Geography- Water on the Land

• The path a river flows downhill is called its course
• Rivers have an upper course (closest to source) a middle course and a lower course (closest to mouth)
• rivers form channels and valleys as they flow downhill
• They erode the landscape- wear it down, then transport the material to somewhere else where its deposited
• The shape of the valley and channel changes along the river depending on whether erosion or deposition is having the most impact (dominant process)
• The long profile of a river shows you how the gradient changes through the course
• The cross profile shows you what the cross section of river looks like

Upper- Steep- vertical erosion

• V-shaped valley, interlocking spurs, steep sides, narrow, shallow channel

Middle- Medium- lateral erosion

• Gently sloping valley sides, wider, deeper channel- ox-bow lakes

Lower- Gentle- lateral erosion

• very wide, almost flat valley, very wide, deep channel- deltas

Both types happen at the same time but one is usually more dominant

Vertical erosion:

• Deepens the river valley (and channel) making it v-shaped, it is dominant in the upper course of the river

Lateral erosion:

• This widens the river valley (and channel), it is dominant in the middle and lower course of the river

Hydraulic Action:

• The force of the water breaks rock particles away from the river channel

Abrasion:

• Eroded rocks picked up by the river scrape and rub against the channel, wearing it away. most erosion happens by abrasion

Attrition:

• Eroded rocks picked up by the river smash into each other and break into smaller fragments, their edges get rounded off as they rub together

Solution:

• River water dissolves some types of rock e.g. chalk and limestone

Porous:

• Rocks with pore spaces between the grains which allow it to absorb water
• e.g. chalk

Permeable:

• Rocks with cracks and spaces that allow water to pass through
• e.g. limestone

The eroded material is transported downstream by the 4 processes:

Traction: Large particles like boulders are pushed along the river bed by the force of the water (roll along)

Saltation: Pebble sized particles are bounced along the river bed, they are picked up and dropped as the flow of the river changes

Suspension: small particles like silt and clay are carried along by the water giving the river a brown appearance

Solution: soluble materials like limestone and chalk are dissolved in the water and carried along in the flow

Deposition is when the river drops the eroded material it is transporting

It happens when the river slows down (loses velocity)

There are a few reasons why rivers slow down and deposit material:

• The volume of water in the river falls
• the amount of eroded material in water increases
• the water is shallower e.g. on inside of bend
• the river reaches its mouth

Formed by erosion and deposition- found in middle and lower course, lots of meanders in the Mississippi river USA

1. The current is faster on the outside of the bend because the river is deeper and there is less friction to slow the water down

2. More erosion takes place on the outside of the bends forming river cliffs

3. The current is slower on the inside of the bend because the river channel is shallower so there is more friction to slow the water down

4. eroded material is deposited on the inside of the bend, forming slip off slopes

(draw picture)

Ox-Bow lakes are formed from meanders e.g. Connecticut

1. erosion causes outside bends to get closer

2. erode until only a small bit of land between the bends (the neck)

3. the river breaks through, sometimes causing a flood

4. the river flows along the shortest route

5. deposition cuts off the meander, forming and ox-bow lake

(draw diagrams)

Waterfalls (e.g. High Force waterfall on the river tees) form where a river flows over an area of hard rock followed by softer rock

1.the softer rock is eroded more than the harder rock- creating a 'step' in the river

2. as the water goes up the step it erodes more and more of the softer rock

3. a deep drop is created- waterfall

4. the hard rock is eventually undercut by erosion, becomes unsupported and collapses

5. the collapsed rocks are swirled around at the foot of the waterfall where they erode the softer rock by abrasion, creating a deep plunge pool

6. over time, more undercutting causes more collapses the waterfall will retreat leaving behind a steep sided gorge (e.g. cheddar gorge)

A waterfall is formed usually in the upper course of a rivers journey to the see, where there are horizontal bands of hard and soft rock. The overlying hard rock is eroded slower than the softer rock through hydraulic action and abrasion. An overhang is formed which eventually collapses as the weight of the overlying cap rock is too great, creating the steep drop of the waterfall. The eroded material will erode the back wall and sides creating a large plunge pool through the processes of attrition. Over time these processes of undercutting and collapse is repeated many times, causing the waterfall to retreat upstream, creating a gorge, Niagara falls, in Canada has been formed in this manner, where the hard limestone rock overlies softer shales and sandstone on the Niagara river.

