Geography notes grade 12

Impact of river capture on captor stream and captured stream

Captor Stream:

Larger drainage basin and catchment areas
Will have more water / larger volume
More erosive power / more energy
Downward erosion
Rejuvenation due to renewed energy
Carrying capacity will increase
Larger stream load
Knick point develop at point of capture

Captured Stream:

Smaller drainage basin and catchment areas
Will have less water / smaller volume
Less erosive power / less energy
Deposition takes place
Carrying capacity diminished
Less stream load
Misfit stream too small for valley
River gravel develop deposited in wind gap

Features associated with river capture

☆ Captor stream / Pirate stream: the stream that has more erosive power and cuts through the watershed to capture the other stream.

☆ Captured stream: the stream that loses its headwater to another stream.

☆ Misfit stream: The stream that has lost its headwaters and in now too small for the valley that it flow in.

☆ Elbow of capture: the sharp angle where stream capture took place.

☆ Wind gap/River gravels: the area where the captured stream dries up and deposition take place just after the point of capture.

RURAL SETTLEMENT

SETLLEMENT IS A GROUP OF BUILDINGS ,PEOPLE , ACTIVITIES AND COMMUNICATION NETWORK THAT FUNCTION AS A SINGLE INTERGRATED SYSTEM.

A SETTLEMENT CAN EITHER BE A RURAL OR URBAM . A RURAL SETTLEMENT IS FUNCTIONAL WHILE AN URBAN SETTLEMENT IS MULTIFUNCTIONAL.

Negative impact of flooding on local communities

*Washes away the crops
*Reduce the fertility of the soil
*Increase the rate of soil erosion
*Triggers mass movements
*Endangered animal and human life
*Contaminates drinking water
*Can cause hunger and starvation
*Loss of capital income
*Higher food pricess
*Leave some people homeless
*Import food-negative trade balance

Sustainable management of a drainage basin

*Build artificial levees
*Build large storage dams to control flow
*Plant tress to increase infiltration and reduce run-off
* Prevent building on flood plains

Measures to restore the drainage basin
# REVEGETATION AND AFFORESTATION
USE IF MANURE AND COMPOST TO INCREASE INFILTRATION
PLOUGHING CLOSE TO THE RIVER
APPROPRIATE METHODS OF AGRICULTURE E.G CONTOUR PLOUGHING TERRACING SLOPES
of catchment areas
Avoid over grazing
OVER GRAZING
# AVOID CONSTRUCTION ON FLOODPLAINS
OF GROUND WATER SUPPLY

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Urban settlement

URBANIZATION is the process whereby an ever-increasing percentage of the total population is accommodated in urban settlement

URBAN EXPANSION is an increase in the number of buildings showing a physical or areal extention of an urban settlement

URBAN GROWTH is an increase in the number of urban residents due to high birth rates and migration.

VALLEY WINDS

These occur during the day

The sun's rays heat up the valley slopes during the day

The warm ,light air above the slopes rises up the slope

Anabatic air is important because it assists in releasing the pollutants from the valley .

Berg winds
These are very hot and dry winds that blow mostly during winter and Autumn towards the coastal areas . They are caused by descending winds from a high pressure cell that has developed in the north easten interior. As the winds descend over the inland plateau towards the coast.

Effects of berg winds

# increases the temperature of the coastal areas
# decreases the atmospheric humidity
# development of run-away fires increases

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RIVER MOUTH
THE RIVER MOUTH IS WHERE THE RIVER ENDS , E.G. IN THE SEA OR A LAKE WATER IN A RIVER SYSTEM ALWAYS FLOWS FROM HIGH LAND TO LOW LAND .THE TRIBUTARIES OF A RIVER SYSTEM ALL JOIN TOGETHER TO FORM ONE LARGE RIVER IN THE DRAINAGE BASIN . THERE IS THEREFORE USUALLY ONLY ONE RIVER MOUTH IN A DRAINAGE BASIN

SOURCE

THE SOURCE OF A RIVER IS WHERE THE RIVER BEGINS ,e.g. A SPRING OR A HIGH -LYING AREA A RIVER SYSTEM WILL HAVE A NUMBER OF DIFFERENT SOURCE AS EACH TRIBUTARY WILL HAVE ITS OWN RIVER SOURCE .

