian events include agricultural crop destruction or damage, soil deflation, pollution of surface waters by deflation products, fires, damage to power transmission lines or even death of people. The findings were used in zoning the Upper Angara region according to the degree of geomorphological security of the territory. 相似文献
10.
R.C. Chiverrell G.C. Foster P. Marshall A.M. Harvey G.S.P. Thomas 《Geomorphology》2009,109(3-4):222-235
Variations in the coupling of sediment transfer between different parts of a fluvial catchment, e.g., hillslope to axial stream, can hamper understanding but are an integral part of the geomorphological record. Depositional environments respond to a combination of land use, climate, storms (floods), and autogenic conditioning. The distribution of sediment in the upland landscapes of NW England is out of equilibrium with contemporary climate and geomorphological processes; more a function of peri- and paraglacial mobilisation of glacigenic deposits. Soil and vegetation development after deglaciation have interrupted any progression toward sediment exhaustion with sediment release controlled largely by extrinsic perturbation, with late Holocene anthropogenic activity, climate and extreme hydrological events the likely candidates. This paper presents a new radiocarbon-dated Holocene geomorphological succession for the River Hodder (NW England), alongside evaluating new palaeoecological and geoarchaeological data to discern the impacts of human activity. These data show a late Holocene expansion in human occupation and use of the landscape since the Iron Age (700–0 cal. B.C.), with more substantial changes in the character and intensity of upland land use in the last 1300 years. The geomorphological responses in the uplands were the onset of considerable and widespread hillslope erosion (gullying) and associated alluvial fan development. Interpretation of the regional radiocarbon chronology limits gullying to four, more extensive and aggressive phases after 500 cal. B.C. The downstream alluvial system has responded with considerable valley floor deposition and lateral channel migration that augmented sediment supply by remobilising the existing floodplain terraces and led to the aggradation of a series of inset alluvial terraces. The timing of these changes between states of aggradation and incision in alluvial reaches reflects the increased connectivity between the hillslope and alluvial systems. Aspects of both the regional climate and land use histories are conducive to increasing discharge and sediment flux, but the region wide lowering of erosion thresholds appears a key driver conditioning these sediment-rich conditions and producing a landscape that was more susceptible to erosion under lower magnitude flows. 相似文献
11.
《Geomorphology》2005,64(1-2):1-23
Erosion and deposition processes lie at the centre of geomorphological explanation, but progress in understanding has been limited by a lack of appropriate high-resolution monitoring methodologies which permit detection of erosion and deposition dynamics. This paper presents a case for monitoring erosion and deposition at high temporal resolutions, and uses hypothetical approaches supported by example erosion and deposition events and analyses drawn from estuarine and fluvial systems. The paper first presents testable hypotheses to demonstrate the complexity of possible event combinations, sequences and juxtapositions for the erosion driving forces which underpin the need for high-resolution monitoring. Second, it summarises recent improvements to the Photo-Electronic Erosion Pin (PEEP) automatic erosion and deposition monitoring system, including the novel concept of Thermal Consonance Timing (TCT), which is particularly promising because it helps to define the timing of nocturnal events and through the entire hydrograph. Third, example results are discussed from high-resolution monitoring of bank erosion at a tidal site at Burringham on the River Trent in northern England. Tidal banks are revealed to be much more dynamic than previous conventional monitoring has indicated. A key result is that, because the high-resolution approach allows erosional and depositional activity to be assigned to specific periods of tidal inundation, it becomes possible for the first time routinely to produce ‘event-based’ erosion (36 mm h−1) and deposition rates (4.5 and 8.4 mm h−1). Such rate determinations are potentially very useful in the field validation of sedimentological and geomorphological models, including grain settling and resuspension theory. Fourth, through a longer term of aggregated daily data, a striking 2-week cycle of deposition and erosion emerges which correlates most strongly with spring-neap tidal cycling, but is moderated by wind stress effects. Sediment was deposited on the bank relatively quickly, over 4–5 days, but then removed by erosion rather slowly, over 9–10 days. Fifth, the dangers of low-resolution monitoring are illustrated by comparing the daily PEEP data set with a series resampled at a lower (14-day) frequency, to simulate the information generated by conventional resurvey methodologies. The low-frequency series failed adequately to represent the cyclicity, mean, range, variability and trend of bank elevation changes, and without this dynamics information, rate and process definition is very difficult, largely because of self-concealing activity. Sixth, a useful advance is illustrated by the fluvial erosion sequence for the River Wharfe (N. England). This shows how TCT can generate rare and important results with the definition of the precise time of an erosion event within the hydrograph: bank retreat here occurred very quickly, after initial inundation, and within 4 h of the flow peak-information which can be used to define thresholds for entrainment (e.g. critical shear stresses). Such high-resolution monitoring helps to unravel some of the erosional effects of complex sequences, combinations and juxtapositions of similar or different forcing events. Finally, high-resolution approaches have been adopted worldwide for fluvial, estuarine, mudflat and canal systems, but considerable potential exists for their development and use in these and other contexts (e.g. gully, hillslope, beach and dune environments), to improve understanding and modelling of geomorphological processes more widely. 相似文献
12.
