River Channel Evolution Research Articles

Avulsions in a Simulated Large Lowland Braided River

The understanding of the complicated braiding mechanisms in braided rivers is closely related to avulsions. They control the channel generation, migration and disappearance in large lowland braided rivers, and are considered to be the key factor that keeps the river maintaining a dynamic braided pattern. However, their occurring processes and mechanisms are still not well understood due to the lack of detailed measurements with sufficient temporal and spatial data covering multiple bifurcations. In the present study, a numerical model based on the physical process of hydrodynamics and sediment transport is used to simulate the suspended sediment transport and river channel evolution in braided rivers. The model predicted braiding processes are comparable to those observed in nature. Efforts are made to investigate the morphological processes that are key for river braiding. Three types of avulsions observed in natural rivers have been identified in the model predicted river and their evolution processes and controlling factors are examined based on the predicted flow velocity, sediment concentration, bed elevation and sediment size distribution. It was found that, a curving channel bend is the key factor in introducing a constriction avulsion, while the choking avulsion and apex avulsion are controlled by the water surface slope and bed elevation. They are mostly affected by the upstream channel pattern changes.

Research and Application Effect of High Precision Contemporanenous Display of River Channel and Sand Body Technology Based on Algorithm Optimization

The contemporaneous presentation of river channel, sand body and mud on the seismic attribution slice is the research that seismogeology personnel desire to realize. Especially at the oil field development stage, the research is very important to deploy the location of injection and production well. This paper takes A oil field, Bohai Bay area as the target region, on the basis of negative 90 degree rotation data volume, selects out the best Algorithm to depict river channel and sand body precisely and realizes the river and sand attributes data fusion. Based on this, the relationship between river, sand and mud were contemporaneously presented. Through combined research on well data, it verifies that the profile and slice of seismic data are in accord with well data. Based on this technology, the development and evolution of river channel and the internal structure of point bar were studied, and the historical evolution process of meander river channel was recovered, which provides a strong basis for residual oil research and high production adjusting well deployment.

Erratum to: Recent channel changes of the Jiangsu reach of the Yangtze river: an investigation from multi-temporal digital elevation models

The Yangtze River is the longest river in China. This river has a drainage area of 1.8 × 10 km, flowing 6300 km from the glaciers in the Qinghai-Tibetan Plateau eastward to the East China Sea. Each year, the Yangtze River supplies approximately 9 × 10 m of fresh water and 4.7 × 10 t of sediments to its estuary and the East China Sea (Chai et al., 2006). In addition, the major channel of the Yangtze River is known as the BGolden River Channel^ because it is one of the largest river transportation lines in China. The channel in the middle and lower reaches of the Yangtze River is nevertheless strongly affected by sediment erosion and deposition (Yang et al., 2002, 2007; Liu et al., 2007; Xu and Milliman, 2009). Additionally, flood disasters appear to have occurred more frequently in the last century (Zong and Chen, 2000; Yin and Li, 2001; Zhang et al., 2006). The river channel evolution of the Yangtze River has significant impacts on flood discharge, shipping and the sustainable development of its drainage basin; the importance of these effects has given rise to the construction of a group of water conservation projects in the drainage basin during recent decades. To utilize and exploit the Yangtze River sustainably, it is crucial to understand the evolution of channel erosion and deposition, particularly in the middle and lower reaches, considering their dense populations and strong economic activities. As a typical large river, the evolution of the Yangtze River, such as persistent erosion and siltation, is recorded in the details of its channel morphology (Chen et al., 2001). The variation in water and solids in the main channel of the Yangtze River is an important focus for understanding the channel morphology of the river, which calls for a detailed analysis of the changes along the riverbed of the Yangtze River (Wang et al., 2009). The lower reach of the Yangtze River comprises alluvial plains where the main channel meanders into wide curves. This reach may also be influenced by the construction of the Three Gorges Dam, which potentially increased erosion and brought dynamic sedimentation-erosion changes to the lower reach of the Yangtze River (Dai et al., 2005). Additionally, sediment transport of the Yangtze River may have various consequences on the riverbed morphology and changes in the water level. The increase in bank sedimentation in the Yangtze Delta area is often associated with the decrease in transported river solids (Wang et al., 2009), while the existing sediments are possibly becoming the main erosion sources (Li et al., 2006). In addition, activities such as deforestation and overgrazing have caused significant degradation of the drainage basins of the Yangtze River, and this situation has been aggravated in recent decades Dudgeon (1992); Yan and Qian, 2004; Liu and Diamond, 2005; Long et al., 2006). This degradation often increases the suspended sediment load and subsequently comes with extensive flooding. Furthermore, the degradation may also affect land-water interactions and the * Ping Lu luping@tongji.edu.cn