CONFLUENCE

THE CONFLUENCE IS WHERE ONE RIVER JOINS ANOTHER RIVER .THE NUMBER OF CONFLUENCES FOUND IN A DRAINAGE BASIN WILL BE DETERMINED BY THE NUMBER OF TRIBUTARIES.

SURFACE RUN-OFF

THE RUN-OFF OF A RIVER REFERS TO THE AMOUNT OF WATER THAT FLOWS IN ALL THE TRIBUTARIES OF THE RIVER SYSTEM .THE AMOUNT OF WATER THAT PASSES TROUGH THE RIVER SYSTEM IS REFFERD TO AS THE VOLUME OF WATER IN A DRAINAGE BASIN .

GROUND WATER

WATER THAT INFILTRATES UNDERGROUND IS CALLED GROUND WATER. WATER SEEPS INTO THE SOIL THROUGH THE PROCESS OF INFILTRATION.THE MOVEMENT OF WATER THROUGH THE GROUND IS CALLED PERCOLATION.

WATER TABLE
THE TOP SURFACE OF THE SATURATED WATER ZONE IS CALLED THE WATER TABLE .THE WATER TABLE CHANGES WITH THE SEASONS

*WHEN THERE IS MORE RAINFALL IT WILL BE AT HIGHER LEVEL
*DURING A DRY PERIOD ,IT WILL BE AT A LOWER LEVEL

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DRAINAGE BASIN

A drainage basin is an are of land from which a river and it's tributaries get their water e.i the water drains from the basin into the river and it's tributaries .

Drainage basins differ in terms of their size shape and volume

CATCHMENT AREA
the catchment area is another name for a drainage basin -the area which has the precipitation that feeds the river s in the drainage basin

RIVER SYSTEM
the river system refers to the main river and all its tributaries that are found in the drainage basin.

WATERSHED
An are of high land called a watershed , separates one drainage basin from another.the are of land between on river TRIBUTARY and another in a river system called an INTERFLUVE.

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How site and situation affect the location of rural settlements
👉People will settle in a rural area for a number of reasons,according to it's size and situation.

Factor affecting site
-water
👉It is a basic need , making it viral for any rural settlement.
👉Rural settlement engage in primary activities that require -water .
👉If water is scarce,the settlement will be nucleated around the water source.
👉If water is plentiful the settlement will be more dispersed

Relief
👉Flat areas are better for farming and development so rural settlement are more likely to develop on plateaus or gentle slopes
👉If defence is important ,a rural settlement may develop on a hilltop

Aspect
👉Aspect is the direction in which a slope faces .it is very important in farming and forestry activities.
👉In the southern hemisphere north-facing slopes are warmer which may result in the development of farming settlements on these slopes

Soil
👉 For farming settlements the quality of the soil is an important function in deciding on the side of a settlement .
👉Good quality soil is a major attraction for a farming community.

Climate
👉Rural settlement are less likely to develop in areas with extreme weather conditions .
👉Farmers and foresters will settle in areas where the climate is conducive to their type of crop or animal.

Complexity
👉Is the combination of services and structure in a settlement
Pattern
👉Is a settlement pattern refers to the shape and layout of the settlement interms of where the actual buildings and services are situated within that settlement.

Function
👉The function of a settlement refers to the type of economic activity and the number of activities that take place in the settlement .

Settlement classification according to size ,complexity , pattern and function

Settlement can also be classified according to the following
*Size :how large or small they are physically and the size of their populations
*Complexity:the combination of services and structures located there
*Pattern: what service the settlement provides or what purpose it fulfils

SIZE

settlements can be classified according to the actual size or the area of the land on which they are situated as well as the size of the population.

Settlements of different sizes are given different names
Megalopolis👉A gigantic urban area that forms when many conurbations and metropolises join together

Conurbation👉the joining together of many towns and cities to form one large urban are :as Johannesburg Midland and Pretoria begin to merge ,they will jointly become known as a conurbation

Metropolis👉is a city that is surrounded by many independent towns such as la Lucia ,westville and pinetown
City👉 large town that offers a variety of services that have specific functions such as administrative , financial and judicial

Town👉refers to a densely populated urban area
Village👉a large population than a Hamlet ;most people are involved in Farming but the settlement does have a supply store
Hamlet👉small groups of farmsteads
Farmstead👉an isolated settlement that is usually on a farm.

