Unit 2 Rivers

Outline ways in which people alter building design to reduce the effects of river flooding.

electrical sockets situated at 1.5m up the wall (to reduce need for re-wiring after flood -boilers to be situated on the first floor so not damaged in a flood - some houses in places like Bangladesh built on stilts so raised above ground

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Outline how people undertaking planning to reduce the effects of river flooding

Land-use zoning used to identify areas at most risk of flooding and those which are less at risk – used to influence planning permission – responsibility of local govt (i.e. county councils in the UK). -Higher risk areas given over to low value uses

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Give 3 examples of hard engineering and 3 examples of soft engineering river management techniques

Hard Engineering – channelisation; embankments; flood relief channels; dams Soft Engineering – land-use zoning; afforestation; washlands

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Describe 3 effects of flooding in the 2004 Boscastle Floods

50 cars lost - Gardens, village green covered in deposits of silt and mud - 6 properties completely destroyed.

4 of 15

Describe and explain the formation of a meander

Outer bank has faster flow and therefore great erosion on the outer bank - creates a river cliff due to undercutting by lateral erosion - on the inner bend – slow flowing due to shallower, low energy zone deposition lead to slipoff slope forming

5 of 15

Describe and explain the formation of waterfall

Soft rock is eroded quicker than the hard rock – gradually the hard rock is undercut by hydraulic action and abrasion -force of the falling water creates a plunge pool -eventually the rock collapses - fallen rocks enlarge the plunge pool by abrasion

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Which river features are a product of both erosion and deposition processes?

Floodplains, Meanders and Ox-bow lakes

7 of 15

Name the typical features found in the upper course of a river

a. V-shaped valley b. Waterfalls and plunge pools c. Rapids d. Gorges

8 of 15

Describe and explain what happens to velocity with increasing distance downstream

Velocity – this is the speed of flow which increases with distance downstream (as there is less friction due to less contact between the river bed and its banks).

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Describe and explain what happens to gradient with increasing distance downstream

Gradient – this is the slope of the river bed) – will decrease as the river flows downstream as it passes from the upland area down to the lowland area where it enters the sea

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Describe and explain what happens to discharge with increasing distance downstream

Discharge – amount of water passing a given point in a given time – as the river goes downstream it is fed by more tributaries and therefore the discharge increases.

11 of 15

How and why does width and depth of a channel change from source to mouth

Width and depth increases – initially due to vertical erosion followed by lateral erosion as the river moves along its coast.

12 of 15

Explain what is meant by slumping in the context of rivers

Slumping – downslope movement of material when river erodes the bottom of the valley side undercutting the slope – causing materials from the valley side to move downslope (or undercutting of river bank – causing the bank to slump downwards).

13 of 15

Name and explain the processes of abrasion, attrition and corrosion in the context of rivers

Abrasion – caused by the scraping away of the river bed and banks by the load carried by the water. Attrition – occurs as rocks bang each other in the river channel – gradually breaking each other down Corrosion – dissolving of minerals in the rocks

14 of 15

Define the terms: (a) watershed (b) source (c) confluence

Watershed – marks the edge of a drainage basin (it is the highest point of land) Source – the starting point of a river Confluence – the point at which a smaller river (tributary) joins the main river

15 of 15

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Unit 2 Rivers

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