River Landforms

Question 1

How are Interlocking Spurs formed

Answer 1

In the upper course of a river, water and the material it carries cut into the river bed, creating a steep-sided V-shaped valley
The river is not powerful enough to erode laterally through areas of hard rock so it winds and bends around these rocks
The winding path of the river creates a winding valley of interlocking spurs

Question 2

How are Waterfalls and Gorges formed

Answer 2

1. Soft rock is eroded easily through hydraulic action and abrasion, enabling the river to cut down into the channel
2. Over thousands of year, the river continues to erode the soft rock, and a pluge pool develops
3. The overlying hard rock (cap rock) is undercut and left unsupported until it eventually collapses
4. The falling hard rock causes further erosio through abrasion, and the waterfall begins to retreat upstream

Gorges: As erosion continues, the waterfall retreats upstream, leaving a steep-sided valley downstream. This is known as a gorge

Question 3

How are meanders formed

Answer 3

When a river gets nearer to the sea, large bends called meanders to develop as lateral erosion occurs. Different processes occur on either side of a meander

Deposition: Deposition takes place on the inside of the bend, where the river flows slowly. The shallow channel creates greater friction, which slows the river down. Sand and shingle are deposited on the inside of the river bend, forming slip-off slopes

Erosion and Transportation: Erosion and transportation take place on the outside bend, where the river flows fast. The deeper channel creates less friction, which enables the water to flow quickly. Over time, erosion cause the riverbanks to be undercut and worn away, forming river cliffs

Question 4

How are Oxbow lakes formed

Answer 4

Oxbow lakes are formed from meanders. However, they are only found in the lower course of a river, where deposition becomes the dominant process.
1. Erosion on the outside bend of a meanders causes the neck of the meaner to become narrower
2. The neck of the meander continues to narrow until the river eventually breaks through to form a new river channel
3. The river now flows along the shortest course, bypassing the loop
4. As sediment is deposited on the riverbanks, the meander becomes sealed off.
5. An oxbow lakes forms.

Question 5

How are floodplains formed

Answer 5

Floodplains are wide, flat areas of land found on either side of a river. They are extremely prone to flooding.
When a river floods, material being carried by the river is deposited on the floodplain. Over time, this raises the height of the floodplain.
Floodplains are also made wider due to the migration of meanders.

Question 6

How are Levees formed

Answer 6

Levees are naturally raised river banks that form when a river repeatedly floods and deposits sediment

Question 7

How are Estuaries formed

Answer 7

Estuaries are found where the tidal mouth of a river meets the sea. Most formed at the end of the Ice Age, when the seals levels rose and caused widespread coastal flooding.
Estuaries are flooded daily by the tides as they rise and fall. At high tide, the incoming tide meets the outflowing river and reduces its velocity. This causes the river to deposit its sediment (sand and silt) over the floor of the river valley
Repeated flooding causes layers of sediment to build up over time, creating wide mudflats and salt marshes, which become exposed at low tide