Concept of settlement

Site
*This refers to the precise geographic position of the settlement of with respect to the physical environment.

Situation
*this refers to the position of the settlement in relation to the surrounding environment.

Rural and urban settlement

Rural settlement focus on primary activities with fewer services
* Whereas urban settlements are typically large with a wide range of economic activities.

Rural settlements are considered to be the countryside and provide a far smaller
Range of services compared to urban settlement they are characterized by the primary economic activities ÷
•farming
•fishing
•forestry
•mining
•hunting

Urban settlements are multi-functional which means that they fulfil many needs and provide and wide range of services . traditionally,urban settlements provide more SECONDARY , TERTIARY AND QUATERNARY ECONOMIC ACTIVITIES

QUATERNARY ACTIVITIES: SERVICES INVOLVING RESEARCH,LIBRARIES AND INFORMATION TECHNOLOGY

TERTIARY ACTIVITIES: THE PROVISION OF SERVICES

SECONDARY ACTIVITIES:THE MANUFACTURING OF GOODS OUT OF RAW MATERIALS

PRIMARY ACTIVITIES: THE EXTRACTION OF RAW MATERIALS DIRECTLY FROM THE EARTH

SETTLEMENTS CAN BE CLASSIFIED ACCORDING TO THE FOLLOWING
SIZE- HOW LARGE OR SMALL THEY ARE PHYSICALLY AND THE SIZE OF THEIR POPULATION

COMPLEXITY-THE COMBINATION OF SERVICES AND STRUCTURE LOCATED THERE

PATTERN-THE SHAPE OR THE LAYOUT OF THE SETTLEMENT

FUNCTION - WHAT SERVICES THE SETTLEMENT PROVIDES OR WHAT PURPOSES IT FULFILS

Drainage patterns

Types of drainage patterns

1 dendritic
-the river tributaries join the main river like the branches of a tree ,this is the most common drainage pattern and is found in the basins having one rock type with no variation in structure

Trellis

The main streams are parallel with short,steep river tributaries that join the main stream at roughly 90°,trellis drainage is common in areas which are fold mountains

Rectangular or angular
This pattern has streams and their tributaries with many sharp bends all join at 90°. This is common in areas which have been faulted or in areas where the rock structure is jointed

Redial
The streams radiate outwards from a central high land area like spokes of a wheel . This is common in areas with volcanoes , or where there are isolated hills ,such as a butte or a dome.

Centripetal
This pattern is opposite to radial patterns,where streams flow downwards to a central depression or low lying area . Centripetal formation is common in areas where land has been wrapped and dips down

Deranged

This pattern has no fixed shape.it is characterized by small irregular streams ,swampy areas and many small lakes . It is common in recently glaciated areas where a drainage pattern has not had time to develop
Parallel
This is the simplest pattern where streams flow parallel to each other ,following the dip of the land .this is common in areas of uniformly sloping rock

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Types of rivers

There are many river valleys that do not have water flowing in them . Some rivers flow all year round , other only flow when it rains

*Permanent rivers: these are called perennial Rivers because they flow all year around for an example the Tugela river,the Amazon river and the Mississippi River.

*Periodic rivers :these are called non-perennial rivers because they do not have a constant flow they usually flow during rainy season for example the fish river in the Namibia

Episodic rivers:these non-perennial rivers flow during periods of heavy rainfall .they are usually in very dry ,arid areas and they may not flow for a few years at a time for example the nossob river in the Kalahari desert

* Exotic rivers : these Rivers are perennial Rivers flowing through dry areas of the land .they have a permanent supply of water because the source of these Rivers is in a well watered region for an example the gariep-orange river.....

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Source

The source of a river is where the river begins .
A river system will have a number of different sources as each TRIBUTARY will have its own river source.

Confluence

The confluence is where one river joins another river the number of confluences found in a drainage basin will be determined by the number of tributaries

Surface run-off

The run-off of a river refers to the amount of water that flows in all the tributaries of the river system . The amount of water that passes through the river system is referred to as the volume of water in a drainage basin

Groundwater

Water that infiltrates the underground is called groundwater.water seeps into the ground soil through the process of infiltration. The movement of water through the ground is called percolation . This groundwater flows downhill because of the gravity

A saturated water zone is reached when water fills all the pores in the rock or when water collects above an impermeable rock layer .

