QUESTION 1 - WATER

QUESTION 1 - WATER

Key areas of study for this question:

  • River processes
  • River landscapes / features
  • Diagrams and annotations for key features - Meanders and Waterfalls
  • Tourism issues
  • Flooding in MEDC's and LEDC's
  • Management / Prevention of flooding
  • Flood Hydrographs

This is the question where the exam board can ask map skills questions - so make sure you also revise your 6 figure grid references! (See attached PowerPoint at the bottom of this page)

RIVER PROCESSES

 

Erosion

Erosion involves the wearing away of rock and soil found along the river bed and banks. Erosion also involves the breaking down of the rock particles being carried downstream by the river.

 

The four main forms of river erosion:

  • HYRAULIC ACTION - The force of the river against the banks can cause air to be trapped in cracks and crevices. The pressure weakens the banks and gradually wears it away.
  • ABRASION - Rocks carried along by the river wear down the river bed and banks.
  • ATTRITION - Rocks being carried by the river smash together and break into smaller, smoother and rounder particles.
  • SOLUTION - Soluble particles are dissolved into the river.

 

Transport

Rivers pick up and carry material as they flow downstream.

 

The four different river transport processes:

  • SOLUTION - Minerals are dissolved in the water and carried along in solution.
  • SUSPENSION - Fine light material is carried along in the water.
  • SALTATION - Small pebbles and stones are bounced along the river bed.
  • TRACTION - Large boulders and rocks are rolled along the river bed

 

gcsere6.jpg

 

Rivers need energy to transport material, and levels of energy change as the river moves from the source to mouth.

  • When energy levels are very high, large rocks and boulders can be transported. Energy levels are usually higher near a river's source, when its course is steep and its valley narrow. Energy levels rise even higher in times of flood.                            
  • When energy levels are low, only small particles can be transported (if any). Energy levels are lowest when velocity drops as a river enters a lake or sea (at the mouth).

 

Deposition

When a river loses energy, it will drop or deposit some of the material it is carrying.

  • Deposition may take place when a river enters an area of shallow water or when the volume of water decreases - for example, after a flood or during times of drought.
  • Deposition is common towards the end of a river's journey, at the mouth.
  • Deposition at the mouth of a river can form deltas - for example, the Mississippi Delta.

RIVER LANDSCAPES

A river flows from an upland source (e.g. mountains) to the mouth where it enters the sea.

The river channel widens as it flows from its course to the sea and the amount of water it carries (known as discharge) increases as other streams and rivers join it.

 

geomorpohology3.gif

 

 

 

 

 

 

 

 

 

 

 

 

 

MAKE SURE YOU KNOW WHAT ALL THESE KEY WORDS MEAN.

 

  • SOURCE - Where the stream begins: usually where there is a spring, and quite high up
  • V-SHAPE VALLEY - Are usually found in the mountains and hills. They often have very steep sides.
  • INTERLOCKING SPURS - As the river erodes the landscape in the upper course, it winds and bends to avoid areas of hard rock. This creates interlocking spurs, which look a bit like the interlocking parts of a zip.
  • TRIBUTARY - A stream or river that flows into and joins a main river.
  • CONFLUENCE - Where two rivers or streams meet.
  • MEANDER - A bend in a river - usually in the middle or lower course.
  • OX-BOW LAKE - A small arc-shaped lake formed when a meander is sealed off by deposition. Oxbows are only found on river floodplains.
  • RIVER CLIFF - Created on the outside of a meander bend by the erosive effect of fast-flowing water.
  • SLIP-OFF SLOPES - Forms on the inside of a meander bend as a result of deposition in the slower flowing water.
  • LEVEE - River embankments built by deposition as the river floods.
  • DELTA - A fan-shaped area of sediment built up at the mouth of a river.
  • ESTUARY - Occurs near or at the mouth of a river, where the tide meets the current and the fresh and salt waters mix.
  • WATERSHED - The highland separating one river basin from another.
  • MOUTH - The end of the river. The mouth may be where the river meets the sea, a lake or a larger waterway. Most rivers flow out into the sea, and this is where they end their journey.

 

 

rivercourse.jpg

 

 

 

 

DRAINAGE BASINS

The land based part of the hydrological cycle is called the Drainage Basin System. A drainage basin is the name given to the area of land which is drained by a river. When water reaches the surface there are a number of routes which it may take in its journey to reach the river

1-background-rivers.jpg

MEANDERS

 
A meander is a bend in a river. Meanders normally occur in the middle and lower courses where the water is moving more slowly. The river carves out 'S-shaped' bends.
 
Meanders are formed by erosion. As rivers move from source to mouth, they carry sediment and other material. Energy is needed to carry this sediment.
 
On the outside of a meander the water is deeper and the current flows faster. The force of the water erodes and undercuts the outside of the bend by corrasion, forming a steep cliff called a river cliff.
 
On the inside bend of a meander the water is flowing more slowly as it has less distance to travel. There is normally deposition on the inside bend. This is because the load is too heavy for the river to carry. Sand and mud are deposited on the inside bend.
 
