[Geography Notes] on Fluvial Process Pdf for Exam

The fluvial process is the physical interaction between the flowing water and the natural channels of flowing water such as rivers and streams. Such a fluvial process plays an essential and very significant role in the weathering of the land surfaces and the process causes the transportation which is known as fluvial transportation of the rock debris from higher to lower levels. Such fluvial transportation leads to the deposition and creation of landforms along the banks and at some distance from the edges of such flowing water bodies. 

Fluvial Processes and Its Effects

Most of the fluvial processes include the movement of the sediment as is clear from the fluvial processes definition. Such a movement of the sediments because of the flowing water causes erosion also known as fluvial erosion or deposition on the river bed which is a result of fluvial transportation. Thus, fluvial erosion meaning finds its basis in the fluvial processes definition. 

Fluvial erosion processes are carried out by the moving water mainly in two ways. The first manner in which the hydrology and fluvial geomorphology is determined is by the movement of water across the bed of the stream that exerts shear stress directly on the bed. If in some cases, the cohesive strength of the substrate is lower than the shear force exerted or there is a case in which the bed is formed of loose sediments that can be mobilized by such stress, then the steam bed will go low mainly because of the flow of clear water. But if the river maintains a significant quantity of sediment then the sediment material can act as a tool for the enhancement of the wearing of the bed. This process is known as abrasion. During this time, the fragments of the sediments themselves undergo weathering and the fragments become small and round which is known as attrition. Thus, both abrasion and attrition form a part in the determination of hydrology and the fluvial geomorphology.

Fluvial transportation of the river sediments is either caused by the bedload, which is formed by the coarse fragments that move close to the bed or are caused by the suspended load, which are the fine fragments carried with the flowing water. There is also some form of dissolved material that is flowing with the water in the river or stream affecting the stream geomorphology as well.

There is a specific velocity that is present for each grain of the sediment in proportion to its size. This velocity is known as the entertainment velocity which triggers it to move. There is no hard and fast rule that if the velocity of the sediment grain falls down below the entertainment velocity. The grain will continue to be transported by fluvial transportation processes such as the reduced or removed friction in-between the grains and the river bed. As the velocity decreases over time, eventually the sediment grain settles and gets deposited thus contributing to the hydrology and the fluvial geomorphology. 

As a river or stream moves continuously, it keeps on picking up and dropping solid particles of the rock and soil from the bed. It is observed that wherever the river flows towards the fast there is more possibility of the particles being picked up rather than being dropped while wherever the flow of water is slow, there is more possibility of the particles being dropped and deposited rather than being picked by the water. Thus, in this case, the rate of flow of the water determines the steam morphology. These areas where more such particles are dropped are known as alluvial plains or flood plains and the particles that are dropped are known as alluvium. Such alluvial deposits are also done by small streams but the most significant ones are the flood plains and the deltas of large rivers. 

Because of the fluvial erosion processes the amount of matter that is carried by the large rivers in enormous quantities. Because of such fluvial geography, the names of many rivers are derived from the colours that are obtained from the particles and matter moved by different types of fluvial erosion. An example of such an incident is the Huang He River in China which when translated means yellow river. Another one is the Mississippi River in the US which is also known as “the Big Muddy”. Another example, as given below in the image, is the White River in South Dakota which is known so because of the white colour derived from the sediments it carries.