Geography-Water on the land

Rivers
1. Upper Course
  1. Steep
  2. V-shaped
  3. Narrow
  4. Shallow
2. Middle Course
  1. Medium steepness
  2. Gently sloping sides
  3. Wider
  4. Deeper
3. Lower Course
  1. Gentle
  2. Very Wide
  3. Almost flat
  4. Deep channel
Erosion, Transportation and Deposition
1. Erosion
  1. Hydraulic Action
    1. Force of water breaks down rock particles from the river channel
  2. Abrasion
    1. Eroded rocks picked up by the river scrape and rub against the channel, wearing it away. Most erosion happens by abrasion
  3. Attrition
    1. Eroded rocks picked up by the river smash into each other and break into smaller fragments. Their edges also get rounded off as they rub together.
  4. Solution
    1. River water dissolves some type of rock, e.g. chalk or limestone.
2. Transportation
  1. Traction
    1. Large particles , like boulders, are pushed along the river bed by the force of water.
  2. Saltation
    1. Pebble-sized particles are bounced along the river bed by the force of water.
  3. Suspension
    1. Small particles, like silt and clay, are carried along by the river.
  4. Solution
    1. Soluble materials dissolve in the water and are carried along.
3. Deposition
  1. When a river drops the eroded material.
    1. Happens when the river slows down (loses velocity).
      1. 4 reasons as to why a river loses velocity.
        Volume of water decreases.
        Amount of eroded material increases.
        The water is shallower.
        The river reaches its mouth.
River Landforms
1. Meanders
  1. Middle or lower course
  2. 1. The current is faster on the outside of the bend because the water is deeper.
  3. 2. More erosion takes place on the outside of the bend, forming river cliffs.
  4. 3. The current is slower on the inside of the bend because its shallower.
  5. 4. So eroded material is deposited on the inside of the bend, forming slip-off slopes.
2. Ox-Bow Lakes
  1. Formed form large meanders.
  2. 1. Erosion causes the outside bends to get closer..
  3. 2...until there's only a small bit of land left between the bends (called the neck).
  4. 3. The river breaks through this land, usually during a flood..
  5. 4..and the river flows along the shortest course.
  6. 5. Deposition eventually cuts off the meander...
  7. 6..forming an ox-bow lake.
3. Waterfalls and Gorges
  1. 1. Waterfalls form where a river flows over an area of hard rock followed by an area of softer rock.
  2. 2. The softer rock is eroded more than the hard rock, creating a 'step' in the river.
  3. 3. As water goes over the step it erodes more and more of the softer rock.
  4. 4. A steep drop is eventually created, which is called a waterfall.
  5. 5. The hard rock is eventually undercut by erosion. It becomes unsupported and collapses.
  6. 6. The collapsed rocks are swirled around at the foot of the waterfall where they erode the softer rock by ABRASION. This creates a deep plunge pool.
  7. 7. Over time, more undercutting causes collapses. The waterfall will retreat, leaving behind a steep-sided gorge.
4. Flood Plains and Levees.
  1. Flood plain
    1. 1. This is the wide valley floor on either side of a river which sometimes floods.
    2. 2. When a river floods onto the flood plain, the water slows down and deposits the eroded material. This makes the flood plain higher.
    3. 3. Meanders migrate across the flood plain, making it wider.
    4. 4. The deposition that happens on the slip-off slopes of meanders also builds up the flood plain.
  2. Levees
    1. 1.These are natural embankments (raised bits) along the edges of a river channel.
    2. 2. During a flood, eroded material is deposited over the whole flood plain.
    3. 3. The heaviest material is deposited closest to the river channel, because it gets dropped first when the river slows down.
    4. 4. Over time, the deposited material builds up, creating levees along the edges of the channel, e.g. along the Yellow River in China.
