# 2.3 How does a river shape the land along its different courses?

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2.3 How does a river shape the land along its different courses?

Can you find these kinds of landform at the same place?
How do the characteristics of a river change along its course? Can you find these kinds of landform at the same place?

They are different in _________ and _____ _______.
What are the different sections along a river course? They are different in _________ and _____ _______. Upper course Middle course Lower course gradient river energy Relatively straight, with bends around obstacles Winding Big bends occur

What are the different sections along a river course?
Gradient of the upper course: ______ steep Gradient of the lower course: _______ Gradient of the middle course: __________ moderate gentle

What are the different sections along a river course?
The energy and work vary along the three courses, different landforms are formed! Therefore, different landforms are found at different sections along a river course. Upper course Middle course Lower course

Is this the impression you have for the upper course?
What landforms are formed at the upper course? How much energy is there? What do you think about the energy of river at the upper course when compared with the middle and lower course? (Greater / Less) The energy is less because: Is this the impression you have for the upper course? The catchment areas of the tributaries at the upper course is (large / small). The amount of the channel water is (large / small). Large boulders in the channel (increase / decrease) the channel roughness. (Much / Less) of the energy are used for overcoming friction.

What is the direction of the erosion at the upper course?
What landforms are formed at the upper course? What is the direction of the erosion at the upper course? What is the work involved? ________ erosion is the dominant work at the upper course. Vertical Headward erosion also occurs when water starts to gather. Because of the small river energy, the rate of erosion is (slow / fast). The cross-section of a valley at the upper course (Small / Large) load can be transported. Deposition is (common / rare).

Landforms at the upper course
What landforms are formed at the upper course? What are the landforms produced? Landforms at the upper course Interlocking spurs Rapids Potholes Gorges Waterfalls

How is the land shaped at the middle course?
How much energy is there? Do you know why? How much energy is there at the middle course when compared with the upper course? (Greater / Less). More tributaries are joining the river. The amount of river water (increases / decreases). The river energy (increases/ decreases). The channel becomes _________. The water flows ______. smoother faster

How is the land shaped at the middle course?
What is the work involved? The river flow is faster and with more energy. Why? (Erosion / Transportation / Deposition) What is the main work at the middle course? Erosion occurs, but there is extra energy for _____________. transportation

Landforms at the middle course
How is the land shaped at the middle course? What are the landforms produced? Landforms at the middle course Slip-off slopes River cliffs Meanders Bluffs

Is the energy large or small at the lower course?
What landforms are formed at the lower course? How much energy is there? Is the energy large or small at the lower course?

The cross-section of s valley at the lower course
What landforms are formed at the lower course? How much energy is there? It has the (smallest / largest) discharge among the three courses. The river bed is (smooth / rugged), so the friction here is greatly (reduced / risen). Therefore, the flows are at a (low / high) speed. The lower course has the (highest / lowest) energy. The channel here accommodates (less / more) water than that of the upper course. The cross-section of s valley at the lower course

What landforms are formed at the lower course?
How much energy is there? Does it mean the river energy is high all the time at the lower course? (Yes / No) The river energy drops when: the channel flow is blocked by sea water at the _______ of the river. mouth the amount of river water is reduced during the (wet / dry) seasons. flooding occurs and the flood water has not yet retreated from the valley floor.

What landforms are formed at the lower course?
What is the work involved? Ha! Ha! All three work occur at the lower course! What is the work at the lower course? Erosion- at the (inner / outer) banks of the river. (Erosion / Transportation / Deposition) Transportation- bringing the load towards the mouth of the river. Deposition- whenever and wherever speed of flow is lowered.

Landforms at the lower course
What landforms are formed at the lower course? What are the landforms produced? Landforms at the lower course Flood plains Deferred tributaries Oxbow lakes Deltas Levees Braided streams

Case study: How does the Chang Jiang change along different courses?
Tuotuo He Yichang Hukou Upper course Middle course Lower course

Do you know any characteristics of the Chang Jiang?
Case study: How does the Chang Jiang change along different courses? The longest river in China and ______ longest in the world. third Do you know any characteristics of the Chang Jiang? Average annual discharge: 30,000 m3/sec. The load is not heavy as compared with the __________. Huang He humid subtropical It flows past the ___________ _______ humid area of China. About % of the river water comes from _______. rainfall

Case study: How does the Chang Jiang change along different courses?
Middle course Lower course Upper course

What are the characteristics of the upper course of the Chang Jiang?
The river source: The Tuotuo He The discharge is small. Vertical erosion The Hutiaoxia at the Jinsha Jiang The gradient is gentle. The river flows slowly. At the Jinsha Jiang South-flowing. The channel winds through interlocking spurs. The gradient is steep.

What are the characteristics of the upper course of the Chang Jiang?
At the Sichuan Pendi More rainfall Many large tributaries join the main channel Discharge increases rapidly Great erosive power Forms Sanxia

What are the characteristics of the middle course of the Chang Jiang?
A big drop in _______ and the _________. altitude gradient Meanders are formed. 286 km Numerous lakes are found, e.g. Dongting Hu. Length of the river between them: 712 km

What are the characteristics of the lower course of the Chang Jiang?
The land is flat and low, e.g. the Chang Jiang Delta plain. The tributaries are shorter than those in the middle and upper courses. Many meanders and braided streams. Levees and deferred tributaries are found. Delta and lagoon are formed, e.g. Tai Hu.