The flood plain is formed by deposition, found in the lower course of the river e.g.River earn

• it is the wide valley floor on either side of a river which occasionally gets flooded
• when a river floods onto the flood plain, the water slows down and deposits the eroded material that it's transporting, this builds up the flood plain making it higher
• meanders migrate (move) across the flood plain making it wider
• the deposition that happens on the slip-off slopes of meanders also builds up the flood plain

These are natural embankments along the edges of a river channel- found in lower course and caused by deposition

• during a flood eroded material is deposited over the whole flood plain
• the heaviest material is deposited closest to the river channel because it gets dropped first when the river slows down
• over time the deposited material builds up creating levees along the edges of the channel
• e.g. along the Yellow river in China

Contour lines are the orange lines on maps

they tell you the height of land (by numbers) and the steepness of the land (by how close the lines are together)

V-shaped valleys form where the contour lines cross the river

Upper course:

• land is high (note how many metres)
• the river will cross a lot of contour lines in a short distance which means its steep
• river will be narrow (thin blue line)
• the contour lines will be very close together and the valley floor narrow means the river is in a steep-sided v-shaped valley
• evidence for a waterfall: marked on, but evidence is symbol for a cliff (black, blocky lines) and close contour lines

Lower Course

• nearby land is low (number)
• only crosses like 1 contour line- very gently sloping
• evidence=river joining sea or lake
• river is wide (thick blue line)
• has meanders across flat area with no contours (flood plain)
• has large meanders

=volume of water flowing in a river per second, measured in cumecs (m3/s)

hydrographs show how the discharge at a certain point in a river changes over time

storm hydrographs show the changes in river discharge around the time of a storm

peak discharge= the highest discharge in the period you are looking at

lag time= the delay between peak rainfall and peak discharge

rising limb= the increase in river discharge as rainwater flows into the river

falling limb= the decrease in river discharge as it returns to normal level

lag time happens because most rainwater doesn't land directly in the river channel- delayed as rainwater gets to the channel, its gets there by flowing quickly over land (surface runoff) or by soaking into the ground (infiltration) and flowing slowly underground

The more water that flows as run off, the shorter the lag time, this means the discharge will increase as more water gets to the channel in a shorter space of time

Amount and type of rainfall:

• lots of rain and short, heavy periods of rainfall means there's more run off, lag time decreased so discharge increased

Previous weather conditions:

• after lots of rain soil can become more saturated, more rainwater won't be able to infiltrate into the soil so runoff will increase, lag time decreased, discharge increased

Land Use

• urban areas have drainage systems and they're covered with impermeable materials like concrete, increase runoff, lag time decreased, discharge increases

Temperature:

• Hot, dry conditions and cold freezing conditions both result in hard ground- increases runoff, lag time decreased, so discharge increases

Rock type:

• water infiltrates through pore spaces in permeable rock and flows along the cracks in pervious rocks- isn't much run off so lag time increases and discharge decreased
• water can't infiltrate through impermeable rock- a lot of run off, lag time decreased and discharge increased

Relief:

• Lots of run off occurs on steep slopes, lag time decreased, discharge increased

flash floods= flood happening without warning

The river channel increases when discharge increases because a high discharge means that there is more water in the channel, this means factors that increase discharge can cause flooding:

Prolonged rain:

• after a long period of rain, the soil becomes saturated, any further rainfall doesn't infiltrate which increases runoff into rivers. this increases discharge quickly, which can cause a flood

Heavy rain:

• heavy rain means there is a lot of runoff, increases discharge quickly which can cause a flood

Snowmelt:

• When a lot of snow or ice melts it means that a lot of water goes into a river in a short space of time, this increases discharge quickly which can cause a flood

Relief:

• If a river is in a steep-sided valley water will reach the river channel much faster because water flows more quickly on steeper slopes, increases discharge quickly which can cause a flood

Deforestation:

• trees intercept rainwater on their leaves which evaporates. trees also take up water from the ground and store it. so cutting down trees increases the volume of water that reaches the river channel, it increases discharge and makes flooding more likely

Building construction:

• Buildings are often made from impermeable materials e.g. concrete, and they're surrounded by roads made from tarmac (also impermeable). impermeable surfaces led rainwater underground into drains and straight into rivers leaving little chance for evaporation into the atmosphere. discharge increases quickly which can cause a flood

16th August 2004

90mm of rain fell in 1 hour

at 3.30pm river valency burst its banks

was a flash flood- no warning

6cm of rain fell in 2 hours- 3m high wall of water went through the village

rain happened quickly so could not be absorbed

coastal winds gave extra omph

• Boscastle is where the river valency and River Jordan meet
• water fall near by shows steepness of land
• only small woodland
• houses built on flood plain- concrete so water can't soak in
• no warning about flood- usually to have floods in august
• never had flood so weren't prepared

Primary:

• Roads were blocked- emergency access was difficult except from air
• property destroyed by debris- entire trees and vehicles
• people were trapped- seek refuge on roofs, danger of hypothermia and being swept away
• people were left homeless- emergency accommodation set up
• people left without cars so were unable to return home
• burst sewage main damaged buildings and made inaccessible for health reasons