《自然地理学》2013,34(5):453-478
This paper presents results of the geomorphological study of river elements for a morphostructural characterization of Hispaniola. The fluvial system and its primary and secondary drainage divides were delimited using a specially developed methodology. More than 120 fluvial basins were studied. The largest rivers are the sixth-order Yaque del Norte and Yaque del Sur. The fluvial density is in the range of 0.08-4.0 km/km2, with highest values in the Cordillera Central. There are two large hydrological regions, the Western and the Eastern, with a northeastern transverse diagonal boundary, coinciding with the direction of the Beata Escarpment. Using quantitative data to characterize the morphostructure of the fluvial network in Hispaniola enabled us to make comparisons with a Cuban network. As is shown, the river pattern in Hispaniola is basically tectonic, with a remarkable directional diversity in the main first-order drainage divide. In the Caribbean area, Eastern Cuba is the only other location with this pattern. 相似文献
13.
Lindsey J. McEwen & John A. Matthews 《Geografiska Annaler: Series A, Physical Geography》1998,80(1):17-36
A geomorphological and sedimentological case study is made of the Sprongdøla, a medium-sized river flowing in a predominantly bedrock channel in the mountains of southern Norway. Particular attention is given to bed material characteristics and potential sediment sources. Downstream patterns in clast size and shape, including sphericity and roundness, are poorly developed in the Sprongdøla. There is an apparent absence of down-stream fining and a large proportion of bedload in the lower channel remains in very angular and angular roundness categories. Covariance analysis of clast shape and roundness allows this to be attributed to the widespread input of coarse, angular rock particles derived from snow-avalanche activity on the valley sides and especially from frost-shattering of bedrock in the channel, which produces characteristically slabby clasts. The latter process is important in channel widening and in steepening the channel walls. Strictly fluvial processes, avalanche activity and frost-shattering are controlled in different ways by related annual environmental cycles. Their interaction in the context of the periglacial river channel produces a unique process-sediment-landform association that distinguishes alpine periglacio-fluvial systems from those associated with glacio-fluvial rivers and fluvial landscapes in the temperate zone. 相似文献
14.
We used a combined approach of a two-dimensional erosion and hillslope sediment delivery model (WATEM/SEDEM) and detailed geomorphological reconstructions to quantify the different components in a sediment budget for the Geul River catchment (southern Netherlands) since the High Middle Ages. Hillslope erosion and colluvium deposition were calculated using the model, while floodplain storage was estimated using field data. Our results show that more than 80% of the total sediment production in the catchment has been stored as colluvium (mostly generated by hillslope erosion), while almost 13% is stored in the floodplain since the High Middle Ages (this situation resembles a capacity-limited system). Model results for the period prior to the High Middle Ages (with a nearly completely forested catchment) show that far less sediment was generated and that most of the sediments were directly transported to the main river valleys or out of the catchment (a supply-limited system). Geomorphological analysis of a large alluvial fan shows the sensitivity of the study area to changes in the percentage of arable land.Our combined field data-modeling study presents an elegant method to calculate a catchment sediment budget for a longer period and is able to identify and quantify the most important sediment storage elements. Furthermore, it provides a valuable tool to calculate a sediment budget while only limited dated fluvial sediment sequences are available. 相似文献
15.
