River transportation cannot occur without the presence of sediments. Normally, the sediments result from exogenetic or endogenetic sources. Exogenetic sediments refer to the ones gotten from outside the river, and it results from gully erosion, mass movement, sheet erosion and rill erosion. Endogenetic sources include materials within the river, which includes sediments from banks and stream beds. This is influenced by the resistance of the material to erosion and the strength of the erosion (Cool U. K. , 2000).
The transportation of a load downstream is through several processes and sub processes, which ensures that the load is finally deposited. The load: Bedload, Suspended load and Dissolved load There are terms which are essential for an effective understanding of the geographical process of river transportation. The first one is the load, which is used to refer to all the rock particles that the rivers carry. The load is divided into three, bed load, which are large particles, and can only be transported when the river has got enough energy.
Bed load can either be endogenic or exogenic, and moves by saltating, sliding or rolling. Ordinarily, the bedload is larger than the suspended load. Suspended load refers to the small particles carried by water, and therefore makes the water look muddy (Slide Share, 2009). The load is carried with the river current body, and can include suspended bed material. This material includes medium and fine sands. Clay and silt are examples of materials which can be held in suspension. Thirdly, the dissolved load includes all invisible minerals that are carried in the water as a solution.
The minerals result from chemical weathering, mineral springs, erosion and pollution. The load is obtained from the river through two major sources. Firstly, about ninety percent of it results from the material gotten after the mass movement and weathering process has taken place. This material moves down the slopes of the valleys. Secondly, ten percent results from the banks and beds erosion along the river channels (Slide Share, 2009). There are certain factors that the river has to have so as to transport, materials effectively.
To start with, the supply and location of the load has to be taken into consideration. Additionally, the amount of load available is also important, as well as the type of load. The volume of the water in the transportation process and the rivers’ energy is important too (Slide Share, 2009). Stream competence and capacity In relation to the energy of the stream or river, stream capacity and stream competence are important factors. Stream capacity refers to the total load that any river can carry at a specific time.
Once the load increases, the capacity increases also. Stream competence refers to the maximum weight or size of material that any river can transport. Generally, the competence of a river increases when there are floods, as it is able to carry big particles effectively (Slide Share, 2009). Therefore, competence and capacity increases downstream, during times of floods and every time the discharge increases. There is a way that geographers use so as to study the relationship between a river’s velocity and the particle sizes that can be transported.
This is revealed by the Hjusltrom curve, which is usually in form of a graph. It clearly portrays the velocity that is needed for erosion to occur as well as the velocity needed for the material to settle. In other words, the curve is used to reveal the erosion velocity (Slide Share, 2009). The major factor that impacts the stream competence and capacity is the slope of the channel. This is also referred to as the gradient. It is measured as “the difference in stream elevation divided by the linear distance between two measuring points” (Science J.
Rank, 2010). The water flow velocity is directly affected by the slope of the river channel. The greater the channel slope, the greater the velocity. In turn, the increase of river capacity affects the competence of a river (Science J. Rank, 2010). For instance, along Mississippi River, there is a near level delta at the lower end. It is as a result of low stream competence and velocity. On the contrary, the Colorado River, which courses up to the Grand Canyon is as a result of a very high velocity, which in turn results to high stream competence and capacity.
Channelization of water also affects the stream competence and capacity. If a stream is narrow, there is an increase in velocity and vice versa (Science J. Rank, 2010). River Transportation Processes There are three transportation processes in a river. The first process is referred to as suspension. Here, very small silt and clay particles are carried in suspension. The larger the velocity and turbulence amount, the more the particles that can be picked up at a certain time. The materials held in suspension normally account for the largest part of a river’s load.
Ordinarily, the water in a river usually contains acids, for instance, carbonic acid from precipitation. In this process, there is a very fast process of dissolving the bed rock, and the material is transported in solution form. This process is not very common, except in areas where there is limestone (Cool U. K. , 2010). There are situations where the materials are very large (bedload). In such cases, they are not picked up by the current. As a result, there are two sub- processes involved when transporting them. The first one is the saltation process.
Here, the gravel and the pebbles are normally lifted up by the stream or river current, and are later bounced along the river bed in a hopping motion. The second process is traction, which involves large boulders sliding or rolling along the beds of a river. This transportation process is only experienced when there are heavy rains or floods (Cool U. K. , 2010). Conclusion From the discussion above, it is evident that river transportation is very important in the geographical field. If there would be no rivers in the world, then some parts would experience disadvantages like inadequate soils for agriculture.
Additionally, river transportation systems have also been disadvantageous because they have resulted to minor landslides. References Cool U. K. (2010). River processes and management. Retrieved June from http://www. s-cool. co. uk/alevel/geography/river-processes-and-management/river-processes. html Science J. Rank. (2010). Stream capacity and competence. Retrieved from http://science. jrank. org/pages/6541/Stream-Capacity-Competence. html Slide Share. (2009). River transportation & Hjulstrom curve. Retrieved from http://www. slideshare. net/jacksonthree/river-transportation-hjulstrom-curveSample Essay of EduBirdie.com