Secondary:

• damage to properties had to be repaired- time consuming and costly
• home insurance in boscastle more expensive
• loss of tourist attractions- loss of revenue, may never recover tourist industry fully

Immediate:

• emergency services responded speedily and efficiently
• helicopters airlifted people to safety
• first stage of the clean up was inspection and securing buildings
• infrastructural damage of roads, sewers and electricity, gas and water supplies repaired

Long term:

• £800,000 spent on flood defence scheme completed in boscastle by April 2005
• engineers investigating future flood control on the river

River Ganges and river Brahmaputra run into Bangladesh

very fertile soil

Bangladesh= populous county of 150million people

in September 2004, Dhaka had its worse rainfall for 50 years

Bangladesh= one of worlds poorest countries

Physical:

• most of country is a flood plain and delta of the River Ganges and Brahmaputra
• 70% of total area is less than 1m above sea level
• Rivers, lakes and swamps cover 10% of land
• heavy monsoon rain in summer- in Dhaka almost 2000mm
• tropical cyclones from the bay of Bengal bring heavy rain and storms
• snow melts in Himalayas makes Ganges flood

Human:

• population grown rapidly- removal of forest to provide fuel, timber and grazing
• forests- absorb water from the ground and bind soil particles together to reduce impact of rain, removal of forest cover- increased soil and overland flow, soil deposited in river channels causing bed to rise, reduces capacity of river
• the building of farakka dam in India blamed for rising of the River Hooghly's bed

Primary:

• floods covered over half of Bangladesh
• 760 killed
• 35 million affected
• 8.5 million left homeless
• rice and fish farming disrupted
• roads and bridges destroyed

Secondary:

• more than 1million children suffered from malnutrition and disease
• government rebuilding costs= US $2-3 billion
• emergency aid was needed until following years harvest

Immediate:

• concern for health, survival and suffering of those affected
• heavy reliance of emergency aid- food, water, plastic sheets
• problem of distribution of water purification tablets- so much of the country underwater once began to recede became easier and helped provide help rebuilding and repairing damage and economy

Long term:

• In July 1987 world bank prepared plan for flood control that involved making 3500km of coastal and river embankments and 7 dams- stop water from reaching land and provide 15 floodwater storage basins
• people suggested flood forecasting systems- more flood shelters stocked with emergency supplies
  • cheaper and more appropriate for farming and fishing communities, also less like to damage delicate ecosystem.

Hard engineering=  man-made structures built to control the flow of rivers and reduce flooding

Soft engineering- schemes set up using knowledge of a river and its processes to reduce affects of flooding

Dams and reservoirs:

• dams are built across river in the upper course, a reservoir is formed behind
• reservoirs store water especially during prolonged periods of heavy rain
• water is used for drinking and for Hydro-electric power
• are very expensive
• can flood existing settlements
• eroded material is deposited in the reservoir not along rivers course so farms further down stream become less fertile

Channel straightening:

• rivers course is straightened- meanders cut out
• water moves out of area more quickly because doesn't travel as far
• flooding may happen downstream as water is carried there faster
• more erosion downstream as water is faster

Flood warnings

• the environment agency warns people early on TV, radio, newspapers, internet
• impact of flooding reduced as people can move possessions upstairs, put out sandbags and be ready to evacuate
• don't stop flood happening, some people may not hear about warnings
• could become difficult to get insurance

Preparation:

• buildings modified to reduce damage a flood could cause, plans made, keep important things like blankets and torches at hand
• impact flooding reduced- buildings modified, people know what to do, worry less
• doesn't guarantee safety from a flood, could give false sense of security
• expensive to modify homes 

Flood plain zoning

• restrictions prevent building on flood plains
• risk is reduced- less impermeable surfaces, less impact as aren't house or roads to be damaged
• expansion of urban area is limited if there aren't any other suitable sites
• no help in areas that have already been built on

'Do Nothing':

• no money spent on new engineering methods or maintaining existing ones
• flooding is a natural process and people should accept the risks of where they live
• the river floods, eroded material is deposited, farmland more likely to be fertile
• risk of flooding and impacts aren't reduced
• flood will cause a lot of damage

rises in the Pennines where precipitation is high, rocks permeable, slopes steep, its a flashy river and has history of flooding, managed to control flooding and protect tourism

Upper course: cow green reservoir, built in 1970 to provide water for industries, traps heavy rainfall and water from snowmelt, allows water flow regulation

Lower Course- Yarm's flood defence- serious flood January 1995, £2.1 million spent

