Rivers

Rivers

1. Rivers as Systems

   • Evaporation
     • Water droplets change to water vapour
   • Condensation
     • Water vapour change to water droplets
   • Precipitation
     • Movement of water from clouds to ground
   • Infiltration
     • water from top of land through the soil
   • Interception
     • Water lands on trees' leaves and branches
   • Surface Run-off
     • Movement of water over ground
   • Through flow
     • Sideways movement of water through the soil
   • Transpiration
     • Leaves give water vapour into the air
   • Evapotranspiration
     • Sum of Evaporation and Transpiration

2. Drainage Basins

   • Source
     • Where a river begins
   • Confluence
     • 2 Rivers meet
   • Tributary
     • A stream flowing into a larger one
   • Watershed
     • Edge of the drainage basin
   • Mouth
     • River meets the sea
   • Estuary
     • Part of the river thats tidal
   • Area of land drained by a river and its tributaries

3. River Processes

   • Abrasion
     • Rocks carried by the river hit the bed and banks
   • Attrition
     • Pebbles and rocks hit each other
   • Hydraulic Action
     • Power of moving water hitting banks and forming cracks
   • Corrosion
     • Acidic water dissolves rock
   • Traction
     • Large rocks roll along the bed
   • Saltation
     • Rocks bounce along the river beds
   • Solution
     • Dissolved minerals
   • Suspension
     • Small fragments float

4. River Features

   • Upper Course
     • V-shaped Valleys
       • Lateral Erosion
       • Vertical erosion
       • Precipitation
       • Weathering of rock fragments
       • Steeper slopes increase fall of sediment
     • Interlocking Spurs
       • Rivers wind around obstructions
     • Waterfalls
       • Bands of hard and soft rock
         • Overhang
           • Undercutting
       • Plunge Pool
       • Moves further upstream
     • Gorge
       • A valley creater by a waterfall eroding backwards
   • Lower Course
     • Meanders
       • Erosion
       • Deposition
       • Slowest current
       • Inside bend
       • Fastest current
       • Outside bend
     • Ox-box Lakes
       • Continued erosion of the neck of a meander
       • The river takes the straight course
       • Deposition blocks off the old meander
     • Estuaries
       • TIdal areas where River meets the sea, slows down & deposits sand and mud = mudflats&salt marshes.
     • Deltas
       • Fan shaped areas of land where the river meets the sea, as the river slows down sand and mud get deposited

5. Flood Hydrographs

   • Shows amout of rainfall and water in the river
   • Peak Rainfall
     • Hour of greatest rainfall during storm
   • Peak Discharge
     • Time of maximum discharge by river
   • Base Flow
     • Expected discharge of the time of year
   • Rising Limb
     • Increasing discharge
       • Rainfall finds it's way into the river
   • Falling Limb
     • Decreasing discharge
       • River carries storm rainfall away
   • Lag Time
     • Time between:
       • Highest rainfall
       • Peak discharge

6. River Floods

   • Dams & Reservoirs (hard)
     • Trap and store water
     • Controlled release of downstream
     • Expensive
     • Generates Hydroelectricity, Displaces Communities, effective
   • Flood walls (hard)
     • Concrete walls built around settlements
     • Expensive, look artificial, may fail in extreme floods
   • Floodplain Zoning (soft)
     • Can't build in flood risk areas
     • Have things like football pitches instead
     • Needs Careful planning
   • Flood prediction and warning (soft)
     • Monitors river levels and rain
     • Create flood risk maps
       • Agency needed
   • Examples of River Floods
     • Boscastle, England (2004)
       • See a different mind map for more info
     • Bangladesh (1998)
       • See a different mind map for more into