8 River Action Flashcards
Source
Place where a river begins
High ground
Tributary
Stren or river that joins a larger one
Confluence
The junction wheree two rivers join
Mouth
Place where a river enters sea or lake
Estuary
found at mouth of river where rivers current and seas tide meet
Drainage basin
Entire area of land drained by a river and its tributaries
Watershed
Area of high ground that separates one basin from another
Course
Distance river reacels from source to mouth
Fluvial
refers to processes associated with rivers and streams and the deposits and landforks created bt them
5 Typess of river drainage patterns
Dendritic
Trellis
Radial
Parallel
Deranged
What does a dendritic pattern look like
Branches of a tree
Random
Upland areas
What does a trellis drainage pattern look like
Ladder
Right angled confluences
Found where folding had occured
What does a radial drainage pattern look likke
Spokes of a wheel
Rivers run off a mountin or conical hill
Radiate from peak outwards
What does a parallel drainage pattern look like
rivers flow parallel
Run across valleys
What does a deranged drainage pattern look like
Streams have no particular direction
Lowland areas subjected to glacial deposition
What are the 4 Proccesses of river erosion
1.Hydraulic action
2.Abrasion/Corrasion
3.Attrition
4.Solution/Corrosion
factors that affect rate of river erosion
1.Vol of water
(Rivers in flood erode faster as theyve
more energy)
2.Speed/Velocity
(Erode faster when flow faster)
(this is affected by gradient and water
perimeter)
3.Hardness of rock
(Softer rocks are eroded easier)
What is hydraulic action
River bed +bank is eroded by force of moving water. Loose fragments swept away
Joints of rocks englarged
What is abrasion/corrasion
Material picked up by moving river erodes bed and bank of river
What is attrition
Rocks nd pebbles rub against eachother as theyre moved by river.
Makes them smoother and smaller
Solution/Corrosion
Soluble rocks in river channel are dissolved by acids in water
E.g Limestone dissolved by carbonic acid
4 Processes of river transportation
1.Solution
2.Suspension
3.Saltation
4.Traction
What is solution (transportation)
Dissolved rocks are carried in a solution
(Requires least energy)
What is suspension
light materials (sand,clay) r carried by moving water as a suspendded load.
common in times of flood when water is brown
What is saltation
Small light rocks/penbles are bounced along riverbed
What is traction
Heavy materials are rolled dragged along riverbbed
(Requires most energy)
When does a river depostit its load
1.Volume decreasss
(dry season, floods recede, water taken for agri use,)
2.Speed decreases
(enters a sea, increase in roughness)
What is the wetted perimeter of a river
The area of the riverbed and bank that comes into contact with water
PART THATS WET
Another name for youthful stage of a river
Upper valley
Characteristics of upper valley/youthful stage
Upland area
few tributaries
Small vol of water
Steep gradient
Quick flow
Vertical erosion
Landforms of youthful stage/upper valley
V shaped valley
Interlocking spurs
Waterfalls
What are eddy currents
Swirling action of water
usually occurs as water enters a hole
Formation of V Shaped Valley
1.Vertical erosion. Water uses energy to erode downwards
2. Weathering. Rivers on high ground so valley is weathered by freeze thaw
3.Mass Movement. Loose material travels down into valley
4.V Shaped Valley. Steep Sided narrow valley is formed
What is differential erosion
Less resistand rocks are worn down at a faster rate than more resistant rocks
Eg. Chalk is worn down quicker than granite
Interlocking spurs formation
Youthful stage
River
