River landscapes and processes

what is the source of a river?

start of the river which any water flows down

what is the catchment area of a river?

the boundary of the drainage basin

what is a tributary in a river?

small river that contributes to the main channel

what is a confluence in a river?

a place where two river meet

what is the main river channel?

the main body of the river

what is the river mouth?

where the river ends, or where it joins another river or meets the sea

what is a long profile?

shows the gradient of a river through the entire length, it can be split into upper, middle and lower course

what is the cross profile of a river?

cross section taken sideways of a river channel at different points in the rivers course

what are the characteristics of the upper course?

• shallow

• steep gradient

• narrow

• low discharge

• velocity is low due to fiction agains the river channel sides

• carrries large angular stones

• vertical erosion occurs

what are characteristics of the middle course?

• wider river

• deeper

• gently sloping valley

• discharge increases as more streams join the river

• river flows faster as river is wider so less friction

• smaller and rounder sediment

• lateral erosion occurs as well as abrasion and hydraulic action

what are the characteristics of the lower course?

• widest

• deepest

• gently sloping valleys

• high velocity as there is very little faction from the channels sides

• large discharge as other rivers join together

• material carried by river is fine

• lateral erosion, deposition and erosion occurs

why do discharge and velocity increase downstream?

as river moves downstream, its discharge increases as more tributaries join the river. If the river us deeper there will be less contact between river and river ben therefore less friction will occur and velocity will be greater

how does climate affect river landscapes?

• rivers with wetter climates have higher discharge as there is more water entering the channel

• rates of erosion increases with discharge were the river has more energy to erode the river bed, this leads to more vertical erosion in the upper course, forming v shaped valleys

• and more lateral erosion in the lower course forming flood plains

• velocity also increases with discharge. As energy increases so does the rivers capacity to transport material.

how do storms affect river landscapes?

• storms bring increases rainfall causing the ground to be saturated, this can lead to mass movement on valley sides such as slumping, which can result in material entering the river channel.

• heavy rainfall also leads to more run-off causing volume of water in channel to increase, this means more transportation and erosion by abrasion and hydraulic action in upper course

• flooding causes the lower course of the river can lead to the formation of floodplains and levees

how do droughts affect river landscapes?

drought slow the flow of water in a river, which leads to less transportation and erosion and mass movement is less likely to occur

which landforms are created in the upper course?

interlocking spurs, waterfalls and gorges

what are interlocking spurs and how are they formed?

the hills that interlock with each other as the river winds around them are interlocking spurs, since the river doesn’t have enough energy to erode laterally the river winds around the hillsides, forming interlocking spurs

what is a waterfall and how is it formed?

• waterfalls are formed when a river flows over an area of hard rock followed by an area of softer rock.

• the softer rock is eroded faster than the harder rock by hydraulic action and abrasion

• this creates a step in the river

• as water goes over the step it erodes further

• a steep drop is eventually greater, called a waterfall

what are gorges and how are they formed?

• after a waterfall is created the harder rock is eventually undercut by erosion.

• it becomes unsupported and collapses

• the collapsed rocks are swirled around the foot of the waterfall where they erode the soft rock by abrasion

• this creates a plunge pool

• overtime more undercutting causes more collapses s the waterfall will retreat, leaving behind a steep-sided gorge

which river landforms are found in the middle course of the river?

meanders and oxbow lakes

what are meanders and how are they formed?

a meander is a large bend in a river

• the current is faster on the outside bend because the river channel is deeper so there is less friction to slow the water down

• so on the outside, erosion occurs due to high energy, e.g abrasion and hydraulic action

• overtime this forms a river cliff

• the inside bend has less energy as the current is slower because the river is shallower so there is more friction to slow the water down

• in the inside bend material is deposited

• overtime material deposited forms a point bar

what river landforms are found in the lower course?

floodplains and levees

what are floodplains and how are they formed?

flood plain is a wide valley floor on either side of a river which occasionally gets flooded

• when a river floods onto the flood play, the water slows down and deposits the eroded materials, this builds up the flood plain to make it higher

what are levees and how are they formed?

levees are natural embankments at the edges of a river channel

• during a flood eroded material is deposited over the whole flood plain

• the heaviest materials is deposited closest to the river channel as it gets dropped first when the river slows down

• overtime the deposited materials builds up, creating levees over edge of channel

how does urbanisation and industry affect river landscapes?

• the increasing building of roads and drains means that water can reach the river faster after rainfall, this means river is much more likely to flood due to disruption to the balance of water flow to the river

• this means defences are built to protect peoples homes, which further disrupts natural processes

how does agriculture after river landscaped?

• many tress have been felled to make sway for farming land, which interferes with infiltration and has an impact on flooding.

• fewer trees means water will reach river faster as there is less interception, which affects erosion rates

• farmers use more chemical fertilisers which causes the water chancels to become clogged with vegetation

what are physical causes of flooding?

• sudden rise in temperature, a rapid thaw can happen and rivers are unable to cope with the amount of water

• dams may burst which causes excess water in river channels causing flooding of large area

• cloudburst in a thunder storm, rains droplets fall quickly and there is no time for water to sink into ground

what are human causes of flooding?

• removal of vegetation means less interception so water will move to the river more quickly

• storm drains allow water to reach rivers at a quicker rate so flooding more likely

• global warming, melting of polar ice caps and rise in sea levels, flooding in low lying coastal areas

what are the effects of river flooding on people?

• damages farmland so lack of food

• damages to houses

• loss of life from drowning

• disruption to gas and electricity supplies

what are the effects of flooding on the environment?

• animals may be drowned

• natural vegetation is lost

• farm land is flooded so all crops are lost

what are three examples of hard engineering river strategies?

dams and reservoirs

channelisation

embankments

what are 2 examples of soft engineering river strategies?

floodplain zoning

washlands

what are dams and reservoirs? (adv and disadv)

huge walls built across rivers

Advantages:

• stores water which reduces flooding

• water in reservoir can be used as drinking water

disadvantages:

• very expensive

• can flood existing settlement

what is channelisation? (adv and disadv)

involves river channel being widened or deepened

advanatages:

• can hold more water

• water moves out of area more quickly

disadvantages:

• flooding may happen downstream as water moves quickly

• increases erosion

what are embankments?(adv and disadv)

raising banks of river so it can hold more water

advantages:

• more water can be held

• improves river as a shipping route

disadvantages:

• very expensive

• may cause downstream flooding

what is floodplain zoning?(adv and disadv)

prevents building on parts of land that are likely to flood

advantages:

• impermeable surfaces aren’t created

• less impact of flooding as less building

disadvantages:

• limited space for expansions

• no help in areas which are already built on

what are washlands?(adv and disadv)

areas which are deliberately allowed to flood

advantages:

• store water when river discharge is high

• provides wetland habitats

disadvantages:

• areas cant be used for farming or building