How does a river basin work as a system?
What is a system? It is a group of things that interact within a boundary to perform some functions. It includes _______, __________ and ________. inputs processes outputs Open system Closed system Input Processes Output Energy Energy Energy Energy Matter Matter Boundary of the system

How does a river basin work as a system?
Inputs Processes Outputs  Weathering  Mass movement  Erosion  Interception  Drip flow/ Stem flow  Surface run-off  Infiltration  Subsurface run-off  Transportation  Deposition Radiation Absorption Conduction Solar radiation Heat Evaporation Channel outflow Water Precipitation Water Evapo- transpiration Vapour Exogenetic processes Rocks Transportation Sediment

The end

What are the landforms produced at the upper course?
1 Interlocking spurs They are the spurs interlocking with each other. The river has too little energy to remove obstacles, so the river water flows around them. Interlocking spurs Valley is deepened ________ erosion deepens the channel and makes the obstacles more marked. Vertical

What are the landforms produced at the upper course?
2 Gorges Downcutting is (slower / faster) than lateral erosion. This creates a (deep / shallow) and (narrow / wide) V-shaped valley, i.e. gorges.

What are the landforms produced at the upper course?
3 Rapids The river water is unable to erode the layer of _________ rock. resistant Rapids The river bed becomes (even / uneven). The turbulent currents are called rapids.

What are the landforms produced at the upper course?
4 Waterfalls Less resistant rock is eroded by river water at a (slower / faster) rate. Water flow Waterfall forms The river falls vertically down. Plunge pool forms The falling water produces strong _________ action, forming a circular hollow filled with water. Large angular boulders hydraulic

Which type of fluvial erosion is involved within the potholes?
What are the landforms produced at the upper course? Which type of fluvial erosion is involved within the potholes? Abrasion. 5 Potholes How does it form? What is this? Pothole When a river flows over an uneven surface, it causes ___________ in the water. turbulence A pothole is formed when the water drills with the load it carries.

What are the landforms produced at the middle course?
1 Slip-off slopes and river cliffs What are the two landforms produced? What are the work involved at the inner and outer bank? Which part of the river has the fastest flow? River cliff Inner bank: __________ deposition Outer bank: ______________ Slip-off slope lateral erosion Fastest part of the river flow River cliff Slip-off slope

What are the landforms produced at the middle course?
2 Meanders The outer bank gets worn away through _______. Inner bank Outer bank erosion Meander appears More convex More concave The inner bank builds up through __________. Lateral erosion creates river cliffs deposition Slip-off slopes form The river (bends/ straightens). Each bend is called a meander. Faster stream of water thrown towards outer banks Sediment Low river cliff

What are the landforms produced at the middle course?
3 Bluffs The meanders migrate downstream. Erosion at outer bank creates river cliffs They remove the interlocking spurs on their way through ________. erosion __________ at outer bank are pushed back and join into lines, forming bluffs. River cliffs Bluffs

What are the landforms produced at the lower course?
1 Flood plains The load is carried to the valley floors by the flood water. Repeated flooding and __________ build up a flat area. During floods, water overflows from the channel to the lands, bringing sediment with it _________ builds up on the river bed, silting occurs Sediment deposition The deposits on the flood plain are called ________. They are fertile and good for farming. Flood plain alluvium

What are the landforms produced at the lower course?
2 Levees The flood water overflows from the channel. The (small / large) load is dropped at the river banks. Levee The banks are (raised / collapsed). The levees are the ridge-like features at the river banks.

What are the landforms produced at the lower course?
3 Deferred tributaries Defferred tributary Tributaries flow _______ to the main channel. parallel They finally break through the ______ and join the main channel. levees

What are the landforms produced at the lower course?
4 Oxbow lakes This is an oxbow lake It is developed from a meander! Do you know how?

What are the landforms produced at the lower course?
4 Oxbow lakes Oxbow lakes are the product of active ______ erosion and ___________ in the river. Water flow Little water enters the old channel Sediment lateral Deposition deposition The meanders bend more.The (outer / inner) banks are pushed backward When two outer banks of two bends meet, a new channel is formed. Oxbow lake _________ silts the original channel. Sediment An oxbow lake is formed.

What are the landforms produced at the lower course?
5 Braided streams Water levels (rise / drop) during dry seasons. (Erosion / Deposition) forms low ridges and blocks the river flow. Braided streams In wet seasons, the river is forced to split into several separated channels. The braided streams rejoin

What are the landforms produced at the lower course?
6 Deltas A delta is a gently sloping platform of _________ gradually builds up and extends into the ____. sediment Onshore current Onshore current Onshore current Onshore current sea Mud-flat or marshes Distributary It is a fan-shaped mud-flat. Deposits New deposits during low-flow season Lagoon It is formed at the mouth of the river. Delta forms The velocity of flow (rises / drops) Onshore current

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