Self‐adjustment in rivers: Evidence for least action as the primary control of alluvial‐channel form and process

AbstractLeast action principle (LAP) in rivers is demonstrated by maximum flow efficiency (MFE) and is the foundation of variational mechanics based on energy and work rather than Newtonian force and momentum. Empirical evidence shows it to be the primary control for the adjustment of alluvial channels. Because most rivers flow with imposed water and sediment loads down valley gradients they have largely inherited, they self‐regulate energy expenditure to match the work they are required to do to remain stable. Overpowered systems develop a variety of channel patterns to expend excess energy and remain stable. Australia offers an opportunity to study low‐energy rivers closely adjusted to very low continental gradients. The anabranching Marshall and single‐thread Plenty Rivers flow down nearly straight channels with average H numbers [ratio between excess bed shear and width/depth (W/D) ratio] close to the optimum of 0.3 for stationary equilibrium. Ridge‐form divisions of the original channel width create anabranches that radically alter W/D ratios relative to bed shear, the same being true for short‐wide islands on the large low‐gradient Yangtze River in China. In contrast, Mount Chambers Creek in Australia's tectonically more active Flinders Ranges is accreting an alluvial fan with unstable distributary channels exhibiting H numbers well below the optimum. LAP also explains profound biases in Earth's stratigraphic record. Because meandering is an energy‐shedding mechanism, sinuous rivers sequester relatively little sediment resulting in all sequences being just a few tens of metres thick. In contrast, low‐energy braided disequilibrium systems can sequester sediment piles over a kilometre in thickness and tens of kilometres wide. LAP provides a new paradigm for river research by identifying the attractor state controlling river channel evolution. It links advances in theoretical physics to fluvial geomorphology, stratigraphy and hydraulic engineering and opens opportunities for diverse investigations in Earth system science. Copyright © 2016 John Wiley & Sons, Ltd.

A philosophy of rivers: Equilibrium states, channel evolution, teleomatic change and least action principle

Until recently no universal agreement as to a philosophical or scientific methodological framework has been proposed to guide the study of fluvial geomorphology. An understanding of river form and process requires an understanding of the principles that govern the behaviour and evolution of alluvial rivers at the most fundamental level. To date, the investigations of such principles have followed four approaches: develop qualitative unifying theories that are usually untested; collect and examine data visually and statistically to define semi-quantitative relationships among variables; apply Newtonian theoretical and empirical mechanics in a reductionist manner; resolve the primary flow equations theoretically by assuming maximum or minimum outputs. Here we recommend not a fifth but an overarching philosophy to embrace all four: clarifying and formalising an understanding of the evolution of river channels and iterative directional changes in the context of least action principle (LAP), the theoretical basis of variational mechanics. LAP is exemplified in rivers in the form of maximum flow efficiency (MFE). A sophisticated understanding of evolution in its broadest sense is essential to understand how rivers adjust towards an optimum state rather than towards some other. Because rivers, as dynamic contemporary systems, flow in valleys that are commonly historical landforms and often tectonically determined, we propose that most of the world's alluvial rivers are over-powered for the work they must do. To remain stable they commonly evolve to expend surplus energy via a variety of dynamic equilibrium forms that will further adjust, where possible, to maximise their stability as much less common MFE forms in stationary equilibrium. This paper: 1. Shows that the theory of evolution is derived from, and applicable to, both the physical and biological sciences; 2. Focusses the development of theory in geomorphology on the development of equilibrium theory; 3. Proposes that river channels, like organisms, evolve teleomatically (progression towards an end-state by following natural laws) and iteratively (one stage forming the basis for the next) towards an optimal end-state; 4. Describes LAP as the methodological basis for understanding the self-adjustment alluvial channels towards MFE. 5. Acknowledges that whereas river channels that form within their unmodified alluvium evolve into optimal minimum-energy systems, exogenic variables, such as riparian or aquatic vegetation, can cause significant variations in resultant river-styles. We specifically attempt to address Luna Leopold's lament in 1994 that no clearly expressed philosophy explains the remarkable self-adjustment of alluvial channels.

