Flashcards
C - Rivers
Cards in this deck (34)
- 1Define SourceThe original point from which the river flows
- 2Define MouthThe point where the river meets the sea
- 3Define TributaryA minor river flowing into the main channel
- 4Define confluenceThe point where 2 or more rivers meet
- 5Define LoadMaterials carried by the river
- 6Define River BedThe channel bottom
- 7Define BanksThe channel sides
- 8Define Cross profileThe side to side cross-section of a river channel and/ or valley
- 9Define Long ProfileThe gradient of a river, from its source to its mouth
- 10Define Upper courseSet in a landscape of high relief where the river begins as a trickle and flows down a steep gradient. You find waterfalls, rapids and v-shaped valleys.
- 11Define Middle CourseFurther downstream in an area of hilly rather than mountainous relief. Discharge is greater and so the channel is deeper. Volume of water is greater due to tributaries joining. Lateral erosion starts to occur so meanders are found.
- 12Define Lower CourseThe section closest to the river mouth, where the surrounding land is low-lying. Erosion is now mainly lateral, the gradient is almost flat. Meanders, ox-bow lakes, floodplains, levees are found here.
- 13Define River ChannelThe channel through which a river flows, created by lateral and vertical erosion.
- 14Define V-Shaped valleyThe shape of the valley created due to vertical erosion in the upper course.
- 15Define WaterfallSudden descent of a river or stream over a vertical or very steep slope in its bed. It often forms where the river meets a band of softer rock after flowing over an area of more resistant material.
- 16Define MeanderA pronounced bend in a river.
- 17Define Oxbow lakeAn horseshoe shaped lake which has been cut off from a meander river.
- 18Define Meander ScarThe scar in a landscape left behind following the meandering river.
- 19Define FloodplainThe relatively flat area forming the valley floor on either side of a river channel, which is sometimes flooded.
- 20Define LeveeEmbankment of sediment along the bank of a river. It may be formed naturally by regular flooding or be built up by people to protect the area against flooding.
- 21Define Vertical erosionDownward erosion of a river bend.
- 22Define Lateral erosionSideways erosion by a river on the outside of a meander channel. It eventually leads to the widening of the valley and contributes to the formation of the flood plain.
- 23Describe RapidsRapids are fast flowing turbulent sections of the river bed has a relatively steep gradient and uneven.
- 24How are rapids formed?Where there are alternating bands of hard and soft rock along the channel bed, differential erosion will occur as the soft rock is eroded quicker. This makes the river bed uneven and the rivers flow becomes turbulent resulting in white water sections called rapids.
- 25Describe Interlocking spursThe land has rocks of various resistances. The river winds its way around the more resistant rock and cuts down into the weaker rock.
- 26Describe a waterfallWhere the water falls down a vertical drop in the channel.
- 27Describe a gorgeA narrow steep sided valley with bare rocky walls. A recession gorge is one left behind a waterfall.
- 28List features of a waterfall.Overhang
Plunge pool
Fallen Rock
Steep sided gorge
Hard Rock
Waterfall retreat - 29How is a meander formed in detailIn the middle course, water in the straight channel flows around areas of deposited material (riffles) in the river bed and through deeper sections (pools).
The flow hits the river band and erodes it to create the outer bend.
Continued erosion leads to the formation of the river cliff on the outer bend.
High level - Some of the flow corkscrews along the bank to the inside bend, called helicoidal flow, where the current is slower so it deposits its load.
Deposition occurs on the inner bend due to a low velocity, called a slip off slope.
As the river bank erodes on the outer bend (lateral erosion) and material deposited on the inner bend, it results in an asymmetrical cross profile of the channel.
Continued erosion and deposition leads to the increased size of the meander as they move (meander migration) they flatten the land around the land around them to create a floodplain. - 30How is an oxbow lake formed in detailThe meander loop becomes very large, meaning only a narrow strip of land separates the river channel known as the meander neck, continued lateral erosion causes the meander neck to become increasingly narrow.
When a river floods the main flow of water cuts straight across the neck, this shortcut begins to breakdown the banks and carves a new channel.
Floods recede so the river reverts to its normal meandering channel, the process repeats over and over again with every flood event. This new channel becomes so established by the continued lateral and vertical erosion that it becomes the main channel.
The loop of the old river channel is increasingly detached as it is no longer receiving river water. Subsequently flooding causes deposition on the new river banks, aiding the detachment of the old loop. Marsh plants colonise the area which further widens the gap. In time only the far end of the meander loop is left, sometimes several meters from the main channel. - 31How are levees formedRiver flowing in the river channel carrying the river load. The size of the sediment then becomes progressively smaller with increased distance from the river. When a river bursts its banks friction with the land reduces the waters velocity and causes deposition. Heavier sediment is deposited closer to the river.
With each successive flood the banks are built up higher. Although it may seem that the levees may make it more difficult for the river to flood next time, this is not the case. This is because over time the bed of the river develops a thicker layer of sediment which raises the river in its channel. - 32How are floodplains formed?Floodplains form due to both erosion and deposition. Erosion will slowly move the bluff line creating a larger area. Lateral erosion due to meander migration widens the floodplain. When the river overflows material being carried is dropped as speed/energy is lost. Over time, this sediment forms layers on the floodplain, building it up to form a flat area.
- 33What is the difference between impermeable and permeable surfaces?Water cant go into the ground if its impermeable, however if it is permeable it water can enter the ground.
- 34What is a hydrograph?A graph which shows the discharge of a river, related to rainfall, over a period of time.
Information
- Description
- GCSE Geography (Paper 1) Flashcards on C - Rivers, created by David Ellis on 12/12/2018.
- Created by
- David Ellis
- Views
- 1
- Rating