Water table

The top surface of the saturated water zone is called the water table .the water table changes with the seasons
*When there is more rainfall it will be at a higher level
*During a dry period it will be at a lower level.

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Site and situation
The site and situation of a settlement refer to where it is located

Site
This refers to the precise geographic position of the settlement with respect to the physical environment

Catchment area

The catchment area is another name for a drainage basin -the area which has the precipitation that feeds the rivers in the drainage basin

River system

The river system refers to the main river and all its tributaries that are found in the drainage basin

WATERSHED

An area of high land ,called a WATERSHED , separates one drainage basin from another the area of land between one river TRIBUTARY AND ANOTHER in a river system called an INTERFLUVE.

The river mouth
The river mouth mouth is where the river ends

Conditions necessary for the formation MID-LATITUDE CYCLONES

* FOR MID-LATITUDE CYCLONES (DEPRESSIONS) TO FORM TWO DIFFERENT STRENGS OF THE AIR MASSES NEED TO MEET IN AN AREA OF LOW PRESSURE . THIS OCCURS ALONG THE POLAR FRONT(the subpolar low pressure area).

AREAS where MID-LATITUDE CYCLONES FORM WHEN TWO DIFFERENT AIR MASSES MEET AT A FRONT . THE COLD POLAR AIR FROM THE POLES ( POLAR EASTERLIES) AND THE WARM TROPICAL AIR FROM THE EQUATOR(WESTERLIES)

General characteristics

*MID-LATITUDE CYCLONES MOVE FROM WEST TO EAST
*THEY ARE LARGE SYSTEM RANGING FROM 1600 T0 2400 KM.
* THEY MOVE OVER LARGE DISTANCE BEFORE THEY DISAPPEAR .
*THEY OCCUR THROUGHOUT THE YEAR .
*THEY ARE LOW LOW PRESSURE SYSTEM ASSOCIATED WITH UNSTABLE CONDITIONS
*THEY BRING CLOUD.COLD AND RAINY WEATHER.

cold front conditions

* temperature decreases
*humidity decreases
*cloud cover increases
*wind direction changes and with strong winds

stages of mid -latitude cyclone
*initial stage-
warm pressure difference exist between the warm tropical air and cold polar and warm polar air resulting in a pressure gradient( around polar front)
- due to a disturbance in winds high in the atmosphere or mountain ranges a wave forms
- a low pressure cell increases
*mature stage
-polar front forms cold and warm front
- fronts divide area into cold and warm sector
* air flow Around low pressure cell
- clock wise in the southern hemisphere
- anti clock wise in the northernhemisphere

*concluded stage

Phenomena associated with tropical cyclones

STORM SURGE

Storm surge is simply water that is pushed towards the shore by the force of the winds swirling around the storm this advancing surge combined with the normal tides to create the hurricane storm tide ,which can increase the average water level 5.4 or more

Inland flooding
In addition to the storm surge and high winds . tropical cyclones bring torrential rains and flooding in area.even after the wind has diminished , the flooding potential of these storms remains for several days .floods may destroy agricultural land and cattle , infrastructure and causes more deaths as a result of drowning

OCCLUDED STAGE

* Cold front over takes warm front resulting in only cold air on the ground ( lighter warm air is pushed up)

MATURE STAGE
* Air flows around low pressure cell
-clockwise southern hemisphere
-ANTI CLOCKWISE IN THE NORTHERN HEMISPHERE
* Polar front forms cold and warm front
*fronts divide area into cold and warm sector

Stages of development of the MID-LATITUDE cyclone
Initial stage

*Pressure differences exist between the warm tropical air and cold polar air and cold polar air resulting in a pressure gradient (around polar front) due to a disturbance in winds high in the atmosphere or mountain ranges a wave forms
* A cell of low pressure begins

Cold front condition!

*Temperature decreases
*Pressure decrease but it increases with the cold sector
*Humidity decreases
*Cloud cover increase
*Wind direction changes with strong winds