River Processes and Landforms Flashcards
Describe what Hydraulic Action is
It is the force of the water hitting the river bed and banks. It is most effective when the water is moving fast and there is a lot of it.
What is Attrition
It is when stones carried by the river knock against each other, gradually making the stones smaller and more rounded, eventually forming sediment
What is Abrasion
When the load carried by the river repeatedly hits the side of the banks dislodging particles into the flow fo the river.
What is solution
When water flows over limestone or chalk, the rock is slowly dissolved. This is because the chalk and limestone is soluble in mildly acidic river water.
How do interlocking spurs form
As a river cuts down a valley some rock is harder then other rock. This makes the river bend round the harder rock creating a bendy river.
Explain how a waterfall forms
1) The rock is eroded faster then the hard rock which creates an overhang
2) Abrasion and hydraulic action erosion creates a plunge pool
3) Over time the overhang increases in time until the rock is no longer supported and collapses.
4) This process continues and the waterfall retreats upstream
5) A steep-sided valley is left where the waterfall once was. This is called a gorge.
How do meanders form
Meanders are produced when water in the stream channel erodes the sediments of an outer bend of a stream bank and deposits this and other sediment on subsequent inner bends downstream.
How do ox-bow lakes form
Over time meanders begin to erode towards each other. When there is a very high discharge, the river cuts across the neck of the two meanders creating an ox-bow lake
What is a floodplain
It is an area of land which is often covered by water when a river bursts its banks
What is a use of floodplains
They are often used as agricultural land as the soil is very fertile
What is an estuary
An estuary is where a river meets the sea. The river here is tidal and when the sea retreats the volume of the water in the estuary decreases in volume
What is a Levee
A levee is a raised river bed found in the lower course of a river.
How is a levee formed
It is formed over time as sediment brought from upstream during floods builds up on the sides of the banks, gradually increasing the sides of the river
What is a waterfall
A waterfall is a sudden drop along the river course.