• reinforced concrete walls and metal flood gates
• earth embankments and gabions
• fishing platforms, street lighting and replanting- improve environment
• building materials approved by English heritage

near the tidal mouth- river straightening, dredging and the Tees barrage

• 1810 meander cut off- shortening river, aid navigation
• dredged to maintain deep water
• 1995 Tees Barrage completed, £5.4 million to maintain high water levels and reduce flood risk

The places with good supply of water aren't the places with the highest demand

• In the north and west there is the highest rainfall- good supply of water
• south east and Midlands have high population densities- higher demand for water
• south east and Midlands are areas of water deficit(greater demand than supply)
• North and west are areas of water surplus (great supply than demand)

demand for water increasing:

• over the past 25 years the amount of water used by people in the UK has gone up by about 50%
• the UK population is predicted to increase by around 10million people over the next 20 years

one way to deal with supply demand problems is to transfer water from areas of surplus to areas of deficit e.g. Birmingham (deficit) is supplied with water from the middle of Wales (surplus)

Water transfer can cause issues:

• dams and aqueducts are expensive
• could affect wildlife that lives in the area e.g. fish migration patterns would be affected by dam building
• might be political issues- people may not want to give their water to other countries

could increase water supplies in deficit areas by building more reservoirs to store more water- can involve flooding settlements and relocating people

Fixing leaky pipes could mean less water is lost in transfer- e.g. millions of litres of water is lost in London every day from leaking pipes

• can reduce the amount of water use at home
  • have showers, only run washing machines when full, use hosepipe less
• water companies want people to have water meters installed- charge people for the exact volume of water they are using so people are more likely to be more careful about the amount of water they use

Facts and Figures

Kielder water= over 10km long

largest artificial lake in the UK

planned in late 1990's to satisfy increased demand for water- opened in 1982

The north tyne valley has a large relatively large floor with steep sides

annual precipitation is high- 1370mm

few people lived in the valley- only a few families needed to be moved and rehoused

the land was mainly poor quality farmland remote from markets

limited variety of lost wildlife habitats in an area of rough grazing and coniferous woodland

Notes:

• water is transferred to the populated parts of the north east
• water is released directly into the River North Tyne from river Tyne at riding mill its pumped through a tunnel then its fed into other east flowing rivers

Derwent reservoir: primary source of water- water from kielder is used to supplement the river supplement flow when its low

North-east- most reliable and sustainable water supply in england

• restrictions on water e.g. hose pipe bans are unknown even in driest areas e.g. 1995 when lake district reservoirs dried up

drought in Yorkshire in 1995

• building 13km pipeline link south from river Tees to the Ouse river system in York

Economy benefited:

• water and land based leisure activities attract over a quarter of a million visitors each year
• kielder forest= largest woodland in England
  • attracts lots of different species and wildlife, e.g. red squirrel
• jobs in water industry, tourism and forestry- previously only farming

highest dam in Africa

disadvantages:

• farmland lost- loss of independence for small farmers
• small gardens and fruit trees lost- compensate will a 'food parcel'
• longer walk to school for the children because valley flooded

benefits:

• water for Johannesburg (city without a river)- industry, water gardens, drinking
• water sold for money- £36 million a year
• jobs created in Lesotho- civil engineering means become more skilled
• HEP plant

dam built in Rutland water, east Midlands in the 1970's

The reservoir covers a 12km2 area and it's filled with water from 2 rivers- River Wellend and River Nene

Rutland water was designed to supply the east Midlands with more water- enough to cope with rapid population growth in places like Peterborough

Areas around the reservoir are used as a nature reserve and for recreation

Economic:

• reservoir boosts local economy- popular tourist attraction because of wildlife and recreation facilities
• Around 6km2 of land was flooded to create the reservoir- included farmland so farmers lost their livelihoods

Social:

• lots of recreational activities take place on and around the reservoir e.g. sailing, windsurfing, birdwatching and cycling
• many jobs have been created to build and maintain the reservoir, and to run the nature reserve and recreational activities
• schools use the reservoir for educational visits
• 2 villages were demolished to make way for the reservoir

Environmental:

• Rutland water is a Site of Special Scientific Interest (SSSI) an area where wildlife is protected
• Hundreds of species of birds live around the reservoir and tens of thousands of waterfowl come to Rutland water in the winter
• A variety of habitats are found e.g. marshes, mudflats and lagoons- lots of different organisms live in or around
• Ospreys (birds that were extinct in Britain) have been reintroduced to central England by the Rutland Osprey Projects at the reservoir
• a large area was flooded to create the reservoir so some habitats were destroyed

• supply of water must be sustainable- means that people will be able to get water today without stopping people in the future having enough water
• people can't deplete the water supply or damage the environment too much
• people can only take out as much water as is replaced by the rivers that supply it- so it stays the same for the future