The fluvial environment of the central Po Plain, the largest plain in Italy, is discussed in this paper. Bounded by the mountain chains of the Alps and the Apennines, this plain is a link between the Mediterranean environment and the cultural and continental influences of both western and eastern Europe. In the past decades, economic development has been responsible for many changes in the fluvial environment of the area.This paper discusses the changes in fluvial dynamics that started from Late Pleistocene and Early Holocene due to distinct climatic changes. The discussion is based on geomorphological, pedological, and archaeological evidences and radiocarbon dating.In the northern foothills, Late Pleistocene palaeochannels indicate several cases of underfit streams among the northern tributaries of the River Po. On the other hand, on the southern side of the Po Plain, no geomorphological evidence of similar discharge reduction has been found. Here, stratigraphic sections, together with archaeological remains buried under the fluvial deposits, show a reduction in the size of fluvial sediments after the 10th millennium BC. During the Holocene, fluvial sedimentation became finer, and was characterised by minor fluctuations in the rate of deposition, probably related to short and less intense climatic fluctuations.Given the high rate of population growth and the development of human activities since the Neolithic Age, human influence on fluvial dynamics, especially since the Roman Age, prevailed over other factors (i.e., climate, tectonics, vegetation, etc.). During the Holocene, the most important changes in the Po Plain were not modifications in water discharge but in sediment. From the 1st to 3rd Century AD, land grants to war veterans caused almost complete deforestation, generalised soil erosion, and maximum progradation of the River Po delta. At present, land abandonment in the mountainous region has led to reafforestation. Artificial channel control in the mountain sector of the basins and in-channel gravel extraction (now illegal but very intense in the 1960s and 1970s) are causing erosion along the rivers and along large sectors of the Adriatic coast. These changes are comparable with those occurring in basins of other Mediterranean rivers. 相似文献
16.
Michael F. Thomas 《Singapore journal of tropical geography》2006,27(2):111-127
Historically, geomorphologists have applied uniformitarian principles based on a temperate normality to all water-worn landscapes. Isolation of tropical landforms within formal morphogenetic regions, which arose during the early history of the subject, has persisted. However, in a global geomorphology, plate tectonic motion, Milankovich cycles of climate change and invasive weather systems all render fixed climatic boundaries meaningless and, on every timescale of enquiry, interaction of the tropics with extra-tropical regions is fundamental. In tropical regions, the continuity of weathering processes through geologic time emphasizes their contemporary relevance and, with knowledge of Quaternary climate changes, increases understanding of the nature of landscape sensitivity and instability and fluvial sedimentation on millennial timescales. Examples are illustrated from northeast Queensland, Australia and northwest Kalimantan, Indonesia. Global concerns centred on hazards and resources need to be addressed through a reciprocal exchange of ideas involving greater focus on tropical areas. 相似文献
17.
Channel incision is part of denudation, drainage-network development, and landscape evolution. Rejuvenation of fluvial networks by channel incision often leads to further network development and an increase in drainage density as gullies migrate into previously non-incised surfaces. Large, anthropogenic disturbances, similar to large or catastrophic “natural” events, greatly compress time scales for incision and related processes by creating enormous imbalances between upstream sediment delivery and available transporting power. Field examples of channel responses to antrhopogenic and “natural” disturbances are presented for fluvial systems in the mid continent and Pacific Northwest, USA, and central Italy. Responses to different types of disturbances are shown to result in similar spatial and temporal trends of incision for vastly different fluvial systems. Similar disturbances are shown to result in varying relative magnitudes of vertical and lateral (widening) processes, and different channel morphologies as a function of the type of boundary sediments comprising the bed and banks. This apparent contradiction is explained through an analysis of temporal adjustments to flow energy, shear stress, and stream power with time. Numerical simulations of sand-bed channels of varying bank resistance and disturbed by reducing the upstream sediment supply by half, show identical adjustments in flow energy and the rate of energy dissipation. The processes that dominate adjustment and the ultimate stable geometries, however, are vastly different, depending on the cohesion of the channel banks and the supply of hydraulically-controlled sediment (sand) provided by bank erosion.The non-linear asymptotic nature of fluvial adjustment to incision caused by channelization or other causes is borne out in similar temporal trends of sediment loads from disturbed systems. The sediments emanating from incised channels can represent a large proportion of the total sediment yield from a landscape, with erosion from the channel banks generally the dominant source. Disturbances that effect available force, stream power or flow energy, or change erosional resistance such that an excess of flow energy occurs can result in incision. Channel incision, therefore, can be considered a quintessential feature of dis-equilibrated fluvial systems. 相似文献
18.
