How the source erosion of rivers lengthens river valleys

During the development of rivers or gullies, due to the intensification of water current, down-cutting erosion not only deepens the riverbed or gully bed, but also causes the erosion of the eroded parts to the upstream source with the erosion of the material. Also known as source erosion. Traceable erosion is also known as source-based erosion.

It is the erosion that lengthens the river in the direction of the source, mainly at the head of the valley. When the erosion datum is lowered for some reason, significant traceable erosion can also occur from the estuary section to the upstream direction.

The water flow drives small rocks, sand and mud from the bottom of the river and washes them out. In the process of flowing, the process of deepening, widening and lengthening the riverbed with its own dynamic power (vitality) and the destruction of the sediment carried by it.

Rivers, also known as surface runoff, usually have a certain flow velocity. There are many reasons for the formation of river erosion, including the mechanical impact of flowing water, the dissolution of water, and the abrasive effect of sand and gravel carried in water. Usually, the upper or middle reaches of rivers pass through mountainous areas, where the water is turbulent and the channel is narrow, and the erosion of the river mainly leads to the erosion of the river bed.

Because of this, waterfalls and gorges are often found in the middle and upper reaches of the river. The lower reaches of rivers are usually located in plains, with gentle terrain and slower flow rates. Due to the Coriolis force generated by the rotation of the earth, the water flow on the outer side of the river channel is faster, and over time, strong lateral erosion is formed on the outer side of the river.

As a result of lateral erosion, the channel takes on an attractive curved shape called a meander. [4] River erosion includes erosion, abrasion, and dissolution. Erosion Erosion is the erosion of the river bank caused by the erosion of the water flow, carrying away sediment and gravel.

Abrasion refers to the progress of the coarse-grained debris being carried in a rolling or jumping manner, abrasive the riverbed and bank wall along the way, and the sand and gravel also collide and grind with each other, making the particle size smaller and the roundness higher (this is also the case with the action of waves, currents, currents and wind); Fine-grained silt and clay are suspended and transported. Dissolution refers to the process of chemical erosion of soluble rocks by water. When the water contains CO2, it has a strong dissolution ability, especially in the soluble rock area (such as limestone area).

River erosion can be divided into downward erosion, lateral erosion and source erosion according to the direction of action. Downward erosion deepens the riverbed, carving out magnificent canyons in the upper mountains. By-erosion widens the river valley to form meandering and wide valley floor plains in the middle and lower reaches.

Source erosion lengthens rivers towards their sources.

Caused by prolonged impact.

Type: Traceable erosion: Erosion towards the source of the river. Downward erosion: Downward erosion perpendicular to the ground level. Lateral erosion: Erosion perpendicular to the banks of the river, that is, erosion of both banks.

Impact on the river valley: Traceable erosion: Extending the valley upstream. Downward erosion: deepens the riverbed, generally forming a V-shaped valley. Lateral erosion: widens the valley and widens the river horizontally.

There are three situations (all in places with slow flow rates such as plains).

1. Physical erosion.

1 Burial in the concave and convex banks of the river If the river channel is curved, the inertial river affected by the flow of water will erode the concave bank and the convex bank of the river will be deposited.

2 In plain areas, sediment deposition occurs on the riverbed due to the slow flow rate of the river bend, but the river erosion occurs under the formation of the riverbed due to the geostrophic deflection force (less geostrophic deflection force in the low latitudes, not in the equatorial region), that is, one side of the riverbed is deeper and the other side is shallower.

2. Chemical attack.

1 In fact, if there are limestone rocks on the riverbed and bank in places with slow flow rate, erosion will also occur, such as karst landforms, where carbon dioxide in the air and water combine to form carbonate and dissolve limestone, and at the same time, sedimentation is also going on because of the slow flow rate, but it is sand and rocks that are eroded.

