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Flashcards in Rivers & Coasts Deck (51)
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1

River Landforms

V-Shape valleys
Waterfalls & Gorges
Meanders & Ox-bow lakes
Floodplains & Delta

2

Coast & River processes

Erosion
Transport
Deposition

3

Formation of a V-Shaped valley

Steep gradient in Upper slope
Faster velocity of water
Vertical erosion is caused as a result
The sides also get weathered

4

Formation of a Waterfall

Hard + soft rock
River reaches soft rock and erodes vertically
Forming Waterfalls & Rapids
Turbulent water at base erodes = plunge pool
Until lip of harder roc is unsupported and falls

5

Formation of Gorges

Waterfall retreating

6

Formation of Meanders

Erosion inside + deposition outside

7

Formation of Ox-bow lakes

Continuous erosion of neck of meander
River takes easier usually straighter course
Deposition blocks off old meander

8

Floodplains

Flat valley floors on the banks of rivers which are layered with silt & alluvium left by the river flooding

9

Deltas

Sediment built up in layers

10

Types of transportation of eroded sediment in rivers

Traction- rolled
Saltation- bounced
Suspension- floated
In solution- dissolved

11

River case studies

Boscastle flood (2004) - MEDC
Bangladesh - LEDC

12

Causes of Boscatle flood

Saturated Soil
Torrential rainfall (500 mm in 4 hrs)
Small flood plain
Impermeable hillsides
Steep sided valleys running down Boscastle
Located at a confluence of Valency + Jordan

13

Effects of Boscastle flood

25 businesses destroyed
50 buildings damaged
4 footbridges destroyed
Tourist industry destroyed
Pavements & Gardens damaged
Stress + anxiety of locals
Insurance companies paid out £20 m.

14

Responses of Boscastle flood

Rescue helicopters
Widened & deepened river
Defence walls
Removed trees
Raised land around the river
Improved drainage

15

Causes of flooding in Bangladesh

Flood plain
Confluence of Ganges, Brahmaputra + Meghna
Monsoon season
Melting snow + ice from Himalayas
Deforestation

16

Effects of flooding in Bangladesh

766 dead
36 m. affected
Dhaka flooded with sewage
Overtopped many flood protection embankments

17

Responses to flooding in Bangladesh 1

Preparedness programme (Oxfam)
Cluster villages raised 2m above water level
Individual houses raised 2m
Food shelters where livestock can be brought along
Rescue boats
Radios to issue flood warnings

18

Responses to flooding in Bangladesh 2

Dhaka Integrated Flood Protection Project
Embankments
Slope protection
Drains
Sluice gates

19

Coastal landforms

Headlands
Bays
Wave cut platform
Caves
Arches
Stacks
Stumps
Beaches
Spits
Bars
Lagoons
Cliff

20

Types of Erosion

Hydraulic action - Water forced into cracks. Compressed air forces rock apart
Abrasion - sediment thrown at cliffs weathering them away
Solution - rock material dissolved by weakly acidic sea water
Attrition - Loose sediments knocked around into smaller and rounder particles

21

Formation of a WCP

Sea erodes base of cliff and undercuts it
Becomes unstable
Top of cliff collapses
result in a WCN
Continuous erosion of it leads to a WCP

22

Formation of cave, arch and stack

Water gets into cracks + through Hydraulic action enlarges
Repeated erosion forms a cave
More erosion forms an arch
The roof of the arch finally collapses

23

Formation of Bay + Headland

Coastline made from H & S rock eg. Granite and Chalk
Sea constantly erodes coastline
The S is eroded faster, forming a Bay + leaving the H to jut out as a headland

24

What is Swash

The force of waves bringing sediment up a beach

25

What is Backwash

Movement of water down a beach by the action of gravity. Moves sediment back towards the sea

26

What are Constructive waves

Strong swash
Weak backwash therefore allowing beach material to build up

27

What are Destructive Waves

Weak swash
Strong backwash therefore more material is eroded or taken away

28

What is LSD

The movement of sediment along the coast by the action of waves

29

Formation of a Tombolo, Bar + Lagoon

A tombolo is formed when the spit continues to grow until it reaches an island (like a bridge)
A bar is formed when a spit grows out to join up two headlands
The water inside is a lagoon

30

Formation of a Marsh

A Marsh is formed when sand shingle and mud get trapped behind the spit or bar and new land starts to form. eventually grass + plants grow on this stabilising it