Rivers & Drainage Basin (Cambridge (CIE) IGCSE Geography): Flashcards
Exam code: 0460 & 0976
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Define hydrological cycle.
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Cards in this collection (33)
Define hydrological cycle.
The continuous movement of water on, above and below Earth's surface in a closed system, where water is constantly recycled.
Water in the hydrological cycle is constantly ________ through stores and transfers.
Water in the hydrological cycle is constantly recycled through stores and transfers.
Define store in the hydrological cycle.
A place where water is held for a period of time, such as the atmosphere, lakes, aquifers or oceans.
The process by which water changes from a liquid to a gas due to heat from the sun is called ________.
The process by which water changes from a liquid to a gas due to heat from the sun is called evaporation.
What is interception in the hydrological cycle?
Interception is when precipitation is prevented from reaching the ground, usually by being caught on leaves or branches.
Define drainage basin.
The area of land drained by a river and its tributaries, also called the catchment area.
The boundary between two drainage basins is known as the ________.
The boundary between two drainage basins is known as the watershed.
Define confluence.
The point where two or more streams or rivers meet.
True or False?
A drainage basin is a closed system.
False.
The hydrological cycle is a closed system, but a drainage basin is an open system with inputs (precipitation) and outputs (evaporation, transpiration and flow to the sea).
Define hydraulic action.
The force of the water removing material from the bed and banks of the river.
What is the main difference between vertical and lateral erosion in a river?
Vertical erosion increases the depth of the river and is dominant in the upper course, while lateral erosion increases the width of the river and is dominant in the middle and lower courses.
When a river loses energy and can no longer carry its load, it _______ the material.
When a river loses energy and can no longer carry its load, it deposits the material.
Define a river's long profile.
A diagram showing the change in river gradient from source to mouth, usually with a concave shape.
Describe two characteristics of a river channel in the upper course.
The river channel in the upper course is narrow, shallow, and has steep valley sides with a rough channel bed.
In the lower course of a river, the channel is _______ and _______ than in the upper course.
In the lower course of a river, the channel is wider and deeper than in the upper course.
Define the Bradshaw model.
A model showing how river characteristics — discharge, width, depth and velocity — change from source to mouth.
According to the Bradshaw model, what happens to bed roughness and gradient as you move downstream?
Both bed roughness and gradient decrease as you move downstream according to the Bradshaw model.
The efficiency of a river is measured using the _______ radius, which is the cross-sectional area divided by the wetted perimeter.
The efficiency of a river is measured using the hydraulic radius, which is the cross-sectional area divided by the wetted perimeter.
Define saltation.
A transport process in which small particles bounce along the riverbed in the water flow.
True or False?
Abrasion is dominant in the lower course of a river.
False.
Abrasion is dominant in the upper course, deepening the channel.
How does a waterfall retreat upstream to form a gorge?
Soft rock beneath the hard rock is undercut; the hard rock collapses, the process repeats, and the waterfall retreats upstream, leaving a steep-sided gorge.
Define a pothole (in a river).
A round depression in the riverbed formed by abrasion, as trapped sediment spins in the flow and erodes the rock.
What is an oxbow lake?
A cut-off meander — during a flood the river breaks through the meander neck, and deposition seals off the old loop.
Define a slip-off slope.
A gentle slope of deposition on the inside of a meander, where the water flows more slowly.
Why do levees form along river channels?
When a river floods, the heaviest material is deposited first, nearest the channel, gradually building up natural embankments called levees.
Define an estuary.
A wide, deep river mouth where freshwater and saltwater mix, forming the transition between river and sea.
What conditions are needed for a delta to form?
A large sediment load and a rapid drop in velocity at the mouth, so sediment is deposited and builds up.
Define interlocking spurs.
Interlocking spurs are ridges of higher land that project into the valley from alternating sides in the upper course, where the winding river erodes around them.
How does a V-shaped valley form in the upper course?
Vertical erosion deepens the channel, then weathering and mass movement cause the valley sides to collapse into the river, forming a steep V-shaped valley.
Define a meander.
A meander is a bend in a river where erosion on the outer bank forms a river cliff and deposition on the inner bank forms a slip-off slope.
How does a floodplain form?
Meander migration widens the valley floor, and when the river floods it deposits sediment across the flat land, gradually building up a floodplain.
Alternating bands of hard and soft rock in the upper course erode unevenly to form ______.
Alternating bands of hard and soft rock in the upper course erode unevenly to form rapids.
True or False?
A delta forms where a river's velocity increases at its mouth.
False.
A delta forms where the river's velocity drops rapidly, causing deposition of the large sediment load it carries.
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