Rivers on maps
1. Contour lines
  1. Orange lines on maps.
  2. Height = number marked on.
  3. Steepness = how close together they are.
2. Evidence for a waterfall
  1. They are marked on a map, but the symbol for a cliff is black, blocky lines.
River Discharge
1. Volume of water that flows in a river per second. Measured in CUMECS (m^3/s)
2. Peak discharge = The highest discharge in the period of time you're looking at.
3. Lag time = The delay between peak rainfall and peak discharge.
4. Rising limb = The increase in river discharge as rainwater flows into the river
5. Falling limb = The decrease in river discharge as the river returns to its normal level.
6. What affects river discharge?
  1. Amount and type of rainfall
    1. Lots of rain and short, heavy periods of rainfall means there's more RUNOFF. Lag time is decreased, so discharge increases.
  2. Temperature
    1. Hot, dry conditions and cold, freezing conditions both result in hard ground - this increases RUNOFF. Lag time is decreased, so discharge increases.
  3. Previous weather conditions
    1. After lots of rain, soil can become saturated (absorbs more water). More rainwater wont be able to INFILTRATE into the soil so RUNOFF will increase. Lag time is decreased and discharge increases.
  4. Land use
    1. Urban areas have drainage systems and they're covered with impermeable materials like concrete - these increase RUNOFF. Lag time is decreased and discharge is increased.
  5. Rock type
    1. Water INFILTRATES through pore spaces in permeable rock and flows along cracks in previous rock - this means there isn't much RUNOFF. Lag time is increased, so discharge decreases.
    2. Water can't INFILTRATE into impermeable rock - this means there's a lot of RUNOFF. Lag time is decreased, so discharge increases.
  6. Relief
    1. Lots of RUNOFF occurs on steep slopes. Lag time is decreased, so discharge increases.
7. Lag time happens because most rainwater doesn't land directly in the river channel - there's a delay as rainwater gets to the channel. it gets there by flowing quickly overland (called SURFACE RUNOFF or just RUNOFF), or by soaking into the ground (called INFILTRATION) and flowing slowly underground.
Flooding
1. Physical Factors
  1. Prolonged rainfall
    1. After a long period of rain, the soil becomes SATURATED. Any further rainfall can't INFILTRATE, which increases RUNOFF. This increases discharge quickly, which can cause a flood.
  2. Heavy rainfall
    1. Heavy rainfall means there's a lot of RUNOFF. This increases discharge quickly, which can cause a flood.
  3. Snowmelt
    1. When a lot of snow or ice melts it means that a lot of water goes into a river in a short period of time. This increases discharge quickly, which can cause a flood.
  4. Relief
    1. If a river is in a steep-sided valley, water will reach the river channel much faster because water flows more quickly on steep slopes. This increases discharge, which can cause a flood.
2. Human factors
  1. Deforestation
    1. Trees intercept rainwater in their leaves, which then evaporates. Trees also take up water from the ground and stores it. This means cutting down trees increases the volume of water that reaches the river channel, which increases discharge and makes a flood more likely.
  2. Building construction
    1. Buildings are often made from impermeable materials, e.g. concrete, and they're surrounded by roads made from tarmac (also impermeable). Impermeable surfaces increase RUNOFF and drains quickly runoff to rivers. This increases discharge, which can cause a flood.
3. Case studies
  1. Carlisle, England. 8th January 2005. River Eden
    1. Causes
      1. 200mm of rain in 36 hours.
      2. Impermeable materials increased RUNOFF.
      3. Discharge reached 1520 CUMECS.
    2. Primary effects
      1. 3 deaths.
      2. 3000 people left homeless.
      3. 4 schools flooded.
      4. 350 businesses shut down.
      5. 70000 addresses lost power.
      6. Roads and bridges damaged.
      7. Rivers polluted.
    3. Secondary Effects
      1. Children lost out on education.
      2. Stress-related illnesses.
      3. 3000 jobs at risk.
    4. Immediate responses
      1. People evacuated.
      2. Reception centres - food and water.
      3. Temporary Accomodation.
    5. Long-term responses
      1. Emotional support.
      2. Flood defence scheme.
  2. Bangladesh, India. July-August 2007. River Brahmaputra and Ganges.
    1. Causes
      1. 900mm in July.
