rivers: keywords

• abrasion

  form of erosion where loose material, pebbles & sediment 'sandpaper' the walls & floors of a river
• attrition

  rocks hit against each other until they chip away into sediments
• biological weathering

  roots of plants break down rocks
• base flow

  normal flow of a river
• channelisation

  deepening or widening the river channel; lets water to flow more quickly away from areas at risk of flooding
• chemical weathering

  weak acid in rainwater dissolved chemical compounds in rocks
• confluence


  the point at which two rivers meet
• corrosion / abrasion

  river load is thrown against the river bed causing it to wear away the soil in the channel
• corrosion / solution

  weak chemicals in water break down rocks carried by river
• dam

  structure built to control the flow of a river & its discharge
• drainage basin

  area of land drained by a river system
• dredging

  aka catchment area_ area of land where all water flow & drain off into a sea
• erosion

  wearing away of rocks
• embankments

  banks of a river raised up by brick to increase channel capacity & prevent flooding
• flood plain zoning

  local authorities introduce policies to control development close to floodplains
• flooding

  water rises above river banks & flows onto the floodplain
• floodplain

  land next to a river ill be covered in water when the river bursts its banks
• floodplains are found in the LOWER COURSE of a river & act as overspill when the river channel is full
• freeze thaw

  form of physical weathering where water freezes in cracks, expands & enlarges crack
• geology

  physical structure & arrangement of a rock
• hard engineering

  making large scale changes to a river; often expensive changes that work against nature & involve changing the river banks
• hydraulic action

  pressure of compressed air forced into cracks of a rock face causes the rock to weaken & break apart
• interlocking spurs

  features of v shaped valley; formed as river winds its way downstream around resistant rocks
• lag time

  difference between PEAK rainfall & PEAK discharge (shows how fast water reaches the channel)
• levee

  flood bank that prevents a river from flooding
• long profile

  how gradient changes from SOURCE to MOUTH
• lower course

  channel is WIDE & DEEP; where VELOCITY is greatest & FRICTION least_ main river process= DEPOSITION
• lowlands

  area of land w/ small relief
• mass movement

  material move down a slope due to the pull of GRAVITY
• meander

  bend in the river channel caused by EROSION & DEPOSITION
• mechanical weathering

  breakdown of rocks due to forces (eg freeze thaw), not chemical reactions
• middle course

  river is deeper & has more power to erode
• metamorphic

  rock formed under intense pressure & heat, often due to tectonic plate movements
• permeable

  rock that allows water to pass through
• relief


  difference of height of land for a specific region
• ox bow lake

  river bend turns CUT OFF overtime due to deposition
• point bar

  water moves slowly on the inside of a meander bend & the river deposits some of its load, forming a point bar
• reservoir

  large body of water that builds up behind a dam
• river banks

  sides of the river channel
• river bed

  bottom of river channel