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7 Cards in this Set

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Parts of a River

Drainage Basin


The area drained by the main river and its tributaries, bounded by a divide or watershed. Also known as the catchment area.


Tributary


A smaller stream which joins a larger stream or river.


Source


The point where a tributary/river begins


Mouth


The point where the river comes to an end, usually when entering a sea.


Course


The path that a tributary/river flows from its source to its mouth.


River Confluence


The point at which two rivers or streams join.


Delta


A landform that forms at the mouth of a river from the deposition of sediment as the river flow leaves the mouth.


Distributary


A stream that branches off and flows away from the main river channel.


Levee


Floodplain

Erosion- CASH

Corrasion/Abrasion


The load of a river grinds against its bed and sides and slowly wears them away


Attrition


The load itself is broken into smaller pieces as it is thrown against the sides and carried along


Solution/Corrosion


The water dissolves certain minerals (e.g limestone), eroding rocks


Hydraulic Action


The water splashes against the sides and surges into cracks, sweeping away rock fragments that have been loosened

Transportation- TS^3

Traction


Larger and heavier rocks or gravels are dragged or rolled along the bed


Saltation


Smaller and lighter rock fragments and sand hop and bounce along


Suspension


Fine particles such as silt and clay float along


Solution


Some minerals are transported in dissolved form

Waterfall

It is formed by the presence of a band of resistant rock in the course of a river. Through differential erosion, the less resistant rock that lies downstream will be eroded faster than the band of resistant rock by the force of the water and the rocks carried by the river hitting against the river bed, which is corrasion. This results in a sudden steepening of the river bed, causing the vertical fall of water known as a waterfall.

Rapids

When a river flows over an area of alternating bands of gently inclined resistant and less resistant rocks, the less resistant rock is eroded much faster. This would result in falls of water along a part of a river. The river flows swiftly when it flows over the outcrops of the resistant rock.

Meander

When the river flows over the shallower sections, its velocity decreases because there is greater friction between the water and the channel bed. When the water flows over the deeper sections, its velocity increases as there is less friction between the water and the channel bed.


The increase in velocity in a meander causes the water to flow in a spiral motion that erodes the concave bank, resulting in the formation of river cliffs and deposition on the convex bank, resulting in the formation of slip-off slopes.

Oxbow Lake

Continuous erosion of the concave bank and deposition on the convex bank of a meandering river cause the formation of a very pronounced meander with two concave banks getting closer.


The narrow neck of land between the two neighbouring concave banks would be cut through by either lateral erosion of the two concave banks or the strong currents during a flood. When this happens, a straighter river channel is created and an abandoned meander loop, called a cut-off, is formed. When deposition finally seals off the cut-off from the river channel, an ox-bow lake is formed.