Quantifying the combined effects of multiple extreme floods on river channel geometry and on flood hazards

Effects of flood-induced bed elevation and channel geometry changes on flood hazards are largely unexplored, especially in the case of multiple floods from the same site. This study quantified the evolution of river channel and floodplain geometry during a repeated series of hypothetical extreme floods using a 2D full hydro-morphodynamic model (LHMM). These experiments were designed to examine the consequences of channel geometry changes on channel conveyance capacity and subsequent flood dynamics. Our results revealed that extreme floods play an important role in adjusting a river channel to become more efficient for subsequent propagation of floods, and that in-channel scour and sediment re-distribution can greatly improve the conveyance capacity of a channel for subsequent floods. In our hypothetical sequence of floods the response of bed elevation was of net degradation, and sediment transport successively weakened even with floods of the same magnitude. Changes in river channel geometry led to significant impact on flood hydraulics and thereby flood hazards. We found that flood-induced in-channel erosion can disconnect the channel from its floodplain resulting in a reduction of floodwater storage. Thus, the frequency and extent of subsequent overbank flows and floodplain inundation decreased, which reduced downstream flood attenuation and increased downstream flood hazard. In combination and in summary, these results suggest that changes in channel capacity due to extreme floods may drive changes in flood hazard. The assumption of unchanging of river morphology during inundation modelling should therefore be open to question for flood risk management.

River bank erosion and channel evolution in sand-bed braided reach of River Chenab: role of floods during different flow regimes

Braided reaches of large rivers in alluvial plains show major morphological changes, particularly the external bank erosion, due to the flood events. This paper highlights the bank erosion and channel evolution induced by eleven different flood events in a 7-km long reach of the River Chenab, Pakistan. The impact of floods on river bank erosion and channel evolution is analyzed under low and high flow conditions. Flood-induced changes, for river’s external banks and channel evolution, were assessed by processing Landsat ETM+ images in ArcGIS tool, and their inter-relationship is evaluated through regression analysis. The results revealed that the major morphological changes were triggered by the flood events occurred during the high flow or Monsoon season (July–September), whereas the flood events of similar magnitude occurring during low flow season (October–March) did not induce such changes. Mostly, the erosion remained limited to the middle part of the reach, where the branch channel flows along the bank. The average annual bank erosion rates are much higher as compared with a global scale. Data analysis showed a strong correlation between the mean high flows and total bank erosion indicating that Monsoon seasonal flows and floods are responsible for bank erosion. The present study further identifies the river bank locations highly susceptible to erosion by developing the correlation between bank erosion and branch channel progression. Strong correlation for bank erosion could be established with the shift of branch channels position flowing along the banks in braided reaches of sand bed rivers. However, the presence of sand bars along the river banks resulted in reduced erosion that weakens this relationship. The findings of the present study can help develop better understanding about the bank erosion process and constitute a key element to inform and improve river bank management.

Strength and erosion mechanism of soft bedrock under high shear stresses

Bedrock erosion plays a critical role in mountain river channel evolution, especially, where there are hydro-projects with high velocity flow conditions. In this study, laboratory experiments are carried out to investigate strength and erosion mechanism of soft bedrock under high shear stresses by high velocity open channel flows. Prototype bedrock from the upper reaches of Yangtze River is employed as testing samples. New observed dataset is generated concerning the flow, bedrock strength and evolution of bedrock erosion, which can be exploited to evaluate bedrock erosion rate and test mathematical bedrock erosion models.

Analysis of channel evolution characteristics in the Hobq Desert reach of the Yellow River (1962–2000)

A series of problems, resulting from sediment deposition and channel silting, have occurred on the Hetao Plain as a result of changes to the Hobq Desert reach of the Yellow River. Therefore, improved research on channel evolution in this reach is vitally important. Using profile data from 80 channel cross-sections obtained in 1962, 1982, 1991 and 2000 from the Yellow River in the Hobq Desert, we showed that there was serious sediment deposition here (especially for the tributary section in the eastern desert) and that maximum sediment deposition occurred during 1982–1991. As sediment was deposited along the mobile channel, the channel trunk shrank and moved to the north. The characteristics of river channel evolution are dramatically different between the western and the eastern Hobq Desert reaches of the Yellow River, which include desert and the tributary sections, respectively. Erosion mainly occurred in the desert section, whereas sediment deposition occurred in the tributary section, with peak values at the mouths of on Yellow River tributaries. The desert section had a larger average erosion rate and smaller accumulation rate than the tributary section. The influences of tectonic movement and stream gradient on channel evolution in this fluvial reach were minimal. The sediment inputs from ten Yellow River tributaries (especially during flood seasons) have dominated channel evolution in these tributaries. The building of artificial levées has intensified sediment deposition in the channel, whereas the reduction of mainstream discharge (especially in the flood seasons), caused by the operation of reservoirs and water diversion activities (such as for agricultural irrigation), has further intensified the sediment deposition in the river channel.

