The lower course of the river Starter: Quick revision of the key terms

What is erosion? I am a type of erosion that is like sandpaper How does Hydraulic action work? I am the type of erosion that knocks off edges off rough rocks. What is solution/corrosion? What is weathering? How does physical weathering work? Plants and animals break the rock apart- what am I? The slowest form of mass movement

List 3 characteristics of the lower course DONE DONE

How are floodplains formed?

How are floodplains and levees formed? Floodplains and leveés are formed by deposition in times of river flood. The river’s load is composed of different sized particles. When a river floods it deposits the heaviest of these particles first. The larger particles, often pebble-sized, form the leveés. The sands, silts and clays are similarly sorted with the sands being deposited next, then the silts and finally the lightest clays. Every time the river floods deposition builds up the floodplain.

Floodplain formation This is a cross section of a floodplain.

TASKS Draw annotated diagrams of how levees and floodplains are formed pg 71 2. Write a step by step explanation of how: Waterfalls Meanders Levees are formed 3. Complete activities on pg 70 and 71

How are Deltas formed? Deltas are found at the mouth of a river, where the river meets the sea. At this point the river is carrying too much load for its velocity and so deposition occurs. The top of the delta is a fairly flat surface. This is where the coarsest river load is dropped. The finer particles are carried into deeper water. The silt is dropped to form a steep slope on the edge of the delta while the clay stays in suspension until it reaches the deeper water.

How are Deltas formed?

Key ideas on the middle and lower course of rivers. Deposition is the main process operating in the middle and lower upper course of a river. Erosion is still important and occurs laterally (side to side). Discharge is greater than at the source. River Velocity is greater than at the source. Meanders and Oxbow lakes are formed by erosion and deposition. Deltas and leveés are formed by deposition.

Examination question Study the photograph below: B A C Features – a key word that often comes up in examination questions. Answers expected here are A = slipoff slope B = Floodplain C = rivercliff. Name the 3 features labelled A, B and C (3) Choose one of the features and explain its formation. You may use diagrams to help you.(6)

In pairs- write notes to answer: Describe how landforms change from source to mouth. (6 marks)

Time to test your understanding

How are the river landforms formed?

How much do you know about rivers?

Which of the following landforms are the result of a mixture of erosion and deposition? (2 marks) deltas meanders floodplains waterfalls leveés oxbow lakes rapids v-shaped valleys interlocking spurs