Unit 2: 4- River Processes and pressures Flashcards
What is a course?
Path of the river as it flows down hill
Rivers form ____ and ____ as they flow downhill
Channles and vallys
How does tranportation happen in rivers
water erodes landscpae then transports the material somwher eles where it’s deposited
Why does the shape of the valley and channle chage along a river
it’s dpendant on weather erosion or deopstion is having the most dominatnt impact
What is a channle and valley?
What does the long profile and cross profile show you?
Long profile: How the gradient changes over diff courses
Cross profile: How the coss section of river looks
Desccribe the :Gardient vally shape,size and cross profile fot the upper middle and lower course
What is verticla and lateral erostion?
Verticla-> Deepens the valley + chanle making V-shaped. Dominant in upper course. High turbulances couse rough angular particles to scrape along the river bed causing intense downward erosiron
LAteral-> Widens the river valley + channel. During the formation o fmeanders. dominant in the middle an dlwer coureses
WHat is freeze-Thaw weathering? Descrie the procces of free-thaw wethering
=> it breaks down rock on the valley side type of mechanicla weathering
1. Happens when the temp alternates above and below 0
2. Water gets into a rcks crack e.g. granit. WHe water freezwz it expands wich put preassure on the rock. The water taws it contracts and realeaes prasur on the rock
3. Repeated freezeing and tawing causes rock to break
What aere th 4 types of erosion?
Hydraulic action the force of water brakes rock particles away form the river channele
Abrasion Eroded rocks picked up by the river scrpae and rub aginst the channle waering it awya most erostio happens by abrasion
Attrition Eroded rocks picked up byu river smash into each other and break into smaller fragemnts. their edges also get rounded off as the rub together . the further the material trvales the more eroded it gets trrition cuaes particle size to decres between rivers souruce and mouth.
Solution river dissolves some tyoes of rock e.g. chalk + limestine
What are the 4 processes of river transportation?
- Traction Large partiles like boulders arepushed along the river bed by the force of water
- Suspension Small particles like silt and clay are carried along by the water
- Saltation Pebble-sized particles bounce along river bed by force of water
- **Solution ** Soluable materials dissolve in the water and are carried along
WH
What is a waterfall? Describe the formation of waterfalls and gorges.
Waterfall-> Form where a river flows over an area of hard rock followed by an area of soft rock
1. Soft rock is eroded by Hydraulic action and arasion more than hard rock creating step in river
2. As more water goes over step= erodes more and more soft rock
3. A steep drop created = waterfall
4. Hard rock eventally undercut by erosion and collapese
5. Collaped rocks are swirled around at foot of waterfall where they erode softer rock by abrasion=> creates Plunge pool
6. Over time ore undercutting causes more collape the waterfall will retreat ( move back up channle) leaving behind steep sided gorge
What is deposition and why might it occur?
Deposition-> When river drops the eroded material it’s transporting .
* Happens whe river loses velocity
Reasons why river may slow down and lose velosity:
1. Vol of water in river falls
2. Amount of eroded materila in water increases
3. Water is shallower ( e.g. inside a bend)
4. River reaches it’s mouth
What are interlocking spurs? Where are they found/ WHta effect do they have on the landscape?
Interlocking spur->Hillsides that interlock with each other ( like a zip) as the river winds around them
* Usally in the upper course of the river
1. In upper course most erosion is verticla creating steep V-shaped valleys
2. Rivers arnt powerful enough to erode Laterally, therfore they mind around the high hillsides that stick out in theire path eather side.
Wher are waterfalls usally found?
Upper course of river
What is a Meander?Describe theire formation .
Meander->large bends in middle and lower course in areas there are both shalow and deep section of the channle
1. Current is faster in the outside of the bend because the river channle is deeper ( less friction to slow water down)
2. So more erosion ( Abrasion and Hydraulic action) takes place on outside of bend forming river cliffs.
3. The current is sloer on the inside of bend because the rievr channle is hallower ( more fiction to slow water down)
4. Eroded material depositted on the inside of bend forming Slip off slopes
Describe the formation of an Ox-bow lake.
- Erosion caues the ousde bend to get closer
- Until there is only a small bit of land left between bend= ‘neck’
- River breakes through this land usaully during flood
- River flow around shortest course
- Deposition evtually cut off meander
- Ox-bow lacke formed
What is a flood plain? What may be on it?
Flood plain-> I the wide valley floor on eaither side of a river wich occasionllay gets flooded
* When river floods the flood plain the water slows down and dposits eroede material that it’s transporting=> Builds up the flood plain
* Meanders migrate across the flood plain making it wider
* Meanders migrate downstream flattening out the valley floor
* The deposition that happens on slip off slopes kf meanders also builds up flood plain
What is a Delta? Why do they form?
Deltas-> Build of of material wich forms low lying areas
1. Rivers are forced to slow down when they meet a sea or lakce causin them to deposite the material tehy are carrying
2. If the sea dosn’t wash away the material it builds up and channle gets blcked
3.This forces the channel to split up into lots of smaller rivers and ditributarys
4. Eventually material builds up so much that low lying land is formed= Delta
Lable the digram
WHat are the factors effecting storm hydrogrphys?
Physicla
1. Geology
2.Soil type
3.Slope
4.Drainage + basin type
5.Antecendent conditions
Human
1.Urbanisation
2.deforestantion
Antecdent->pervous