A research of influence of neo-tectonic movement on alluvial rivers: Review and prospect

The study of neo-tectonic movement and its impact on alluvial river can deepen the understanding of the complex response theory in a geomorphic system and the complex hypothesis of multi- cycle deposition, and investigate thoroughly the relationship between sedimentary sequence and basin depositing processes, which can be widely applied to earth science, water engineering, traffic transportation, communications, oil and gas exploration and development, etc. In this paper, it is mainly reviewed the research progress of the influence of neo-tectonic movement in alluvial rivers, and neo-tectonic movement is described very briefly.In the embryonic period of the neo- tectonic movement, the study of the drainage pattern in a basin and the river towards controlled by the neo- tectonic movement, had been increasingly popular as a new discipline, but mainly focused on the geologic interpretation. Since the 1970 s,research on the neo-tectonic stress field can help us understand the neo-tectonic mechanism and dynamics. In author's point of view, active tectonics can be taken as part of the neo- tectonic movement, and the type and ratio of neo- tectonic movement has significant effect on alluvial river morphology and channel evolution, including the plane form, channel width, longitudinal profile, cross section, sinuosity, braided index, cutting strength and range, channel pattern,transport type and amount of sediment, which shows the complexity, hierarchy, sensitivity and prophetic. Influenced by active fold, uplift and depression on river longitudinal profile development, the compensation of subsidence by the sedimentation is concerned specially. As for the influence of neo- tectonic movement on alluvial river plane shape, the sinuosity was taken as the barometer of alluvial river in response to neo-tectonic activity. As for the effect of active fault on river development and evolution, sensitivity and prophetic are especially mentioned. This paper deals with the research progress in the bedrock exposed on riverbed by active uplifting, which resulted in developing both pressed and release meandering along upstream and downstream, respectively, and the so called "New structure", formed by river erosion. The traditional research methods and techniques are not generally described but mentioned that the experiment simulation has obtained remarkable achievements at home and abroad, and the mathematical simulation is just unfolding. It is prospected that at first, to pay attention to the crossing, permeating and comprehensive research of neo- tectonic movement impacting to alluvial river, the second to focus on effects of rapid tectonic movement to alluvial river, the third to observe regularly lifting rate of neo- tectonic movement, the riverbed evolution and sediment transportation in the neo-tectonic active area, the fourth, to take caution more with the physical model experiment and mathematic simulation, in which there is a great space for development, and finely to strengthen the cooperation and fusion of research ability.The study will enter a new stage of development.

Gravel-bed channel changes upstream of a reservoir: The case of the Dunajec River upstream of the Czorsztyn Reservoir, southern Poland

Despite a significant increase in the number of dam reservoirs in the world in the last century, the effects of these structures on the evolution of river channels above them are poorly understood. Constructed in 1997 in the Polish Carpathians, the Czorsztyn Reservoir (CR) has raised the base level of the single-thread, gravel-bed Dunajec River. An analysis of five sets of aerial photographs and orthophotos from the period before (1977, 1982, 1994) and after (2003, 2009) the construction of the CR allowed me to investigate the temporal and spatial impact of the raised base level of the river upstream of the reservoir on the evolution of the river channel. Comparison of channel width changes in the backwater river section with changes observed in the control section unaffected by the presence of the reservoir has shown that in the pre-dam period differences in the evolution of the river channel in the backwater section and in the control section were not statistically different. In the periods without major floods, both channel sections were dominated by channel narrowing or a relative stability of channel width. In the post-dam period, a major flood in 1997 caused more than two times greater channel widening in the backwater section than in the control section. The extent of channel widening in the longitudinal channel profile reached farther upstream of the reservoir than the extent of the backwater itself. In the later part of the post-dam period without major floods, channel narrowing were similar in the backwater section and the control section, as had been the case in the period before the reservoir construction. The comparison of changes in the width of the channel in the backwater and control sections indicates that channel widening in the backwater, interpreted as an early stage of backwater channel adjustment, was reinforced by the flood of 1997. This study shows that the use of a control section makes it possible to isolate reservoir effects from flood effects in the context of channel dynamics.

