GCSE-ready- Home
- Lessons
- GCSE & IGCSE Geography A
- Rivers: processes and the long profile
Rivers: processes and the long profile
🎬 The doodle video for this lesson is coming soon. Subscribe on YouTube to see it first.
A river changes a lot between its source and its mouth. Its shape, speed and load all change in a predictable way.
Processes in the valley
Rivers erode by hydraulic action, abrasion, attrition and solution.
On the valley sides, weathering (freeze-thaw, chemical, biological) loosens rock, and mass movement (sliding and slumping) moves it into the river.
In the upper course erosion is mainly vertical (downwards); further downstream it becomes more lateral (sideways).
On the valley sides, weathering (freeze-thaw, chemical, biological) loosens rock, and mass movement (sliding and slumping) moves it into the river.
In the upper course erosion is mainly vertical (downwards); further downstream it becomes more lateral (sideways).
Changes downstream
From source to mouth:
Increase: width, depth, discharge, velocity and cross-sectional area.
Decrease: gradient and sediment size.
Sediment becomes smaller and rounder because of attrition.
The valley changes from a steep V-shape to a wide, flat floodplain.
Discharge = cross-sectional area × velocity, measured in cumecs (m3/s).
Increase: width, depth, discharge, velocity and cross-sectional area.
Decrease: gradient and sediment size.
Sediment becomes smaller and rounder because of attrition.
The valley changes from a steep V-shape to a wide, flat floodplain.
Discharge = cross-sectional area × velocity, measured in cumecs (m3/s).
A named river: the River Tees
The Tees rises on Cross Fell in the Pennines and flows east to the North Sea at Teesside.
In its upper course, High Force waterfall has formed where hard dolerite (part of the Whin Sill) lies on top of softer rocks.
In the lower course the Tees has large meanders, a wide floodplain and an estuary.
Storms increase discharge and erosion; long dry spells and droughts lower discharge, so the river deposits more.
In its upper course, High Force waterfall has formed where hard dolerite (part of the Whin Sill) lies on top of softer rocks.
In the lower course the Tees has large meanders, a wide floodplain and an estuary.
Storms increase discharge and erosion; long dry spells and droughts lower discharge, so the river deposits more.
A river is 4 m wide, 0.5 m deep on average and flows at 0.8 m/s. Find its discharge.
- Cross-sectional area = 4 × 0.5 = 2 m2
- Discharge = 2 × 0.8
Answer: 1.6 m3/s (cumecs)
Downstream: width, depth, velocity and discharge increase; gradient and sediment size decrease and sediment gets rounder. Discharge = cross-sectional area × velocity. Vertical erosion upstream, lateral erosion downstream.
Check you have got it
Answer 6 quick questions with instant marking. If you get one wrong, GCSE-ready shows you why and gives you another go. It is free, and you do not need an account.