Geography - River Environments

• Hydrological cycle


  A closed system, therefore it has no inputs and outputs, only transfers and stores
• Stores in the hydrological cycle

  • Atmosphere
  • Surface stores (puddles, lakes, rivers, reservoirs)
  • Aquifers
  • Ice and snow
  • Seas and oceans
• Transfers in the hydrological cycle

  • Evaporation
  • Condensation
  • Transpiration
  • Evapotranspiration
  • Precipitation
  • Overland flow
  • Infiltration
  • Percolation
  • Through & groundwater flow
• Drainage basin


  An open system
• Features common to all drainage basins

  • Watershed
  • Source
  • Confluence
  • Tributary
  • Mouth
• Drainage density


  The number of tributaries in a drainage basin
• Impermeable rock or soil

  Leads to high drainage density because the water cannot infiltrate, therefore the water flows over the surface in tributaries
• Permeable rock or soil


  Leads to low drainage density because water can infiltrate
• River regime


  A record of changes in river discharge over the period of a year
• Storm hydrograph


  Shows the changes in river discharge after a storm event
• Features of a storm hydrograph

  • Base flow
  • Peak rainfall
  • Rising limb
  • Peak discharge
  • Lag time
  • Recessional limb
• Factors affecting river discharge/regime

  • Climate
  • Vegetation
  • Land use
  • Geology
  • Soils
  • Abstraction
  • Dams
  • Relief
  • Drainage density
• Fluvial processes


  Processes that shape the river and surrounding land in the drainage basin
• Landscape processes


  • Weathering (physical/mechanical, chemical, biological)
  • Mass movement (slumping, soil creep)
• Fluvial erosion processes


  • Hydraulic action
  • Abrasion
  • Attrition
  • Corrosion/Solution
• Fluvial transportation processes


  • Traction
  • Saltation
  • Suspension
  • Solution
• Deposition


  When the sediment that a river is transporting is dropped
• Long profile of a river

  Shows the changes in the river gradient from the source to the mouth
• Characteristics of the upper, middle and lower course of a river

  • Upper course: Shallow channel, Steep valley sides, Narrow channel, Low velocity, Large bedload, Rough channel bed, High levels of friction, Vertical erosion
  • Middle course: Deeper than upper course channel, Gentle valley sides, Wider than upper course channel, Greater velocity than upper course channel, Material in river decreases in size, Smoother channel bed, Lower levels of friction than upper course channel, Lateral erosion
  • Lower course: Deeper than middle course channel, Flat floodplains, Wider than middle course channel, Greater velocity than middle course channel (apart from as the river enters the mouth), Material carried mainly sediment and alluvium, Smooth channel bed, Lowest friction, Deposition is dominant
• Cross profile of a river

  Cross-sections from one bank to another
• The upland and lowland areas of rivers have distinctive landforms
• Upland river landforms


  • Waterfalls
  • Gorges
  • V-shaped Valleys
  • Interlocking Spurs
• Formation of waterfalls and gorges


  1. Less resistant (softer) rock begins to erode because of abrasion and hydraulic action

  2. More resistant (harder) rock remains, forming a waterfall

  3. Over time, the waterfall retreats, forming a gorge
• Case study: River Tees
• Lower course characteristics

  • Deeper than middle course channel
  • Flat floodplains
  • Wider than middle course channel
  • Greater velocity than middle course channel (apart from as the river enters the mouth)
  • Material carried mainly sediment and alluvium
  • Smooth channel bed
  • Lowest friction
  • Deposition is dominant
• Lateral erosion


  Erosion of the river banks
• Lower course has less friction than upper course channel
• River Tees


  • Location: North-East England
  • Drainage basin - 1830km2
  • Source - Cross Fell, Pennines 754m above sea level
  • Length - 137 km
  • Mouth - Tees Estuary, North Sea
  • Direction of flow - West to East
• The changes in river channel characteristics, lead to changes in the river landscape
• Upland river landforms


  • Waterfalls
  • Gorges
  • V-shaped Valleys
  • Interlocking Spurs
• Formation of waterfalls and gorges

  1. Stage 1 - the less resistant (softer) rock begins to erode because of abrasion and hydraulic action, a step or notch forms in the softer rock, creating a river rapid

  2. Stage 2 - over time, the softer rock gets more eroded, this leaves the hard rock sticking out above the soft rock

  3. Stage 3 - the less resistant rock starts to be eroded underneath the hard rock, this process is called undercutting; the overhanging harder rock collapses because there is nothing underneath it to support it and the hard rock crumbles into the base and the abrasion between the hard rock and soft rock base creates a plunge pool; then hydraulic action keeps undercutting behind the waterfall (if the process repeats over a long time, a gorge may form)
• 1. shaped valleys


  Vertical erosion is dominant in the upper course of the river, cutting down into the river bed and deepening the river channel, weathering and mass movement leads to material from the valley sides collapsing into the river forming a steep v-shaped valley
• Interlocking spurs


  In the upper course, valleys are steep and V-shaped because most erosion happens vertically downwards, the rivers do not have a lot of energy as there is not a lot of fast-moving water, this lack of energy means that they do not erode sideways (lateral erosion), instead, they follow the winding path through the valley, these interlocking hillsides are the interlocking spurs
• Meanders


  Formed in the middle course of a river: as the river gains more velocity, the water is pushed to the outside of the river causing more erosion on the outside bend, which forms a steep river cliff; this is achieved through processes like hydraulic action and abrasion
• Ox-bow lakes


  Formed by continual erosion and deposition narrows the neck of the meander, often during a flood the river will cut through the neck, the river continues on its straighter path and the meander is abandoned, new deposition seals off the ends and the cut-off becomes an oxbow lake that will eventually dry up
• Floodplains


  Formed by migration of meanders leads to the formation of the floodplain, high discharge may cause the river to overflow the banks, more of the water is in contact with the land surface as the water spreads across the floodplain, increased friction reduces velocity and material is deposited across the floodplain gradually increasing the floodplain height
• Levees


  Formed naturally during floods, water overflows over the banks of a river, the larger sediments that were being transported by the river will be deposited first, after lots of floods, levees (which are natural piles of sediment) are created at the side of the river
• 2.5% of the water on Earth is freshwater, 68.7% of freshwater is stored in glaciers and ice sheets and 30% is groundwater, 1.3% of freshwater is in rivers, soil moisture, lakes and the atmosphere
• Global water use by sector

  • 70% agriculture - irrigation of crops and water for livestock
  • 20% industry - producing goods and generating energy
  • 10% domestic - toilets, cooking, cleaning, washing
• Water demand


  The amount of water requested by users to meet their needs