Rivers

Rivers

Rivers as Systems
1. Evaporation
  1. Water droplets change to water vapour
2. Condensation
  1. Water vapour change to water droplets
3. Precipitation
  1. Movement of water from clouds to ground
4. Infiltration
  1. water from top of land through the soil
5. Interception
  1. Water lands on trees' leaves and branches
6. Surface Run-off
  1. Movement of water over ground
7. Through flow
  1. Sideways movement of water through the soil
8. Transpiration
  1. Leaves give water vapour into the air
9. Evapotranspiration
  1. Sum of Evaporation and Transpiration
Drainage Basins
1. Source
  1. Where a river begins
2. Confluence
  1. 2 Rivers meet
3. Tributary
  1. A stream flowing into a larger one
4. Watershed
  1. Edge of the drainage basin
5. Mouth
  1. River meets the sea
6. Estuary
  1. Part of the river thats tidal
7. Area of land drained by a river and its tributaries
River Processes
1. Abrasion
  1. Rocks carried by the river hit the bed and banks
2. Attrition
  1. Pebbles and rocks hit each other
3. Hydraulic Action
  1. Power of moving water hitting banks and forming cracks
4. Corrosion
  1. Acidic water dissolves rock
5. Traction
  1. Large rocks roll along the bed
6. Saltation
  1. Rocks bounce along the river beds
7. Solution
  1. Dissolved minerals
8. Suspension
  1. Small fragments float
River Features
1. Upper Course
  1. V-shaped Valleys
    1. Lateral Erosion
    2. Vertical erosion
    3. Precipitation
    4. Weathering of rock fragments
    5. Steeper slopes increase fall of sediment
  2. Interlocking Spurs
    1. Rivers wind around obstructions
  3. Waterfalls
    1. Bands of hard and soft rock
      1. Overhang
        Undercutting
    2. Plunge Pool
    3. Moves further upstream
  4. Gorge
    1. A valley creater by a waterfall eroding backwards
2. Lower Course
  1. Meanders
    1. Erosion
    2. Deposition
    3. Slowest current
    4. Inside bend
    5. Fastest current
    6. Outside bend
  2. Ox-box Lakes
    1. Continued erosion of the neck of a meander
    2. The river takes the straight course
    3. Deposition blocks off the old meander
  3. Estuaries
    1. TIdal areas where River meets the sea, slows down & deposits sand and mud = mudflats&salt marshes.
  4. Deltas
    1. Fan shaped areas of land where the river meets the sea, as the river slows down sand and mud get deposited
Flood Hydrographs
1. Shows amout of rainfall and water in the river
2. Peak Rainfall
  1. Hour of greatest rainfall during storm
3. Peak Discharge
  1. Time of maximum discharge by river
4. Base Flow
  1. Expected discharge of the time of year
5. Rising Limb
  1. Increasing discharge
    1. Rainfall finds it's way into the river
6. Falling Limb
  1. Decreasing discharge
    1. River carries storm rainfall away
7. Lag Time
  1. Time between:
    1. Highest rainfall
    2. Peak discharge
River Floods
1. Dams & Reservoirs (hard)
  1. Trap and store water
  2. Controlled release of downstream
  3. Expensive
  4. Generates Hydroelectricity, Displaces Communities, effective
2. Flood walls (hard)
  1. Concrete walls built around settlements
  2. Expensive, look artificial, may fail in extreme floods
3. Floodplain Zoning (soft)
  1. Can't build in flood risk areas
  2. Have things like football pitches instead
  3. Needs Careful planning
4. Flood prediction and warning (soft)
  1. Monitors river levels and rain
  2. Create flood risk maps
    1. Agency needed
5. Examples of River Floods
  1. Boscastle, England (2004)
    1. See a different mind map for more info
  2. Bangladesh (1998)
    1. See a different mind map for more into

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