Rivers Flashcards
what is the river like in the upper course?
steep v-shaped steep sides narrow shallow channel
what is the river like in the middle course?
medium gradient
gently sloping sides
wider
depper channel
what is the river like in the lower course?
low gradient very wide almost flat very wide deep channel
what are the 5 processes of erosion in a river?
- vertical and lateral erosion
- hydraulic action
- abrasion
- attrition
- solution
what does vertical erosion do the river?
- deepens river channel, V-shaped
- upper course
what does lateral erosion do to the river?
- widens Vally
- middle and lower course
what is hydraulic action?
force of water breaks down rocks away from river channel
what is abrasion?
- eroded rock scrape channel
- most erosion is abrasion
what is attrition?
- eroded rock smash into each other
- edges round off
what is solution?
-river water dissolves certain types of rock i.e. limestone
what is transportation?
movement of eroded material
what are the 4 main methods of transportation?
- traction
- saltation
- suspension
- solution
what is traction?
large particles push along river bed by water
what is saltation?
pebble sized bounce along river bed by water
what is suspension?
small particles like soil and clay carried in water
what is solution?
soluble material dissolved in water carried along
what are the 4 reasons a river deposits material?
- volume of water in river falls
- eroded material increases
- sallow water
- river reaches mouth
what are the 3 land formed formed from erosion?
- waterfalls and gorges
- interlocking spurs
how are waterfalls and gorges formed?
- river flows over hard rock which is over soft rock
- soft rock eroded by hydraulic action and abrasion
- step formed
- water flows over step erodes more soft rock
- steep drop formed, WATERFALL
- hard rock undercut, collapse
- rock erodes at base by abrasion
- more undercutting, collapse
- waterfall retreats, GORGE
how are interlocking spurs formed?
- upper course river erode vertically
- v-shaped valleys
- not powerful enough to erode laterally
- wind around high hillsides
- leaving interlocking spurs
what are the landforms formed form erosion and deposition?
meanders and ox-bow lakes
how are meanders formed?
- current faster on outside bend
- more erosion on outside, forming river cliffs
- current slower as its shallower on inside
- so eroded lateral deposited
- this formed slip off slopes
how are ox-bow lakes formed?
- erosion in a meander, outside bend closer
- small neck
- breaks through, flood
- river goes shortest course
- deposition cuts off meander
- ox-bow lake left
how are the landforms formed from deposition?
- levées
- flood plains
- estuaries
how are flood plains formed?
- wide valley floor
- prone to flooding
- flooded deposition occurs on floodplain
- builds up floodplain
- meanders get wider making it bigger
how are levées formed?
- natural embankment
- flood, eroded material deposits on floodplain
- heaviest closest to river
- over time creates levées
how are estuaries formed?
- where river meets sea
- mouth of river
- tidal (rises and falls each day)
- tide at high point, water moves slowly so deposition
- creates mudflats
- low tide, mudflats exposed
what are some of the major erosion and deposition landforms on the River Tees?
- High Force waterfall
- meanders at Dent Bank
- tight meander and floodplain at The Holmes
what are the 4 main physical factors which cause a river to flood?
- prolonged rainfall
- heavy rainfall
- geology (rock type)
- relief (change in height)
how does prolonged rainfall make a river flood?
- soil saturated
- rain can’t infiltrate
- high runoff
- flooding
how does heavy rainfall make a river flood?
- cant infiltrate, too quick
- high runoff
- discharge quickly
- flood
how does geology make a river flood?
- clay soils, granite
- impermeable, no infiltration
- high runoff
- discharge increases quickly
- flood
how does relief make a river flood?
- steep sided valley
- reach river quickly
- flows quickly
- discharge increases
- flood
what human factor makes a river flood?
land use
how does land use make a river flood?
- buildings are made of impermeable materials
- drives, tarmac
- trees intercept water, cutting down trees stops the interception
- disappearing gardens
what do hydrography show?
discharge at certain point changes over time in relation to rainfall
what is river discharge?
- volume of water flowing into river per sec.
- cumecs
what is peak discharge?
highest discharge
what is lag time?
delay between peak rainfall and peak discharge
what is rising limb?
increase in river discharge as rainwater flows into river
what is falling limb?
decrease in river discharge as river returns to normal level
why does lag time happen?
most water doesn’t land directly in the river
what are the 4 main hard engineering strategies?
- dams and reservoirs
- channel straightening
- embankments
- flood relief channels
what are the advantages and disadvantages of dams and reservoirs?
A- store lots of water
A- drinking water
A- hydroelectric power
D- expensive
what are the advantages and disadvantages of channel straightening?
A- moves out of area quickly
D- flooding downstream
D- erosion downstream, fast moving water
what are the 5 main soft engineering strategies?
- flood warnings
- preparation
- flood plain zoning
- planting trees
- river restoration
what is an example of a flood management scheme in the UK?
Jubilee river flood reel channel
why was the scheme required(Jubilee river)?
- low lying
- prone to flooding
- royal settlement (Windsor) attracts visitors
- Eton school
what measures were taken(Jubilee river)?
Jubilee river was created to take overflow water from the Thames during high discharge
what were the social issues(Jubilee river)?
-is it ethical to protect wealthier places over others
what were the economical issues(Jubilee river)?
- most expensive in the UK
- but damaged a year later by floods
- £330million
- until solution found small business couldn’t operate while flooded
what were the environmental issues(Jubilee river)?
- concrete weirs are ugly
- algae collecting behind weirs disrupting other habitats
