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Fluvial Processes
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Abrasion
A form of mechanical weathering where particles in the moving water rub against the bedrock, wearing it down and contributing to the erosion process.
Alluvial fan formation
Occurs when a high-gradient stream exits a narrow valley onto a broad, flat plain, rapidly decreasing in gradient and depositing heavy sediments to form a fan-shaped wedge.
Corrosion
Also known as 'solution', it refers to the chemical dissolution of soluble minerals from the bed and banks into the water of a river, contributing to erosion.
Pothole formation
Circular holes in the riverbed formed by the abrasive action of pebbles and stones whirling around in an eddy, gradually drilling into the bedrock.
Weathering
The breaking down of rocks at the Earth’s surface, by the action of rainwater, extremes of temperature, and biological activity. It does not involve the movement of material.
Levee formation
Occurs when a river overflows its banks, and sediment is deposited closer to the river channel on both sides, building up higher ground known as levees.
Stream piracy
A process through which one stream captures the headwaters of another stream. This can occur due to headward erosion by the pirating stream, a drop in base level, or natural damming of the other stream.
Braiding
A river channel pattern involving networks of small, interlinked channels separated by temporary, often mobile islands or bars. It forms when sediment load is so high that some of the sediments are deposited midstream, creating new channels.
Erosion
The process by which soil and rock are removed from the Earth's surface by exogenic processes such as wind or water flow, and then transported and deposited in other locations.
Delta formation
A process resulting from the deposition of sediment carried by a river as the flow leaves its mouth and enters slower-moving or standing water. This sediment deposition can create landforms such as deltas.
Plunge pool
A deep depression in the riverbed at the base of a waterfall created by the impact of falling water and the swirling sediment it carries.
Headward erosion
The upstream extension of a stream channel into its source area. This process lengthens the river and can alter the drainage pattern.
Interfluve
The higher land or ridge that separates two adjacent river valleys or drainage basins. It affects fluvial processes by directing surface runoff into different river systems.
Meander formation
The process by which a river erodes laterally to form large bends known as meanders due to the horizontal movement of water, causing erosion on the outer banks and deposition on the inner banks.
Floodplain
Flat areas of land adjacent to a river that are subject to periodic flooding. They form as a result of both vertical and lateral erosion and are characterized by rich soil good for agriculture.
Entrenched meanders
Meanders that remain entrenched in a valley floor when the land is uplifted or the base level of the river is lowered, causing the river to carve downward into its floodplain.
Hydraulic action
The process by which the force of water against a rock surface can induce mechanical weathering and eventually lead to erosion of the river banks.
River terrace formation
Step-like landforms that flank the sides of valleys, which signify previous river levels before episodes of river incision. They form as a result of changes in the base level or river discharge.
Anabranching
Occurs when a river divides into branches and rejoins downstream, forming stable, multiple channels separately that flow for some distance. It affects landforms by dividing and re-depositing sediments.
Incised meanders
Meanders which cut deeply into the landscape, displaying a discordant relationship between the meandering river channel and the surrounding terrain. They reflect a history of changing water volumes, uplift rates, or a drop in the base level.
Base level
The lowest point to which erosion by running water can occur. It represents the limit for river erosion and is typically the level at which the river flows into the sea or a lake.
River rejuvenation
Occurs when the base level of a river drops or the land is uplifted, prompting the river to incise into its own floodplain, which adjusts the river's gradient and creates terraces.
Channel pattern change
The alteration of a river channel from straight to meandering or braided due to variations in sediment load, water volume, bedrock resistance or vegetation changes.
Deposition
The laying down of material carried by rivers, wind, ice, or ocean currents. This process can create a variety of landforms, like deltas, floodplains, and alluvial fans.
Transportation
Movement of sediment downstream by the water flow in a river. It shapes the landscape by redistributing sediments from one place to another.
Attrition
A form of erosion caused by the collision between sediment particles being carried by river water, which slowly reduces their size and makes them rounder.
Ox-bow lake formation
The process where a meander from a river is cut off, creating a free-standing body of water. This occurs over time due to the deposition at the meander's neck and erosion at its outer bend.
Nickpoint migration
The movement of a sharp change in channel slope, such as a waterfall or a rapid, upstream over time. It is due to the erosion that occurs at the base of these formations.
Hydrological cycle
The continuous movement of water on, above, and below the surface of the Earth. It influences fluvial processes by governing the water supply.
Water Table
The underground boundary between the soil surface and the area where groundwater saturates spaces between sediments and cracks in rock. It affects the base flow of rivers and thus fluvial processes.
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