Rivers

There are several processes at work in a river landscape and so it useful to get some key definition in place from the start. These definitions will also appear in other topics that look at different landscapes such as glacial landscapes and coastal landscapes so they provide a great opportunity for retrieval and recapping. 

Weathering	Mechanical	This is when physical processes change the river landscape such as freeze-thawing.
	Chemical	Hen water interacts with minerals in the soil and rocks causing them to dissolve.
	Biological	When plants and animals change the river landscape for example roots growing along the river bank or animals burrowing into the river bed or bank.
Mass Movement	Sliding and slumping	A large scale movement of rocks, soil and other material in a downward direction
Erosion	Hydraulic action	Caused by the power of the water as it hits the river bank and bed. Air becomes trapped in the cracks and forces it to break apart.
	Abrasion	Caused by pebbles grinding along the river bank and bed like sandpaper.
	Attrition	Caused by the rocks being carried by the river knocking into each other which then causes them to break up and become smaller and rounder.
	Solution	Caused by the river dissolving certain types of rock such as limestone. (Also a form of transportation)
Transportation	Traction	This is when large, heavy pebbles are rolled along the river bed. Usually occurs at the source of the river as the load is heavier here.
	Saltation	This is when pebbles are bounced along the river bed. Usually occurs at the source of the river.
	Suspension	This is when smaller, lighter sediment is carried within the water. Usually occurs at the mouth of the river.
Deposition		This is when the river loses its energy and drops the load/sediment it has been carrying. This usually happens if there is shallow water, where the volume of water drops and at the mouth of the river.

 

Useful resources:  

https://www.bbc.com/bitesize/guides/zq2b9qt/revision/1 

The course of a river 

Rivers have 3 distinct areas: 

Upper course 

Middle course 

Lower course 

Each area has its own unique features created by the processes mentioned above. 

Upper course	Middle course	Lower course
V-shaped valley	Meanders	Braiding
Interlocking spurs	Ox-bow lakes	Deltas
Waterfalls and rapids	Gentle gradients	Estuary
Steep gradients		Flat land

 Upper Course 

The upper course is where the source of the river is found. It is characterised by steep V-shaped valleys and the river here is narrow with steep gradients. As the river runs over alternate hard and soft rock types erosional features such as waterfalls are formed. An example of this is High Force in Northumberland, where there is a layer of hard rock, whinstone, which lays on top of soft limestone layer. As the River Tees runs over the hard layer and drops down it undercuts the soft limestone below creating a waterfall.         

 

From: http://www.geography.learnontheinternet.co.uk/topics/river_upper_course.html 

 

From: http://www.geography.learnontheinternet.co.uk/topics/river_upper_course.html    

High Force, Northumberland, UK 

From:   http://www.highforcewaterfall.com/ 

Middle Course      

In the middle course of the river the valley becomes wider and flatter. The river has more energy and volume than it did in the upper course and due to lateral erosion the river channel becomes wider. In the middle course of the river because the valleys are wider features such as meanders and ox-bow lakes form.                                

 From: revision.co.zw    

Lower Course 

In the lower course of the river the area surrounding it is flat. The volume of the water is at its greatest as the river will have been joined by several tributaries along the way. In the lower course features such as floodplains and levees will be found. Due to the energy in the river being at its lowest deposition occurs and as a result deltas can form. 

 

 From: wingategeog.weebly.com 

 

Learning Activity Suggestion – Make a landscape in a box showing the 3 main sections of a river, or as a class give each group a section to make and then join them together. This could be linked with a presentation by each group about their section of the river. 

 

Next time we will look at Drainage Basins and the Water Cycle and a case study of a River basin in the UK