river proccesses Flashcards
Transportation of rocks(suspension)
tiny particles of sediment
Transportation of rocks(solution)
dissolved chemicals being carried
Transportation of rocks(salutation)
smaller stones picked up and dropped again
Transportation of rocks(traction)
large stones dragged across
Erosion of the river bed(abrasion)
sand and pebbles dragged along the river wearing away the bed
Erosion of the river bed(attrition)
rocks and stones wear each other as they knock together
Erosion of the river bed(hydraulic action)
fast flowing water is forced into cracks
Erosion of the river bed(solution)
alkaline are dissolved
How water falls work
1) a bed of more resistant rock
2) erosion of less resistant rock by abrasion and hydraulic action
3) the rivers energy causes a plunge pool underneth
4) This creates a ledge that collapses
5) takes up new position leaving a gorge
Features of the upper course
steep and narrow forming a v shaped valley, produces interlocking spurs which jut into the river valley
weathering(biological)
small crack allow plant to grow and the roots push it apart
weathering(physical)
physical force breaks rock like freeze thaw
weathering(chemical)
chemical change
mass movement
all process that cause rock material to move down slope
mass movement(rapid)
landslides and mud flow fast flowing
mass movement(slow)
soil creep caused by rain dislodging tiny soil particles
shape of the valley is effected by
rate of weathering, mass movement and how quickly the river removes material
Features of the middle course
gradient is gentler, discharge has increases(volume of water), Velocity increases due to smaller rocks, meanders, point bars, u shaped valley
meanders how they are created
1) water flows in a helicodial flow
2) fastest current called the thalweg is forced to the outer bend
3) this creates a river cliff
4) helicodial flow shifts sediment to the other side here it is deposited to create a point bar
5) as river channel shifts it forms a flood plain
lower course features
wide and deep, flat gradient, discharge is larger, low lying flood plain
the channel of the lower course(how its made)
twice a day the incoming tide meets the outgoing tide and forces the river to stop depositing sediment
this forms a wide area called mudflats, some rivers drop so much it forms a delta
natural levees
as a river reaches bankful it deposits sand and clay forming a natural barrier.
artificial levees
built by engineers
long profile
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