Fluvial Processes

The texture of the drainage system Is influenced by rock type and structure, the nature of the vegetation cover and the type of climate. The drainage density affords a measure of comparison between the development of one drainage system and another. It is calculated by dividing the total length of a stream by the area it drains, and is generally expressed in kilometres per square kilometre. 

Throughout its length, a river channel has to adjust to several factors that change independently of the channel itself. These include the different rock types and structures across which it flows. The tributaries and inflow of water from underground sources affect the long profile of a river. Other factors that bring about adjustment of a river channel are flow resistance, which is a function of particle size, and the shape of transistory deposits such as bars, the method of load transport and the channel pattern including meanders and islands. Lastly, the river channel must also adjust itself to the river slope, width, depth and velocity. 

Meanders, although not confined to, are characteristic of flood plains. The consolidated veneer of alluvium, spread over a flood plain, offers little resistance to continual meander development. Hence, the loops become more and more accentuated. As time proceeds, the swelling loops approach one another. During flood, the river may cut through the neck, separating two adjacent loops, thereby straightening its course. As it is much easier for the river to flow through this new course, the meander loop is silted off and abandoned as an oxbow lake (Fig. 3.16). 

A river is described as being braided if it splits into a number of separate channels or anabranches to adjust to a broad valley. The areas between the anabranches are occupied by islands built of gravel and sand. For the islands to remain stable, the river banks must be more erodible so that they give way rather than the islands. Braided channels occur on steeper slopes than do meanders. 

River terraces are also developed by rejuvenation. In the lower course of a river, uplift leads to the river cutting into its alluvial plain. The lateral and downstream migration of meanders means that a new flood plain is formed but very often paired alluvial terraces, representing the remnants of the former flood plain, are left at its sides (Fig. 3.17). 

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Polar and subtropical fronts have shifted southwards in the (geologically) recent past and many regions that are arid today once had a more humid climate. Conversely, many of the present humid regions were much drier in glacial periods, especially between 20,000 and 13,000 BP when aeolian processes influenced land formation more than at present. Mass wasting, fluvial processes and aeolian processes are the most important landform-shaping factors in arid and semi-arid regions. 

Fluvial processes in arid regions produce typical landforms. These are different in high-relief and low-relief areas. 

Surficial deposits at XY are dominated by tills and colluvium, which have been locally reworked by alluvial and glacio-fluvial processes (Figs. 1 2a). On the transect reported herein, the depth of overburden varies from negligible on mountain sides to at least 5 m thick in central parts of the till plain in central valley areas (unknown maximum thickness). In the section of the traverse the XY ore zone is c. 10 m thick, and occurs below c. 3 m of colluvial overburden (Fig. 2). Pedogenesis is generally restricted to minor to moderate horizonation that has produced predominantly brunisols (Canadian Soil Classification System, Agri-Canada 1998). 

It was once thought that the saltiness of the modem oceans simply represents the storage of salts derived from rock weathering and transported to the oceans by fluvial processes. With increasing knowledge of the age of the earth, however, it was soon realized that, at today s rate of delivery of salt to the ocean or even at much reduced rates, the total salt content and the mass of individual salts in the... 

Figure 1.2 Classic estuarine zonation depicted from the head region, where fluvial processes dominate, to the mid- and mouth regions where tidal and wave processes are the dominant controlling physical forces, respectively. Differences in the intensity and sources of physical forcing throughout the estuary also result in the formation of distinct sediment facies. (Modified from Dalrymple et al., 1992, with permission.)...

Panin A. V., Walling D. E., and Golosov V. N. (2001) The role of soil erosion and fluvial processes in the post-fallout redistribution of Chernobyl-derived caesium-137 a case study of the Lapki Catchment, central Russia. Geomorphology 40, 185-204. 

White, 1988 Ford and Williams, 1989 Gillieson 1996). The classifications are all generally similar although they differ somewhat in detail. The present paper focuses on a specific sub-set of cave sediments the clastic sediments derived from surface and subsurface weathering and carried into and through the cave system by mainly fluvial processes. 

The modem landforms of the sea bottom and coasts resulted from a joint action of arid erosion, marine, lacustrine, and fluvial processes, as well as tectonics. 

Changes in Fluvial Processes and Fluxes - Natural and Anthropogenic... 

As this cover forms coastal lowlands and river valleys as a consequence of fluvial processes, it occupies areas of urbanization and infra-structural development. Hence, due to it being the foci of economic activity, it is a very important area for constructional activities. Major subsurface problems arising from soft soils are also to be found in this map unit. 

The modification of the resistance law by introducing the bed roughness boundary layer brings less changes in flow calculation represented by depth and depth-averaged velocity but significant correction of shear velocity and subsequently sediment transport. The proposed modification will affect other aspects in fluvial processes, which will be clarified successively. 

Tsujimoto, T. 1999. Fluvial processes in streams with vegetation. Journal of Hydraulic Research 37(6) 789-803. 

When flow and fluvial process in a stream are discussed, vegetation is a key from the view point of rive ecosystem as well as flood management. Recently, 2D depth averaged analysis has become popular where vegetation is regarded as dispersive obstacles represented by form drag, and it is expected to apply to description of fluvial process in a stream with vegetation (Tsujimoto 1999). 

Recently numerical analysis on 2D depth-averaged flow and fluvial process has become familiar, the treatments of flow and sediment transport should be carefully prepared based on the above discussion. Discussion in this paper is limited to 2D behavior of flow and suspended sediment concentration in a straight channel with vegetation zone, further discussion should be developed in more general 2D analysis under more complicated conditions. 

In contrast, their multifunction of movement of both sample were decreased the propagation velocity of wave height and length of ripples. Then, POM behavior with ripples was modeled. The proposed model will affect other aspects in ecosystem management based on fluvial processes. 

Leopold, L.B., Maddock, Jr., T. (1954). The flood control controversy. Ronald New York. Leopold, L.B., Wohnan, M.G., Miller, J.P. (1964). Fluvial processes in geomorphology. Dover New York. 

A. Sundborg, The River Klar-elven, Study of Fluvial Processes, Geografika Annaler., Stockholm, 38(2-3) (1956). 

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