Constraining the stream power law: a novel approach combining a landscape evolution model and an inversion method

Abstract. In the past few decades, many studies have been dedicated to the understanding of the interactions between tectonics and erosion, in many instances through the use of numerical models of landscape evolution. Among the numerous parameterizations that have been developed to predict river channel evolution, the stream power law, which links erosion rate to drainage area and slope, remains the most widely used. Despite its simple formulation, its power lies in its capacity to reproduce many of the characteristic features of natural systems (the concavity of river profile, the propagation of knickpoints, etc.). However, the three main coefficients that are needed to relate erosion rate to slope and drainage area in the stream power law remain poorly constrained. In this study, we present a novel approach to constrain the stream power law coefficients under the detachment-limited mode by combining a highly efficient landscape evolution model, FastScape, which solves the stream power law under arbitrary geometries and boundary conditions and an inversion algorithm, the neighborhood algorithm. A misfit function is built by comparing topographic data of a reference landscape supposedly at steady state and the same landscape subject to both uplift and erosion over one time step. By applying the method to a synthetic landscape, we show that different landscape characteristics can be retrieved, such as the concavity of river profiles and the steepness index. When applied on a real catchment (in the Whataroa region of the South Island in New Zealand), this approach provides well-resolved constraints on the concavity of river profiles and the distribution of uplift as a function of distance to the Alpine Fault, the main active structure in the area.

CONCEPTUAL MODEL FOR ASSESSING THE CHANNEL CHANGES UPSTREAM FROM DAM RESERVOIR

Abstract Most of geomorphological studies related to the impact of dam reservoirs are focused on its effect on the river channels downstream of dams. However, little is known about the evolution of river channels upstream of dams (in backwater areas). In this paper I propose a conceptual model of alluvial channel changes in the backwater. It assumes that three conditions of a channel that may occur in the pre-dam period. These are sediment supply deficit, balance and surplus compared to the river transport capacity. These conditions can be strengthened, stable or weakened. In the post-dam period these conditions is modified by the influence of the dam reservoir, which may affect the trajectory of channel changes, as well as its response and adjustment time in the backwater. The adjustment of channel parameters, in spite of the reservoir operation mode, also depends on the local river, reach characteristics and the magnitude and frequency of floods. Therefore, the use of an appropriate reference reach is inherent in this model. The model suggests that some adverse changes to backwater channels degraded by the regulation can be hampered. The model is based on Lane’s balance concept. It may be useful for explaining and predicting channel changes upstream of reservoirs and forming hypotheses in other studies.

Tying bulk watershed properties to mountain river channel evolution

Rivers evolve over tens to thousands of years, winding and drifting and branching from single channels to braided, complex flows. Understanding exactly how and why rivers change course is a complex problem that depends on the erosion of the landscape and incorporates a range of variables, from local environmental conditions, such as the precipitation rate, to the topography, water chemistry, and properties of the rocks in the watershed. At smaller scales, channel evolution depends on the physical properties of, and interactions between, individual grains of sediment. Correlating across this entire range of scales is incredibly difficult, but using a set of comparable observations from 83 watersheds in the U.S. Rocky Mountains, Mueller and Pitlick tie climatic, topographic, and geologic features to sediment processes and river evolution.

Seamless Mapping of River Channels at High Resolution Using Mobile LiDAR and UAV-Photography

Accurate terrain models are a crucial component of studies of river channel evolution. In this paper we describe a new methodology for creating high-resolution seamless digital terrain models (DTM) of river channels and their floodplains. We combine mobile laser scanning and low-altitude unmanned aerial vehicle (UAV) photography-based methods for creating both a digital bathymetric model of the inundated river channel and a DTM of a point bar of a meandering sub-arctic river. We evaluate mobile laser scanning and UAV-based photogrammetry point clouds against terrestrial laser scanning and combine these data with an optical bathymetric model to create a seamless DTM of two different measurement periods. Using this multi-temporal seamless data, we calculate a DTM of difference that allows a change detection of the meander bend over a one-year period.

Study on the Evolution Mathematical Model for the Downstream Riverbed of Water Conservancy Hub Project

In water conservancy hub projects, an analysis of the downstream river channel evolution is a very important management reference. Through the construction of the mathematical model for riverbed evolution and also using all original parameters, the evolution trend of river channel can be simulated, providing an important reference for management and maintenance, and also proving the deduction of the mathematical model can keep consistent with the actual trend.

