drainage basins

waterfalls

-a common landform found in the upper course of a river -this is a vertical or near vertical drop along the course of a river - waterfalls commonly occur where hard rock overlies soft rock(it can be horizontal,vertical or inclined) -when a waterfall retreats due to headward erosion it can result in the formation of a gorge(this is a very deep valley with steep side - a plunge pool forms at the bases of a waterfal due to the force of the falling water and debris which erodes the base to form a depression

factors influencing drainage density

-amount of rainfall -gradient( slope) -permeability -porosity -soil moisture -vegetation

radial centripetal of underlying of underlying rock structures

-associated with massive igneous rocks

NB

-base level of a river changes when the sea level rises or drops -when sea level drops it results in the gradient of the river becoming steep,the speed of the water increases and the rate of erosion increases.This process is called rejuvination

types of drainage patterns

-dendritic -rectangular -radial centrifugal -radial centripetal -trellis -parallel -deranged/intermittent

importance of managing drainage basins/catchment areas

-farming takes place on floodplains and deltas because of fertile silt that is foud here.Water is also used from the river channel in irrigation schemes -rivers are used to generate hydro-electric power -transport of goods and people using boats and barges -leisure activities such as fishing,canoeing and white water fating -rivers are also a tourist attraction especially when they have attractive features such as waterfalls and lakes -it supplies fresh water for domestic and industrial use -to ensure that ecosystems remain healthy and in balance -to protect water usage for present and futrure generations(sustainable use)

strategies to manage drainage basins/catchment areas

-fines to be imposed for dumping into rivers -create a buffer zone close to rivers to prevent industiural development being too close -encourage the growth of vegetation and trees to trap surface run-off and decrease erosion. -frequent testing of water quality to prevent disruption of ecosystems -encourage the recycling of waste rather than dumping into rivers -to educate farmers on sustainable practises -wetland must conserved awareness campaigns and legislation to prevent dumping into rivers

permanent

-flows all year round -associated with high rainfall areas

episodic

-flows only after a heavy rainfall or thunderstorm -the river only flows for a few hours -characteristic of acid rain

periodic/sesonal

-flows only in the rainy season -characteristic of area with high summer rain and dry winters

oxbow -lake

-form from a meander loop that is cut off from the mainstream -erosion on the outer bank and deposition on the inner bank of the meander results in the meander neck becoming narrower -during times of flood the water cannot negotiate the meander loop and flows straight -this results in the loop being cut from the main river to form an oxbox lake -the oxbow lake will eventually dry up to form a meander scar because it does not have a water supply.

rectangular pattern underlying rock structure

-forms on igneous rocks that have many joints -also forms in horizontal sedimentary rocks with many joints and faults

underlying structure of trellis pattern

-forms on rocks which has varying resistance to erosion -found in fold mountain regions and areas of inclined strata -associated with sedimentary rocks which has alternate layers of hard and soft rock

braided stream

-forms when a river deposits its load and blocks its own path and is forced to split into smaller channels -this feature is formed by a seasonal river that has an abundance of bed load which is deposited in the lower course -gentle gradient in the lower course and the decreased river flow during the dry season slows down the river forcing it to deposit its load within its channel -continued deposition causes sand islands to be built on the bed.In this way the river obstructs its own path and it branches into smaller channels that weave their way around the deposited material.

disadvantages of deltas

-hard to make transport links by roads-costly to build bridges -areas are at constant risk of flooding -vulnerable to rising sea levels -water is often dirty and polluted -mosquitoes are attracted to water(malaria) -storm surges from tropical storms

process that a river undergoes to be graded

-in the upper course,downward erosion takes place to result in a steep slope -headward erosion removes the temporary base levels of erosion such as waterfalls -rapids are removed by downward erosion -the stream carrying capacity increases in the middle course,and obstacle such aas lakes are filled with the rivers load.More lateral erosion -in the lower course more deposition takes place because the gradient is gentler.This results in a gradual gradient. -the steep slope in the upper coursw,which gradually drops to a gentle gradient in the lower course results in a concave shape

river gravels

-in the wind gap,boulders,stones and pebbles are left behinnd due to the decreased volume of water in the river and are referred to as river gravels

abstraction

-is a process of the watershed changing its position. -it occurs when the watershed is steeper on one side as compared to the other -rivers that flow down the steeper side erode the landscape faster,thus changing the position of the watershed -eventually the gradient of the watershed is the same.

