Studied by 10 people
steep gradient
V-shaped valley, steep sides, narrow, shallow channel
medium gradient
gently sloping valley sides, wider, deeper channel
gentle gradient
very wide, almost flat valley, very wide, deep channel
deepens valley, V-shaped
dominant in upper course
high turbulence causes intense downward erosion
widens valley + channel during meander formation
dominant in lower + middle course
volume of water falls
eroded material increases
water is shallower (e.g. inside of bend)
river reaches its mouth
velocity of water
size of particles
forms over an area of hard rock then soft rock below
softer rock erodes by H.A and abrasion more than the hard rock, creating a 'step' in the river
water flows over step eroding more of softer rock
steep drop is created, called the waterfall (e.g. High Force waterfall on the River Tees, County Durham)
hard rock undercut by erosion, unsupported + collapses
collapsed rock swirls around foot of waterfall where they erode softer rock by abrasion creating deep plunge pool
undercutting causes more collapses, waterfall retreats leaving a steep-sided gorge
faster current on outside bend as river channel is deeper
erosion takes place on outside bend, forming river cliffs
slower current on inside bend as river is shallower
deposited eroded material in inside bend, forming slip-off slopes
erosion causes outside bends to get closer until narrow neck is created
flooding makes river breaks through neck
river flows along the shortest course, through neck
deposition cuts of meander forming ox-bow lake
e.g. River Calder, near Castleford, West Yorkshire
during floods, water slows down + loses energy and deposits transported material building floodplain
meanders widen as they move across floodplains laterally
over time, meanders move downstream
during floods, eroded material deposited over flood plain
heaviest material deposited closest to the river channel as it gets dropped first when the river slows down and loses energy
gradually, deposited material builds up, creating levees along edges of channel
e.g. River Trent, Nottinghamshire
water floods over river banks carrying silt + sand on valley floor
tide reaches highest point and waves moves slowly with little energy depositing sediment
mud builds up creating large mudflats
at low tide, wide + muddy banks are exposed
They are the orange lines over a map; they tell you:
height of land (in metres) by the numbers marked on them
steepness of the land by how close together they are (closer the lines= steeper slope)
waterfalls are marked on maps but the symbol for cliffs are black, blocky lines and the close contour lines are evidence for an upper course waterfall
the height gives it away
river crosses a lot of contour lines in a short distance showing it's steep
the river is narrow (thin blue line)
nearby land is low
river doesn't cross any contour lines so it's gently sloping
river meanders across a large flat area
rivers wide (thick blue line)
river has large meanders + ox-bow lake may have formed
surface runoff (flows quickly overland)
infiltration (soaks into ground and runs underground)
heavy rainfall
geology (rock type)
prolonged rainfall
relief (changes in land height)
land use
buildings and roads are made from impermeable materials increasing surface runoff; man-made drains transport runoff to rivers increasing discharge
cutting down trees increases the volume of water that enters the river channel as trees intercept water on their leaves which evaporates
dams and reservoirs
channel straightening
embankments
flood relief channels
flood warnings + preparation
flood plain zoning
planting trees
river restoration
What are they?
dams are barriers built across the river, usually in the upper course + a reservoir is formed behind the dam
Benefits
stores water (e.g. after heavy rain) controlling water flow preventing flooding downstream
generates HEP
Cons
expensive to build
farmland downstream becomes less fertile as material is deposited in the dam
What is it?
meanders are removed by building straighter + artificial channels
Benefits
water leaves area quicker rather than building up, lowers flood risk
Cons
flooding may happen downstream instead
faster-moving water may cause more erosion downstream
What are they?
raised walls built along river banks
Benefits
river holds more water lowering flooding
Cons
expensive
risk of flooding if water flows above embankments
What are they?
channels built to divert water around built-up areas or to divert excess water if river level gets to high
Benefits
gates control water release
Cons
increased discharge where the relief channel rejoins the river which could cause flooding in that area
What are they?
E.A issues flood warnings through various media/buildings are modified to minimise flood damage/residents can prepare sand bags and flood boards prior to floods
Benefits
give people time to move possessions upstairs
evacuation
Cons
warnings don't prevent floods
modifying buildings is expensive
What is it?
restrictions prevent building on part of a flood plain that are likely to be affected by floods
Benefits
reduced flood risk, less impermeable surfaces
no buildings to damage
Cons
expansion of an urban area is difficult is there isn't any other suitable building sites
can't help in areas with existing buildings
What is it?
planting trees in river valleys increases interception of rainwater + lag time
Benefits
discharge and flood risk decrease
vegetation reduces soil erosion in valleys providing habitats for wildlife
Cons
less land available for farming
What is it?
making the river more natural
Benefits
improves wildlife habitats
little maintenance
Cons
local flood risk can increase, especially if nothing is done to prevent major flooding
