topic 4 - river landscape Flashcards
the upper course
gradient -
valley and channel shape
steep gradient
the valleys are steep-sided and shaped like a v
water flows through a narrow and shallow channel
In the upper course,
erosion
erosion dominates over the deposition
the middle course
gradient -
valley and channel shape-
medium gradient
valleys have a gentle slope
wider and deeper channel than the upper course
the lower course
gradient -
valley and channel shape
gentle gradient
very wide and flat valley sides
the channel is wide and deep
cross
profile
shows you what a cross-section of the river looks like.
long
profile
Shows you how the gradient of a river changes along its length.
Types of River Erosion
vertical erosion
lateral erosion
lateral erosion
lateral erosion makes the river valley wider
lateral erosion dominated in the middle and lower Course
vertical erosion
vertical erosion makes the river valley deeper
vertical erosion dominates the upper course
due to high turbulence causing the rough and angular particles to be scrapped along the river bed
processes of transportation
solution
traction
saltation
suspension
process of erosion
hydraulic action
abrasion
attrition
solution
solution
soluble material dissolved in the water and are carried along
suspension
small particles like slit and clay are carried along by the water
saltation
when small particles bounce along the river bed by the force of the water
traction
is where large panicles eg boulders are dragged along the river bed by the force of the water
disposition is when a river drops eroded material
4 reasons why rivers slow down and deposit material
the water becomes shallow
the river reaches the mouth
reduced volume of water in the channel
the number of sediments in the channel increases
what features are found in the upper course
waterfalls and gorges
formation of waterfall
as the river passes over bands of hard and soft rocks, the less resistant (soft) rocks begins to erode because of abrasion and hydraulic action.
as the softer rock is eroded away by the river a step or notch forms creating a river rapid
overtime the the softer rocks gets more eroded and a steep drop is eventually a waterfall forms
the hard rocks is eventually undercut by erosion and the overhanging harder rocks becomes unsupported and collapses
the hard rocks crumble into the base and abrasion between the hard rocks and soft rocks creates a plunge pool
hydraulic action keeps undercutting and causes more collapses
the waterfall will retreat leaving behind a steep-sided gorge
formation if interlocking spurs
in the upper course , valleys are steep and v-shaped because most erosion happens vertically downwards
and rivers are don’t have the energy to erode laterally Instead, they follow the winding path through the valley.
These interlocking hillsides are the interlocking spurs.
features in the lower and middle course
meanders
formation of meanders
meanders are large bends in a river.
when the river bends the current in the fastest at the outside of the bend so more erosion takes place on the outside of the bend forming a river cliff
the current is the slowest on the inside of the bend because the water is the shallowest so eroded material is deposit because the current has less energy to carry it along the river. This creates slip-off slopes.
formation of ox-bow lakes
Over time, meanders get bigger until eventually an ox-bow lake forms.
erosion causes the outside bends to get closer
until there’s only small bit of land left between the bends and eventually the river breaks through this land deposition eventually cuts off the meanders forming an ox bow lake
River Landforms Caused by Deposition
flood plains
levees
deltas
floodplains
flood plain are flat and wide areas of land that floods
Flood plains are created by meander migration close to the mouth of the river.
Meanders widen floodplains by migrating across them.
Meanders make valley floors flatter by migrating downstream.
levees
are natural embankments along the edge of a river channel
during a flood the eroded material is deposited. the heaviest material is deposited first closest to the river channel over time the deposited material build up on the sided of the river
deltas
deltas are low-lying areas where the river meets the sea or lake
deltas forms because the river are forced to slow down when they meet the sea or lake causing them to deposit their sediments
The river’s channel can be blocked by this build-up of material. This splits the river into lots of tiny rivers named distributaries.
If this material builds up enough, a piece of land called a delta is created.
factors Affecting River Landscape and Sediment Load
climate
geology
slope processes
factors Affecting River Landscape and Sediment Load- geology
rivers flowing through areas of hard rocks have a slower rate of erosion because hard rocks are more resistant so a river will have a lower sediment load.
landscape with more resistant rocks have steep-sided valleys
whereas areas of softer rocks will experience more erosion which adds material to the rivers sediment load.
landscape with less resistant rocks have gentle sloping valleys sides
factors Affecting River Landscape and Sediment Load- climate
rivers in wetter climate have a higher discharge because more water entering the river channel
higher discharge increases the rate of erosion
transportation also increases when there’s a high discharge
factors Affecting River Landscape and Sediment Load- slope processes
vertical erosion by rivers makes valleys more steeper and increases the movement of material down the slopes
what does the bar chart show on a hydrograph
rainfall
what does the line graph show
river discharge
What is river discharge measured in?
cubic meters per second m^3/s
what Affects the Shape of a Hydrograph?
physical factors
slope-A steeper valley will funnel more rainfall into a river faster, increasing river discharge.
geology - impermeable rocks will absorb less water and channel more rain into a river, increasing discharge (infiltration is lower).
soil type - Impermeable soils will have higher runoff and channel more water into a river.
drainage basin type
antecedent conditions
What Affects the Shape of a Hydrograph?
human factors
deforestation - cutting down trees means less water would be absorbed by the tress which increases discharge and runoff
urbanisation -Impermeable building materials are used for housing and buildings in urban areas. This will reduce infiltration and increase the discharge
How does flooding threaten the people?
Floodwater can easily get contaminated with sewage, leaving water unsafe to drink.
floods can wash people away and kill them.
Possessions can be destroyed or lost.
businesses and homes can be damaged.
How does flooding threaten the environment?
Habitats can be polluted by floodwater.
vegetation can be uprooted and killed by forceful floodwater.
the risk of flooding can increase due to
increase in the frequency of storms - this could be a consequence of global climate change
land-use change - lots of development eg houses taking place on floodplains .these areas are naturally prone to flooding