paired terraces

-it forms as a result of downward erosion(down-cutting) -the floor of the old valley forms a terrace on either side of the river.

delta

-it forms at the point where the river enters the sea and deposits its load -he current of the river keeps fine sediments such as clays and silts in suspension -the saline conditions in the sea cause fine clay particles to flocculate(stick together) making the particles larger and heavier which then sink

underlying rock structure of deranged pattern

-it forms in areas that have been recently exposed or formed(geologically young)

radial centrifugal underlying rock structures

-it forms in areas where domes and volcanoes occur -it is associated with massive igneous rocks

superimposed drainage pattern

-it has a pattern that does not correspond with the structure of the existing surface that it flows over -the original rock structure is removed by erosion(e.g quartzite) and the river maintains its pattern over a different rock structure(e.g. granite) that was previously buried THE RIVER IS YOUNGER THAN THE UNDERLYING ROCK STRUCTURE THROUGH WHICH IT FLOWS

deranged /intermittent description

-it has haphazard patterns -there are many lakes and swamps -develops from the disruption of a pre existing drainage pattern

antecedent drainage pattern

-it is a river pattern that was formed on land before it was upldifted as a result of earth movements(folding or faulting) -the river maintains its general course in spite of the land being uplifted THE RIVER IS OLDER THAN THE UNDERLYING ROCK STRUCTURE THROUGH WHICH IT FLOWS

flood plains are useful to man because:

-it is extremely fertile and can be intensely cultivated -the land is flat and encourages the use of machinery -the river provides a regular supply of water for cultivation -in areas that are not prone to flooding settlements develop because it is easy to construct roads and buildings.

elbow of capture

-it is generally a right angle bend which indicates the point where one river captures another

ungraded river profile

-it is uneven and has many obstacles along the course of the river e.g waterfalls,rapids,dams,lakes and resistant rocks.

underlying of parallel drainage basin

-it occurs in areas of major faults -areas of steeply folded bedrock -resistant rock bands

wind gap/dry gap

-it refers to a dry river valley that is found immediately below the elbwo of capture

misfit river/beheaded stream

-it refers to a stream that has too little water for the valley within which it flows

impact of pollution on rivers

-loss of oxygen:the breakdown of raw sewerage in water uses of a lot oxygen.this reduces the amount of oxygen available to plants and animals living in the water and thus destroys them. -eutrophication:this term describes an increase in nitrate levels in a river which results from agricultural wastes.It encourages the growth of algae which in turn uses up oxygen and decreases the amount of light entering the water.The water turns green and affects other life in the water/

a drainage basin can be described as

-low -medium -high density

features of river capture

-misfit/beheaded stream -elbow of capture -wind gap or dry gap -river gravels

dendritic pattern underlying rock structure

-occurs on rocks that have a uniform/equal resistance to erosion -associated with horizontal sedimentary and massive igneous rock.

temporary base level

-occurs when a river flows into a dam,over a waterfall,into a lake etc.These features temporarily prevent the river from further vertical erosion

exotic

-originates in areas of high rainfall but flows through dry areas -these types of rivers commonly occur on the west coast of south africa.

types of rivers

-permanent -episodic -periodic/seasonal -exotic

rapids

-rapids are sections of rough turbulent(white water) water -they normally in a rivers upper course and are formed where there are layers of hard and soft rock. -the layers of soft rock erode quicker than the the layers of hard rock -this makes the bed of the river uneven creating rough turbulent water.

