River Landforms

Question 1

What is a river basin?

Answer 1

Area surrounding a river,where any rain falling on the land makes its way into that river

Question 2

What are features of river basins?

Answer 2

1. A tributary is a smaller river that joins a main river
2. Source is where a river starts in an upland area
3. The mouth is where a river flows into the sea

Question 3

How are V-shaped valleys formed?

Answer 3

1. In the upper course of the river, fast flowing water because of heavy rain causes loose particles and boulders to be transported and scraped along the river bed.
2. This causes downwards erosion by abrasion
3. The valley sides are exposed to freeze-thaw weathering, material falls into the river
4. Causes further erosion
5. River doesn’t have enough energy to erode laterally so it erodes vertically.

Question 4

How are waterfalls and gorges formed? Upper course

Answer 4

1. They form when a river flows over an area of hard rock followed by soft rock
2. Soft rock is eroded by HA and abrasion, makes a step
3. As water goes over it, erodes more and more of soft rock
4. The hard rock is undercut by erosion, unsupported, collapses
5. Collapsed rocks swirled around eroding, creating a deep plunge pool
6. More undercutting, creates a steep-sided gorge.

Question 5

How are meanders formed?

Answer 5

1. The current is faster on the outside of the bend, river channel is deeper, (less friction to slow water down)
2. So more erosion takes place on the outside of the bend, forming river cliffs
3. The current is slower on the inside of the bend because the river channel is shallower
4. Eroded material is deposited on the inside of the bend, forming slip off slopes.

Question 6

How are ox-bow lakes formed?

Answer 6

1. Erosion causes the outside bends gets closer, until there is a small bit of land left
2. During a flood, the river breaks through this
3. River flows along the shorter course
4. Deposition eventually cuts off the meander
5. Forming an ox-bow lake.

Question 7

What is a floodplain?

Answer 7

Flat areas of land that flood

Question 8

How are floodplains formed?

Answer 8

1. When a river floods on the floodplain, the water slows down and deposits the eroded material
2. This builds up the floodplain
3. Meanders move across the floodplain, making it wider
4. Meanders migrate downstream, flattening the valley floor
5. The deposition that happens on slip off slopes of meander also builds up the floodplain.

Question 9

What are levees?

Answer 9

Natural embankments

Question 10

How are levees formed?

Answer 10

1. During a flood, eroded material is deposited over the whole floodplain
2. The heaviest material is deposited closest to the river channel
3. Over time, the deposited material builds up creating levees.