river landscapes

How are waterfalls formed and what river processes contribute to this

• when there is a drop in the river bed from one level to another

• This often happens due to changes in the hardness of rock, where hard rock overlies soft rock

• Hydraulic action and abrasion are the main erosional processes in waterfall formation

• The softer rock erodes quicker, undercutting the harder rock and creating a plunge pool

• This leads to the development of an overhang of hard rock which eventually collapses, falling into the plunge pool and making it deeper

How are v shaped valleys formed and what river processes contribute to this

• vertical erosion is dominant in the upper course of the river

• This cuts down into the river bed and deepens the river channel

• Weathering and mass movement was to material from the valley sides collapsing into the river forming a steep v-shaped valley

How are interlocking spurs formed and what river processes contribute to this

• in the upper course of the river the channel starts to meander

• Erosion happens on the outside of the bend

• In the upland areas this forms interlocking spurs

How are meanders formed and what river processes contribute to this

• in lowland areas lateral erosion is dominant, meaning meanders increase in size

• The fastest water flow is on the outside of the river bends, leading to erosion

• The erosion undercuts the over bank forming a river cliff

• The river bank collapses and the edge of the meander moves further out

• The slowest flow is on the inside of the river bends leading to deposition

• This causes wide flats flood plans on either side of the river as well as the meanders

How are oxbow lakes formed and what river processes contribute to this

• as the river travels down streams the size of meander increases

• The erosion on outside bends van eventually lead to the formation of a meander neck

• At a time of flood, the river may cut through the neck of the meander forming a straighter course for the water

• The flow of water at the entry and exit from the meander will then be slower, leading to deposition

• The meander becomes cut off from the main river channel forming an oxbow lake

How are floodplains and levees formed and what river processes contribute to this

• Flood plains are formed through the migration of meander across the valley

• Material is then added to the floodplain during times of flood

• As the water overflows increased friction reduces the velocity so material is deposited

• the heaviest sediment being carried is deposited first, right next to the banks of the river

• This forms large laters of sediment known as levees