significance of rapids

-rapids can become popular with tourists who want to raft down stream -they are also extremely dangerous if people fall into them -these features cause problems with transport,ships cannot travel up and down rapids and it is very hard to build bridges across them

headward erosion

-refers to a river cutting backwards into the watershed towards its source.

floodplain

-refers to flat land that is found on the banks of a river. -it is made up of deposits of silt that has been built up after being subjected to repeated flooding.

captor stream

-refers to the river that has captured the water of another through headward erosion

captured stream

-refers to the river that has iits water diverted into another river

impact of urbanization on stream flow

-removal of vegetation to construct buildings,increases surface run-off and results in higher discharge over a short space of time.Water flow tends to be more turbulent -concrete sirfaces

description of dendritic pattern

-resembles the branch of a tree -tributaries join the main river at acute angles

radial centrifugal description

-rivers flow away from the central point such as a volcano or a dome -it resembles the spokes of a wheel

description of radial centripetal

-rivers flow toward a central point or depression -this central point could be a lake ,a pan or a basin

impact of river capture on the captured stream

-size of drainage basin decreases -volume decreases due to it being robbed of its head waters -flows slower due to a decrease in the volume of water -erosive ability decreases due to decreased flow -deposition increases as the river has less energy due to less water.

impact of river capture on the captor stream

-size of drainage basin increases -volume increases due to additonal water being diverted into its channel -flows faster due to an increase in the volume of water -erosive ability increases due to increased flow -the river could be rejuvinated

the effects of river capture on human activity and ecosystems

-the consequences of river capture on human activity and the environment will be different for the captor and the captured river: human activity:people who are settled along the lower course of the captured river will be disadvantaged in the follwoing ways: -less water will be available for agriculture casuing production to decrease -if the river is used for the generarion of hydro-electric power this activity will no longer be sustained -lowe volumes of water will be available for domestic and industrial use in an urban settlement -increased possibility of pollution and poor water quality. ecosystems:aquatic organisms perish since the supply of water is reduced.Food chains and food webs are disrupted and the ecosystems are thrown into a state of imbalance.

advantages of deltas

-the fertile land for farming,especially crops like rice -plenty of water for fishing or aquaculture.this can feed families or provide an income. -abundant drinking water -tourism opportunities -good transport links

rectangular pattern description

-the main stream have 90 degree bends along its course -the tributaries join the main stream at 90 degree

description of trellis drainage basin

-the main streams are parallel to each other -short ributaries join the main river at right angles -tributaries often flow from gaps or poorts

knickpoint waterfall

-the point where the old erosion level meets with the new. -sometimes waterfalls are formed where there is a sharp change in gradient

conditions necessary for deltas to form

-the river must have a large amount of sediment. -the sea must have weak currents and a small tidal range -the sea must be shallow at the rivers mouth

permanent or ultimate base level

-the sea is regarded as the permanent base level.IT IS THE LOWEST LEVEL TO WHICH A RIVER CAN ERODE.

facts on the water table

-the water table tends to be higher in summer because of higher rainfall. -other factors that give rise to a higher water table include:natural vegetation that traps surface water and increases infiltration,gentle slope ,permeable rocks and moist soils -the building of bore holes and wells would decrease ground water levels.

significance of waterfalls

-they form tourist attractions -can be used to generate hydro-electricity -danger from fast flwoing water(drowning) -it creates an obstacle along the course of the river and makes it impossible to use for navigation and recreational activities such as canoeing

rejuvination

-this is the process where a river which has reached based level,regains energy and begins to erode vertically(downwards) once again.The erosive power,speed,and arrying capacity of the river is renewed.