      2. Melting snow from Himalayas.
      3. Peak discharge happened at same time.
    2. Primary effects
      1. 2000 deaths.
      2. 25 million homeless.
      3. 44 schools destroyed.
      4. Livestock killed.
      5. 112 000 houses destroyed.
    3. Secondary effects
      1. Kids lost out on education.
      2. 100 000 caught water-borne disease.
      3. flooded fields reduced basmati rice yields.
      4. Unemployment rose.
    4. Immediate responses
      1. International charities provided food and water. And also boats.
      2. Many did not evacuate.
    5. Long-term responses.
      1. International charities funded rebuilding of homes.
      2. Homes rebuilt on stilts, so they're less likely to be damaged in the future.
Hard Vs soft engineering
1. Hard engineering
  1. Man-made structures built to control the flow of rivers and reduce flooding.
  2. Dams and reservoirs
    1. Dams (huge walls) are built across the rivers, usually in the upper course. A reservoir (artificial lake) is formed behind the dam.
      1. Benefits
        Reservoirs store water, especially during periods of prolonged rainfall, which reduces chance of flooding.
        Can be used as drinking water and for hydroelectric power.
      2. Disadvantages
        Eroded material is deposited in the reservoir and not along the river,so farmland downstream can be less fertile.
  3. Channel straightening
    1. The river's course is straightened - meanders are cut out by building artificial straight channels.
      1. Benefits
        Water moves out of the area more quickly because it doesnt travel as far - reducing risk of flooding
      2. Disadvantages
        Flooding may happen downstream.
        More erosion downstream.
2. Soft engineering
  1. Schemes set up using knowledge of a river and its processes to reduce the effects of flooding.
  2. Flood warnings
    1. The environment agency warns people about possible floods through tv, radio etc.
      1. Benefits
        The impact of flooding is reduced - warnings give people time to evacuate.
      2. Disadvantages
        Warnings dont stop a flood.
        Difficult to get insured.
        May not be heard.
  3. Preparation
    1. Buildings are modified to reduce the amount of damage.
      1. Benefits
        Impact of flooding is reduced. Buildings are less damaged.
      2. Disadvantages
        Doesnt guarantee safety. False sense of security. Its expensive.
  4. Flood plain zoning
    1. Restrictions prevent building on parts of a flood plain.
      1. Benefits
        Risk of flood reduced - impermeable surfaces aren't created.
      2. Disadvantages
        Expansion is limited.
  5. 'Do nothing'
    1. No money is spent on engineering methods.
      1. Benefits
        Farmland is more fertile.
      2. Disadvantages
        Risk of flood isnt reduced. A flood will cause a lot of damage.
Managing the UK's water
1. Demand
  1. The north and west of the UK have high rainfall, which means there's a good supply of water.
  2. The south and east have high population densities, which means they have a high demand for water.
  3. The south east and south are areas of water deficit (there's a greater demand than water.)
  4. The north and west are areas of water surplus (greater supply than demand).
2. Management
  1. Transfer water from a surplus to a deficit.
    1. e.g. Wales - Birmingham.
    2. Expensive.
    3. Affects Wildlife.
    4. political issues.
  2. Deficits to build more reservoirs.
    1. But can cause flooding and relocation of local people.
3. Reduce demands
  1. Reduce amount of water you use.
  2. Install water meters.
UK reservoir- case study.
1. Rutland Water - East Midlands.
  1. Built-1970's.
  2. 12km^2 area.
  3. River Welland & River Nene.
  4. Supplies water for Peterborough.
  5. Impacts
    1. Economic
      1. Boosts local economy.
      2. Popular tourist attraction.
        Wildlife
      3. 6km^2 of land was flooded to create it.
        Farmers lost livllihoods.
    2. Environmental
      1. Wildlife is protected.
      2. 10,000 waterfowl come at winter.
      3. Variety of habitats.
      4. Ospreys have been reintroduced.
      5. Large area was flooded,destroying habitats.
    3. Social
      1. Recreational activities.
        Sailing, cycling, birdwatching
      2. Jobs been created.
      3. Educational visits.
      4. Two villages were demolished.

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