 
 
meander.jpg
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 meander1.jpg
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
OX-BOW LAKES
 
An oxbow lake is a landform of river erosion. It forms when a river cuts through the outside bend of a meander and flows straight. The old meander loop is cut off and the lake is sealed by new deposits of silt.
(When the river floods it breaks through the thin meander neck and the river takes the easier, straight course.  This leaves the meander loop ‘cut off’ as an oxbow lake.)
 
 
ox-bow2.jpg
 
 
oxbow.jpg
 
 
 
 

WATERFALLS

Waterfalls form where the river bed has a layer of harder rock overlying the softer rocks.

  1. As water falls the softer rock is eroded much more quickly than the harder rock; therefore undercutting the harder rock.
  2. The hard, overrhanging rock eventurally collapses.
  3. The collapsed rocks fall into the plunge pool causing more erosion of the soft rocks and a deeper plunge pool.
  4. This goes on continuously causing the waterfall to retreat upstream.
  5. The waterfall leaves a steap sided gorge as it reatrets.

 

waterfall-formation23.png

 

 

 

 

 

 

 

 

 

 

 

TOURISM AT NIAGARA FALLS

Tourism at Niagara Falls is usually in the summertime, when Niagara Falls are both a daytime and evening attraction. From the Canadian side, floodlights illuminate both sides of the falls for several hours after dark (until midnight). Approximately 22 million people visit the falls each year.

 

lesson-6-niagara-falls-1.ppt lesson-6-niagara-falls-1.ppt

 

falls1.jpg

 

While tourism at Niagara Falls does create many jobs, and generates extra income for the city there are some negatives.

Streets that tourists would not drive down stay neglected, cracked and potholed, while streets in the tourism district have been repaved several times over.

Houses are constantly torn down to make way for bigger, taller hotels.

Chain restaurants move in and push family owned, historical restaurants out of business.

Increase of litter, noise and traffic.

FLOODING

A flood occurs when a river bursts its banks and the water spills onto the floodplain. Flooding tends to be caused by heavy rain: the faster the rainwater reaches the river channel, the more likely it is to flood. The nature of the landscape around a river will influence how quickly rainwater reaches the channel.

 

flooding.jpg

FLOODING - MEDC CASE STUDY - BOSCASTLE

On the 16th August 2004 the picturesque tourist village of Boscastle on the North Cornish coast experienced a devestating flash flood, later described by the Environment Agency as 'among the most extreme ever recorded in Britain'.

 

lesson-9-case-study-boscastle-flooding-1.ppt lesson-9-case-study-boscastle-flooding-1.ppt

lesson-9-flood-management-and-boscastle.ppt lesson-9-flood-management-and-boscastle.ppt

 

case-study-boscastle06-1.jpg

FLOODING - LEDC CASE - BANGLADESH

The land is densely populated. Most of the land forms a delta from three main rivers - Ganges, Brahmaputra and Meghna - and 25% of Bangladesh is less than 1m above sea level. Flooding is an annual event as the rivers burst their banks. Bangladesh also experiences many tropical cyclones. The low-lying land means it is easily flooded. The snowmelt in the Himalayas adds water into the main rivers. There are human causes too - building on the floodplains and cutting down trees both increase the effects of flooding.

lesson-10-bangladesh-floods.ppt lesson-10-bangladesh-floods.ppt

 

21-river-flooding-management-issues.jpg

 

bangladesh-flooding.jpg

 

 

 

 

 

 

 

 

 

 

 

MANAGEMENT OF FLOODING

Steps can be taken to manage flooding. Often these steps involve trying to lengthen the amount of time it takes for water to reach the river channel. Flood management techniques can be divided into hard and soft engineering options.

Hard engineering options tend to be more expensive and have a greater impact on the river and the surrounding landscape.

Soft engineering options are more natural and tend to be cheaper.

 

lesson-11-hard-and-soft-engineering-flooding.ppt lesson-11-hard-and-soft-engineering-flooding.ppt

Remember to consider the advantages and disadvantages of both hard and soft engineering.

HYDROGRAPHS

WHAT ARE HYDROGRAPHS? - The amount of water in a river at any given point and time is known as the discharge which is measured in cumecs (cubic metres per second). This can be calculated by multiplying river velocity by channel volume at a given point and time.

Hydrographs are graphs which show river discharge over a given period of time and show the response of a drainage basin and its river to a period of rainfall.

 

hydrographs-explained.ppt hydrographs-explained.ppt

 

flood-hydrograph.gif

6 FIGURE GRID REFERENCES

Make sure you know how to do both 4 figure and 6 figure grid references. In the exam they may give you a landform to locate and state the 4/6 figure grid reference in your answer, OR they may give you the 4/6 figure grid reference and you have to say what is there.

 

6-figure-grid-references.ppt 6-figure-grid-references.ppt

six-fig-grid-ref-practice.xls six-fig-grid-ref-practice.xls

 

 

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