Rivers

Question 1

Step by step on forming an oxbow lake

Answer 1

• Meanders in river erode on the outside
• Outside erosion causes meanders to get closer together
• A flood causes a shorter route for the water to take
• Deposition on the edge of the new river cuts off the meander from water

Question 2

Step by step on forming of a meander

Answer 2

• Flow of river swings side by side
• Erodes the bank, undercuts, steep, river cliff on outside of bend
• Deposition on inside of bend makes slip off slope

Question 3

Step by step on forming a waterfall

Answer 3

• Soft rock erodes faster than hard rock
• Soft rock erodes upstream and undercuts the hard rock
• Bottom of waterfall is a plunge pool
• Undercut worsens then the overhang collapses due to gravity
• Retreats upstream, forms a gorge

Question 4

What river landforms are found in the upper course?

Answer 4

V shaped valley
Waterfall
Gorge
Interlocking spurs

Question 5

What river landforms are found in the middle course?

Answer 5

Meander
Oxbow lake
Flood plain

Question 6

What river landforms are found in the lower course?

Answer 6

Mudflats
Natural levees
Estuary

Question 7

How do the characteristics of the river change from the source to the mouth? (Include a case study)

Answer 7

CS: River Severn
Land gradient goes from 30 degrees to 3
Width goes from 1m to 70m
Depth increases from 15cm to 10m
Velocity increases from o.25m/s to 10m/s

Question 8

Define attrition

Answer 8

Rocks collide together and make them smaller, rounder and smoother

Question 9

Define hydraulic action

Answer 9

Water and air get into cracks and make them larger

Question 10

Define abrasion

Answer 10

Rocks are thrown at cliffs or banks from high energy water

Question 11

Define corrosion

Answer 11

Water dissolves and wears away banks

Question 12

What are the three steps to slumping?

Answer 12

1) Heavy rain lubricates the rock and makes it heavier
2) River erodes the bottom of the valley sides making them steeper
3) The steep slope slides down in rotational way

Question 13

What is soil creep?

Answer 13

The movement of objects in the earth down hills from particles of soil moving downhill and being eroded away by rivers

Question 14

Step by step on forming a natural levee

Answer 14

• Formed on a river that carries lots of sediment
• The river floods and the sediment is deposited on the edge of the river as the water has lost velocity
• More flooding causes higher levees
• Can be reinforced by humans to prevent floods

Question 15

How are interlocking spurs formed?

Answer 15

River finds the fastest route by curving around mountain bases and then eroding into them to make the spurs interlock

Question 16

How are floodplains formed?

Answer 16

A wide flat area of land around the river that has lots of sediment from rivers flooding and the water spreading over it

Question 17

What are the physical causes of flooding?

Answer 17

Intensity of rainfall
Length of rainfall
Snow melt
Relief
Shape of drainage basin
Size of drainage basin
Vegetation
Geology

Question 18

What are the human causes of flooding?

Answer 18

Deforestation
Burning fossil fuels
Putting tarmac down instead of gravel

Question 19

What is the HIC case study for floods, and the cause of flooding?

Answer 19

Boscastle, Cornwall, UK
16th August 2004
75mm of rainfall fell in 2 hours
Confluence of Rivers Valency, Jordan and Paradise

Question 20

What are the key impacts of the HIC case study flood?

Answer 20

• £50 million damage to houses businesses and land
• 100 cars swept away
• 58 properties flooded and 4 swept away
• 300m of sewage pipe blocked

Question 21

What is the LIC case study for floods, and the cause of flooding?

Answer 21

Mozambique, Africa
January to 22nd of February 2000
3 days of heavy rain, then 5 weeks
Cyclones hit in February
Water levels rose 8m in 5 days from 6 rivers

Question 22

What are the key impacts of the LIC case study flood?

Answer 22

• Many cases of cholera
• 250,000 peoples houses destroyed
• Cost £175 million to rebuild transport
• 83% of people work in agriculture- damaged crops
• Floods displaced rodents and snakes

Question 23

Name four river management strategies and whether they are hard or soft engineering

Answer 23

Dams- HARD
Flood walls- HARD
Washland- SOFT
Straightening the river- HARD

Question 24

What is one of the case studies for managing the effects of flooding, and why is it prone to flooding?

Answer 24

Khulna, Bangladesh

80% of Bangladesh is floodplains
Most land is under 10m above sea level

Question 25

What does the management scheme of reducing the effects of flooding involve?

Answer 25

• Lay ceramic tiles on the floor
• Rugs not carpets
• Stainless steel or plastic kitchens
• Main heating should be placed upstairs
• Electric sockets should be 1.5m above floor level
• Replace wooden window frames with synthetic ones
  (Not just for Bangladesh but other places too)

Question 26

What is the case study for preventing floods?

Answer 26

River Stour, Blandford, Dorset, UK

Question 27

What were the causes of flooding in Blandford?

Answer 27

Deforestation
Intense rainfall, Dec 1979, 5cm of rain in 24 hours
Small floodplains
Impermeable clay is the local geology
Flooding since 1756

Question 28

What methods were used to protect the river and were they cost effective?

Answer 28

In 1986, a flood wall and relief channel, flood bank, washland a pumping station was built
This cost £1.45 million but saved £1.6 million so was very cost effective