•the forms of river valleys as a long profile and a cross profile
•the long profile is from the side-on view and the cross profile is from head on
•the shape of the valley
•upper section: •a narrow v shaped valley; a narrow channel; the river will fill the floor
•will be full of large boulders; turbulent waters
•rough channel; flowing slowly; dominated by vertical erosion
•traction and saltation
•hydraulic action, attrition and abrasion
•middle section: •channel is deeper and wider; broken ‘u’ shape
•lots of deposits; lateral erosion; smaller load
•discharge increase; velocity increase
•suspension
•lower section: •very wide valley and larger channel; often floodplain
•full of smaller rocks; sand sized; smoother channel
•faster flowing river; lateral erosion
•the formation of waterfalls
•1. a layer of more resistant rock is exposed across the bed of a river channel
•2. differential erosion occurs, the more resistant rock is undercut by softer rock underneath
•3. the harder rock collapses into it’s plunge pool due to the abrasion and hydraulic action
•the process is repeated
•4. the repeat results the waterfall retreating back up it’s valley, it leaves a narrow, steep sided valley below the waterfall called a gorge
•this results in the waterfall becoming smaller leaving a steeping section which just produces rapids
•the formation of potholes
•1. a weakness or crack or fault line is exposed
•2. differential erosion takes place, as abrasion and hydraulic action erodes the fault
•3. this produces a pothole
•4. the potholes enlarge until they begin to merge with one another
•5. eventually, the whole river bed is lowered due to vertical erosion of abrasion and action
•the formation of meanders
•the bends on rivers are called meanders
•they are formed by erosion on the outer bend and deposition on the inner bend as water flows fastest on the outside due to less friction and more depth
•the river cliff is repeatedly undercut by erosion and collapses and has large sediment size whilst the slip off slope is shallower with smaller sediment size and alluvium
•the formation of oxbow lakes
•1. the meander will develop and enlarge as the outside bank erodes
•2. the neck becomes narrower and eventually breaks, usually from floods due to energy
•3. the oxbow lake becomes slower, increasing deposition and the meander is cut off during high flow
•4. the oxbow lake is sealed off by deposition on both sides of the channel and the oxbow lake evaporates, leaving behind a scar
•the formation of deltas
•when a river enters a large body of water, the remaining load will be deposited at it’s mouth and if there are no tidal currents to the beach, the deposits will form deltas on low flat land
•the deposition of small sediment causes the fine clay to stick together and gain weight, dropping to the sea bed
•the heavier bedlam material drops first, producing fore-set beds and the lighter suspended material is carrie further away from the coast, forming bottom-set beds
•on top of the delta the channel may split into several distributaries
•it’s bed fills with alluvium and partly blocks the channel so that the water flows around the blockage, spreading across the delta
•the growth of vegetation on the delta will help trap more sediment an raise the delta above sea level
•since it leads to a sea or a lake, the delta has a reduced velocity
the formation of levees
•levees are formed when a river floods because as the water overflows the channel, it slows
down therefore more of the load, and a coarser part is deposited close to the channel,
making the banks higher
•during normal flows, the river deposits on the bed, making it higher than the plain
•the formation of floodplains
•the meander erodes sideways as it travels downstream
•when the river overflows, it deposits alluvium
•the build up of this flooding creates the floor of the floodplain
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