In fact, river erosion is at any time, even if your royal talk about vegetation protection is good and the flow rate is slow, but the sedimentation can only be in the place where the flow rate is slow, and the slow flow rate can be used as a quantitative (this is the control variable method) to meet the sedimentation conditions, and whether there will be flowing water erosion in the slow flow rate area can be analyzed, so it is actually very common for the sedimentation and erosion of the river to occur at the same time in life.

According to the direction, the erosion of rivers can be divided into three types: traceable erosion, lateral erosion and pre-temporal erosion. 1.The erosion of river water on the surface is multifaceted.

In addition to constantly widening and deepening the river, it also has an erosive effect on the headwaters of the valleys and valleys, and constantly repents that the headwaters of the rivers are moving upwards and lengthening the valleys. This erosion is called traceable erosion; 2.Lateral erosion refers to the effect of flowing water to widen the riverbed.

Lateral erosion mainly occurs at the bend of the riverbed, because the main stream line is close to the concave bank, and due to the lateral circulation, the concave bank is eroded by the flowing water, and as a result, the riverbed is widened, and the river channel is more curved and meandering. 3.Downward erosion refers to the phenomenon that the bottom of a valley or valley is eroded by water flow for a long time, and the trench and riverbed develop in the direction of depth. As the river bed deepens, the water level decreases, so that the floodplains on both sides of the river are above the flood level and transformed into terraces on both banks.

River erosion refers to the destruction of surface rocks and their weathering products by rivers, and the erosion and destruction of rivers on their boundaries by relying on their own kinetic energy can be divided into sheet erosion on slopes, linear erosion of valleys and rivers, and linear erosion can be divided into traceable erosion, downcut erosion and lateral erosion.

A river is a depression caused by precipitation or water gushing out of the ground that collects in a low-lying part of the ground and flows regularly or periodically under gravity along the depression caused by the flowing water itself.

There are various principles for the classification of rivers, which can be divided into endorhes and outflow rivers according to the place of inflow, with endoric rivers flowing into inland lakes or swamps, or disappearing into deserts due to infiltration and evaporation, and outflow rivers flowing into the ocean.

In China, rivers are often classified according to the intra-year dynamic differences of river runoff, which are divided into seven types: Northeast China, North China, South China, Southwest China, Northwest China, Inner Mongolia and Qinghai-Tibet Plateau.

River erosion refers to the destruction of surface rocks and their weathering products by rivers. The erosion and destruction of the boundary of the river by relying on its own kinetic energy can be divided into: sheet erosion on the slope; Linear erosion of valleys and rivers.

Linear erosion can be divided into traceable erosion, undercutting erosion and lateral erosion.

The slash sensitive brushing and destruction effects of the river on its boundary by relying on its own kinetic energy are divided into: sheet erosion on the slope surface; Linear erosion of valleys and rivers. Linear erosion can be divided into traceable erosion, undercutting erosion and lateral erosion.

The river erosion landforms include the "V" shaped valley of the river Shanglingshenzhiyou, the waterfalls, the filial piety landform of the Loess Plateau, and the karst landform.

The erosion of flowing water is strong and widespread, about 90% of the continental area is under the control of the erosion of flowing water, precipitation erodes the surface of the earth, the flow of valleys and rivers, widens and deepens the valley floor and river bed, and the flowing water on the slope washes the entire slope surface, making it tend to be broken. For example, the Loess Plateau in China has been damaged due to vegetation and serious erosion by flowing water, resulting in a surface morphology of thousands of ravines.

The erosion and destruction of the boundary of the river by relying on its own kinetic energy, including erosion, abrasion and dissolution. According to the direction of action, it can be divided into: downward erosion, side erosion and traceable erosion.

The river water has kinetic energy, the flowing river water mechanically scours the surface rocks and gradually strips them, and the sand and gravel carried in the river water are also constantly rubbing and impacting it, and the river water can dissolve the rocks when the river flows through the distribution area of soluble rocks. The strength and variation of erosion are determined by the intensity of the riverbed flow and the erosion resistance of the river boundary. According to the direction of action, it can be divided into three types: downward erosion, side erosion and traceable erosion.