geog paper 1 gcse

• infiltration is the absorption and downward movement of precipitation in to the surface layers of soil
• percolation is the downward seeping of water through pores joints and other spaces in the soil and rock beneath the surface
• through-flow is the flow of water down a slope through the soil back to the river
• over land flow or surface run off is the downslope surface movement of water produced by sudden heavy precipitation
• transpiration is the loss of water vapour from plants
• ground water flow is the water contained within the soil or underlying rocks, water that has percolated through soil contributing to the saturated layer beneath the water table
• water table is the boundary, beneath the surface, between saturated and unsaturated ground
• stem flow is water running down a plant or trunk
• interception is the amount of water absorbed and used by plants
• abrasion is scraping, this is caused by material carried in the river rubbing against the bed and banks of the channel and wearing them away, abrasion causes the most erosion
• hydraulic action is the sheer force and pressure of the water hitting the river bed and banks, this form of erosion is important during high velocity, it causes mini explosions
• solutions is when river water is slightly acidi so it can dissolve some rocks and minerals in contact with the river. limestone and chalk most affected
• attrition is sediment particles carried in the river colliding with each other causing the edges to be knocked off. the continued collision of particles in the river causes them to become more round and small downstream
• suspension is the water carrying silt and clay sized particles. most common near mouth
• traction is stones rolled along the river bed most common near source
• solution is the transport of dissolved chemicals. this varies along the river depending on presence of soluble rocks
• saltation is the pebbles bouncing along the river bed, most common near source
• 1. shaped valleys

  Valleys formed when a river erodes vertically downwards
• Formation of v-shaped valleys

  1. Valleys sides are slowly broken down through weathering

  2. River discharge is low in upper course, so river only has enough energy to erode downwards (vertical erosion)

  3. Vertical erosion happens by abrasion, where material carried in river rubs against bed and wears it away

  4. This creates a deeper river channel and the start of a v-shaped valley

  5. Weathered material is transported via gravity and rainfall towards river channel, steepening valley sides

  6. As river continues to erode vertically, it exposes sides to freeze-thaw weathering, where water freezes in cracks causing sediment to fall away and steepening sides

  7. Steep-sided and narrow valley shape is typical of upland rivers
• Formation of a waterfall

  1. Waterfall occurs in the upper stages of a river

  2. Hard igneous rock (windstone) overlies soft sedimentary rock (limestone)

  3. Water and rock particles fall, eroding the soft rock below to create a plunge pool

  4. Soft rock is undercut by hydraulic action and abrasion, creating a plunge pool

  5. Water and debris swirl around, eroding the rock and deepening the plunge pool

  6. Hard rock overhang collapses into the plunge pool as it's no longer supported

  7. Erosion continues and retreats upstream, creating a gorge
• The river bends in its middle course each sharp bend is called meander. meanders are natural.

  • river almost never flow in straight line.
  • water flows naturally in Cork screw pattern- this is called Helicoidal flow
  • helicoidal flow sends rivers energy laterally ( to the side)
  • the fastest current is the thalweg
  • thalweg is forced to the out end where undercutting occours
  • a steep edge is created
• the river is trying to get to equilibrium
• how meanders form

  • the current is faster on the outer bend because the river is deeper
  • so more erosion takes place on the outer river bend creating river cliffs
  • current is slowed on the inside because the river channel is shallower
  • so eroded material is deposited on the inside bends creating slip off slopes
• meanders get larger over time to eventually create ox bow lakes
• formation of an ox bow lake

  • erosion causes the outside bends to become closer
  • until there is only a small bit of land left between the bends
  • the river breaks through this land usually during a flood
  • the river flows along the shortest corse
  • deposition eventually cuts off the meander
  • forming the ox bow lake
• inputs of a drainage system is precipitation and sediment
• throughputs of a drainage system is water stored in lakes ponds and aquifer or stored in ground water
• outputs of a drainage system is rivers seas and lakes and sediment dissolved in suspended bedload
• in upper course of the river

  • gradient is steep with v shaped valleys and interlocking spurs
  • width is narrow
  • depth is shallow
  • sediment is angular and jagged boulders with large clast size
  • the velocity is at its slowest although it appears choppy
• in the in the middle course of the river

  • the gradient is gradually getting flatter and river begins the flow through v shaped valleys
  • width is getting wider
  • depth is increasing as river has more erosive power and tributaries allow more water into channel
  • erosive power will reduce sediment size
  • river velocity will increase with more tributaries
• in the rivers lower course

  • the gradient is flat
  • the width is wide
  • depth is at its deepest as river discharge is at its highest therefore more erosive power
  • the sediment is smaller and smoother due to erosion
  • river is at its fastest
• causes of flooding

  • rains; inception, stem flow, infiltration, percolation
  • surface run off: the river rises quickly in cities because of no drainage in soil and impermeable ground, just goes down drain back to river again
• effects of flooding

  • social; schools close, driving with hazard lights on, homes ruined, people die, no electricity
  • economic; property prices fall, loss of income for farmers, train links down
  • environmental; drinking water in short supply, livestock gone missing
• somerset flooding case study

  • causes
  • jet stream changes- high level winds and low pressure bring heavy rain
  • man made levees- they raise the river bed further as the river bed naturally adjusts to new artificial banks
  • changes in agriculture
  • most rainfall since 1766- 235% above average
  • no higher than 8m above sea levels
  • high tides and tidal surges
  • loose material that had originally been dredged clogged the channel
• somerset flooding case study

  effects

  • social; business go bankrupt, food+farm products can’t be made because of floods
  • economic; business go bankrupt due to aftermath of flooding, loss of livelihood and income
  • environmental;90% of 300 acres of land constantly underwater, water can’t soak into soil leading to surface runoff back to river
• what factor makes the flood in somerset so severe ?

  lowest lying area of the uk, 8m above sea level

  increase in rainfall by 235% above average,

  not able to drain water so water has nowhere to go but to flood town
• storm hydrographs are used to assess and predict the risk of river flooding
• hydrograph is flashy it will flood

  it has a short lag time so it will flood
• if a hydrograph is subdued it won’t flood as there’s a long lag time
• When the river loses energy, it drops any of the material it has been carrying. This is known as deposition.

  Factors leading to deposition:

  • shallow water
  • at the end of the river's journey, at the river's mouth
  • when the volume of the water decreases