description of parallel drainage basin

-tributary streams tend to stretch out in a parallel-like fashion following the slope of the surface

reasons for rejuvination

-upliftment of the land due to internal movement such as isostatic uplift -volume of water in the river increases because of river capture -higher rainfall increases the erosive potential of the river -sea level drops and the river has to erode to a lower level

laminar flow

-water flows i thin layers that glide smoothly over each other -there are no rocks and boulders to cause friction between the water and the rocks -occurs when the river bed is even and gently sloping - has a low rate of erosion

turbulent flow

-water goes in complex tumbling circular movements -rivers have a rough and uneven bed -more energy is required to overcome these obstacles -has a high rate of evapouration

impact of people on drainage basins and catchment areas

afforestation-reduces stream discharge,but inhcresde ground water level.more deposition in the lower levels WASTE DISPOSAL-pollution affects the quality of water -changes equilibrium of the river and reduces river habitat -health hazard,people can become ill IRRIGATION-reduces water downstream -more deposition,reduces carrying capacity of river -increases surface run-off and deposits harmful substances such as salts and pesticides in the river.This could also increase the growth of algae in the water DAMS/CANALS/ARTIFICIAL-affects the flow of the river OVERGRAZING-the removal of vegetation in catchment arteas reduces infiltration and thus the amount of ground water available in the dry season URBANISATION-more aritifical substances results in greater surface run off,increasing discharge -encourages flash floods and flood peaks

drainage basin

area drained by a river and its tributaries

graded streams

develop over time as balance between gradient,velocity,discharge,channel,shapeand sediment load is reached.

drainage density

is a measure of the total length of streams per unit area -THE GREATER THE NUMBER OF STREAMS IN A BASIN,THE HIGHER THE DRAINAGE DENSITY WILL BE.

entrenched/incised meander

it forms from a meandering river that has cut a deep river that has cut a deep valley into the underlying bedrock.

graded river profile

it has a smooth concave profile.

watershed

it is a high lying area that separates two drainage basins

interfluve

land that separates streams in the same drainage basin

permeability

low density density: -permeable rocks allows more infiltration .Therefore less surface streams develop and density is low high drainage density: -impermeable rocks promote runoff.Therefore more surface streams will develop and density is high.

amount of rainfall

low drainage density -density is usually lowe in places that experience a dry climate, e.g. the arid region of the Karoo. high drainage density: -density is usually higher in places that experience a wet climate. e.g. East Coast of South Africa

soil mositure

low drainage density: -dry soils absorb water therefore stream runoff is reduced and drainage density is low. high drainage density: -infiltration is low in soils that have high moisture content. -more channels form due to greater surface run-off and drainage density is high

gradient(slope)

low drainage density: -gentle slopes increase the amount of infiltration into the ground thus resulting in lower drainage basin high drainage density: -steeper slopes increase the amount of runoff into streams casuing higher density

vegetation

low drainage density: -lots of vegetation cover results in greater infiltration into loos soils.This leads to lower drainage density high drainage density: -in areas where the vegetation has been removed by soil erosion,the formation of gullies is promoted therefore resulting in higher drainage density.

porosity

low drainage density: -rock tthat is porous will allow more infiltration,and less surface streams will develop therefore density is low high drainage density: -rock that is non-porous promotes runoff,therefore more surface strema swill develop and density is high

river mouth

point wher the river enters the sea

confluence

point where two or more rivers join or meet.

river system

refers to the main river and its tributaries

natural levees

refers to the naturally raised banks of a river -these form on the banks of river that have been subjected to repeated flooding -after the flood waters have receded it leaves behind gravel,sannd and silt which builds up to form raised bamk,which is refered to as a levee.

water table

refers to the upper limit of water that is found underground

catchment area

refers to the upper reaches of a drainage basin which supplies a river with water

discharge of a river

refers to thw flow of water in a river -the down slope of water in a river under the influence of gravity is either smooth or turbulent.The flow within most rivers is turbulent in the UPPER COURSE and laminar flow usually occurs in the LOWER COURSE.

tributary

smaller streams that join the main stream

river source

starting point of river

stream piracy/river capture

this is where one river captures /robs the headwaters of another river and so increases the size of its drainage basin.

surface run off

water that flows on the surface after it rains

ground water

water that is found within the earths surface

valley within a valley

a new valley is carved into the old valley.