We examine the question of determining the place of geomorphology in the system of Earth sciences. The study revealed that, in spite of the differences in understanding the subject matter of science, there are at least seven integrating and generally accepted techniques of geomorphological investigations themselves: orographic analysis, cartometry, remote analysis of hidden landforms, morphometry, geomorphological mapping, modeling of geomorphological systems and conceptual development of the methodology. Emphasis is placed on the important role of geomorphological mapping in understanding all processes on land cover and the history of its development, assessing the natural resources and natural hazards, and in forecasting the evolution of the landscape. The technique of representing results from geomorphological investigations as a geomorphological map requires developing a classification of topographic features and landforms, and publications of A. N. Lastochkin and his followers are specifically focused on this issue. The integrating role of N. A. Florensov’s ideas of concepts concerning the continental orogenesis and geomorphological formations is pointed out. The autonomy of geomorphology in the system of Earth sciences is demonstrated but it is emphasized that it is not possible to further develop geomorphological knowledge outside the province of related Earth sciences, primarily geology and physical geography. A substantiation is given to the exclusiveness of the object of study (topography of land cover) and the subject (main topographic properties: morphology, genesis, age, and morphogenesis processes) which can be analyzed solely by geomorphological research techniques and development models. 相似文献
19.
Tufas are constructional landforms composed of calcium carbonate. They are common in karst terrains, and are known worldwide as useful archives of palaeoenvironmental information. In the case of fluvial tufas, these carbonate deposits experience net aggradation when environmental conditions are stable, whilst incision through the deposits occurs when conditions become wetter. In this study, the first of its type in temperate Australia, we used geomorphological and sedimentological evidence preserved in fossil tufas and alluvial terraces to investigate the fluvial history of Davys Creek (NSW, Australia). The nature and timing of fluvial changes along two quasi-independent reaches of the creek were synchronous, suggesting the operation of externally driven processes rather than local internal fluvial adjustments. Following a period of sustained aggradation, rapid incision occurred along the creek between 1500 and 1600 years before present ( bp ) in response to a shift to a moister climate. This was succeeded by a second major aggradation event (1500 years bp to 150 years bp ), then subsequent incision following the arrival of Europeans at 150 years bp. 相似文献
20.
Sediment-rich estuaries typically exhibit considerable dynamicity, with channel shifts and shoreline erosion/deposition occurring over timescales of years to decades. Contemporary behaviour is usually attributed to the immediate effect of short-term events (such as storms), longer-term forcing (such as sea-level change) or anthropogenic modifications to system controls (such as wave–tidal–fluvial regime and sediment supply). In this context, geological control is understood to provide an inherited framework within which an estuary will evolve. This paper examines the morphodynamics of two sand-filled, but sediment-limited, mixed-energy estuaries of Loughros Bay in northwest Ireland. Analysis of ebb channel morphometry shows that estuaries can be divided into upper and lower estuary components, which appear to represent a down-valley increasing energy gradient. Examination of historical ebb channel migration reveals three morphodynamic zones delimited by a significant spatial variability in channel mobility that reflects the distribution of specific structural controls along the estuary and their influence on the changing energy gradient. Based upon analysis of low tide channel migration over the last 172 years, three phases of geomorphic response are identified. In Loughros More, the behaviour is characterised by a 19th century phase of steady-state equilibrium; a subsequent period of dynamic response to extrinsic (storm) forcing; and, most recently, adjustment to intrinsically forced changes in structural control. In Loughros Beg, the phases are comparable, but contrast specifically in inlet and ebb-tidal behaviour. This analysis illustrates discontinuities in decadal- to century-scale forcing and morphological response, identified here as complex response. It suggests that the sedimentary evolution of coastal systems that have no appreciable external sediment supply is potentially more strongly determined by local variability in system character than climate or sea-level driven mechanisms. 相似文献