Changes in the sediment load of the Lancang-Mekong River over the period 1965–2003

Changes in the sediment load of a river can have important impacts on river channel evolution, nutrient fluxes, aquatic ecology and delta erosion and sedimentation, and the possibility of changes in the sediment load of the Lancang-Mekong River has attracted increasing concern in recent years. Existing studies present conflicting findings regarding the nature and magnitude of recent changes in the sediment load of the Lancang-Meking River and the authors have attempted to assemble the most reliable data on annual sediment loads for the period 1965–2003, to assess recent trends in the sediment load of the river. The changes in annual sediment load at 7 stations on the river are analyzed. Important sediment contributing areas are found in the reaches between Gajiu and Yunjinghong, Chiang Saen and Luang Prabang and downstream of Nong Khai. The sediment load increased at Gajiu, Yunjinghong and Chiang Saen over the period 1985–1992 because of serious soil erosion caused by the expansion of cultivation, the replacement of natural forest by plantations and land disturbance associated with hydropower dam construction. A marked reduction in sediment load occurred at Gajiu after the impoundment of the Manwan Hydropower dam on the Lancang River, but this reduction was not evident downstream at Yunjinghong and the stations further downstream. Significant increases in sediment load appeared at Mukdahan and Khong Chiam. These contrasting patterns of change reflect the influence of sediment contributions from the intervening catchment areas and channel systems as well as storage and remobilization of sediment from the channel system and the impact of hydraulic works such as irrigation systems. The long term mean annual sediment load of the Mekong River at its mouth is estimated to be ca. 145×106 t a−1, which is lower than previously reported values and it seems likely that this will be reduced in the foreseeable future.

New approach to understanding sediment transport

Sediment transport is an important factor in the evolution of river channels. Bed load sediment flux, defined as the volume of particles crossing a vertical surface per unit time per unit width, is a common way to describe sediment transport. However, quantifying bed load sediment flux in terms of conceptually simple quantities is challenging, as the motion of particles in turbulent water is very complex. In a set of four related papers, Furbish et al. developed a new probabilistic definition of bed load transport and verified their approach using laboratory experiments and model simulations. Their approach, which treats particle positions and motions as stochastic quantities, shows how the particle activity and velocity distributions are key elements in describing sediment flux. Their experiments, using high‐speed imaging of sand particle motions in a laboratory tank, allowed them to directly observe particle behavior and test their theory. Model simulations also verified their approach. (Journal of Geophysical Research‐Earth Surface, doi:10.1029/2012JF002352, 2012, doi:10.1029/2012JF002353, 2012, doi:10.1029/2012JF002355, 2012, and doi:10.1029/2012JF002356, 2012)

Study on Flood Control Demonstration of Huangshi Navigation Sign Maintenance Project of Wuhan Yangtze River Waterway Bureau

In the paper, the recent river channel evolution characteristics of the Huangshi river section, where the Huangshi Yangtze navigation sign maintenance project will be located, is analyzed. The effect on the water level and flow speed caused by the project is studied by using the river hydraulics calculating method. The river shore slope stability and dyke seepage are calculated. The effect on the river regime, flood discharge and flood control works is comprehensively discussed. Studying results show that the effect caused by the project on the river regime and flood control works etc. is very limited.

Visualization of River Channel Evolution of the South Branch in Yangtze Estuary Supported by GIS

Abstract Supported by GIS, several of charts of the South Branch of Yangtze estuary from 1900 to 2001 was digitized and Digital Elevation Model (DEM) of channel was established, based on which evolution of it since 1900 was visualization. The results show that: (1) DEM is an effective means for visualization and quantitative analysis of the channel evolution. (2) From 1900 to 2001, the channel storage volume in the south branch of Yangtze river slightly increased with an average annual increment of 2.7 million m3 at the depth of 0m; the entire river area was characterized by mild erosion, with the average annual erosion volume of 3.3 million m3 and average annual erosion thickness of 0.37 cm (including artificial dredging and reclamation as well as dredging amount). (3) The erosion and deposition state varied in different sections and at different time. Before 1958 and after 1979, the channel was characterized by erosion and expansion, while it was marked by deposition from 1958 to 1979; the erosion and deposition in the section of the entrance and exit of the channel in the south branch varied more violently than that in the middle section of the channel.