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Summary Geography geomorphology notes
Geography geomorphology notes
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Geography 2020Topic 2 – Geomorphology
GEOMORPHOLOGY IS THE SCIENTIFIC STUDY OF NATURE AND HISTORY OF THE LANDFORMS ON THE SURFACE OF EARTH.
UNIT 1
DRAINAGE SYSTEMS IN SOUTH
AFRICA
KEY TERMS
- DRAINAGE BASIN : THE TOTAL AREA OF LAND SURFACE DRAINED BY A STREAM NETWORK
- CATCHMENT AREA : THE AREA OVER WHICH RAIN FALLS THAT IS CAUGHT BY A DRAINAGE BASIN
- RIVER SYSTEM : A MAIN RIVER WITH ALL ITS TRIBUTARIES
- WATERSHED :AN AREA OF HIGH GROUND, SEPARATING TWO DRAINAGE BASINS
- TRIBUTARY : A RIVER THAT JOINS ANOTHER LARGE RIVER
- RIVER MOUTH : SEA OR LAKE WHERE THE RIVER ENDS
- SOURCE : WHERE THE RIVER BEGINS
- CONFLUENCE : THE PLACE WHERE TWO RIVERS JOIN
- WATER TABLE : THE UPPER LEVEL OF UNDERGROUND SATURATED ROCK
- SURFACE RUN-OFF : THE SURFACE FLOW OF WATER
- GROUNDWATER : WATER FOUND / SOURCED UNDER THE GROUND
- INTERFLUVE : HIGH-LYING AREA OR SPURS BETWEEN TWO RIVER VALLEYS
- INFILTRATION : THE MOVEMENT OF WATER THROUGH SOIL TO THE GROUND
- PERMANENT RIVERS : RIVER THAT FLOWS ALL YEAR ROUND
- PERIODIC RIVERS : ONLY FLOWS DURING RAINY SEASON AND OCCASIONALLY RUNS DRY
- EPISODIC RIVERS : FLOWS AFTER A HEAVY RAIN
,- EXOTIC RIVERS : RIVER THAT BEGINS IN THE REGIONS OF HIGH RAINFALL AND FLOWS INTO DRY REGIONS
- DENDRITIC PATTERN : TREE-LIKE STREAM PATTERN
- TRELLIS PATTERN : PATTERN THAT DEVELOPS IN AREAS OF SIMPLE FOLDED SEDIMENTARY ROCKS, OR GENTLY SLOPING
ALTERNATING LAYERS OF HARD AND SOFT ROCK
- RADIAL PATTERN: PATTERN THAT DEVELOPS WHEN RIVERS FLOW AWAY FROM A HIGH CENTRAL POINT SUCH AS A DOME;
VOLCANO; BUTTE ; OR MESSA
- RECTANGULAR PATTERN :PATTERN THAT HAS 90 DEGREE BENDS SO THE TRIBUTARIES BEND AT RIGHT ANGLES
- CENTRIPETAL PATTERN : STREAMS FLOW TOWARDS A CENTRAL BASIN OR LOW-LYING AREA , SUCH AS A MARSH, LAKE OR PAN
- DERANGED PATTERN : SMALL STREAMS THAT HAVE NO SPECIFIC PATTERN, MARSHY AREAS AND NUMEROUS SMALL LAKES
- PARALLEL PATTERN :STREAMS FLOW PARALLEL TO EACH OTHER FOLLOWING THE DIP OF THE LAND
- DRAINAGE DENSITY : THE AVERAGE LENGTH OF STREAMS IN THE AREA OF A DRAINAGE BASIN
- STREAM ORDER : RANKING SYSTEM WHICH DESCRIBES AND COMPARES DRAINAGE BASINS
- RIVER DISCHARGE : THE VOLUME OF WATER THAT FLOWS DOWN A RIVER
- LAMINAR FLOW : SMOOTH FLOW OF WATER INTO A RIVER
- TURBULENT FLOW : BUBBLING FLOW OF WATER ON UNEVEN RIVER BED
,WHAT ARE THE CHARACTERISTICS OF A DRAINAGE BASIN
• A drainage basin acts as a system with inputs, flow, storage and outputs.
• Water and sediment move through the system.
• Features of the system depend on a variety of physical and human factors.
• A drainage basin is the total area of land surface drained by a stream network.
Features of drainage basins
• Catchment area
• River system
• Watershed
• Tributary
• River mouth
• Source
• Confluence
• Water table
• Surface run-off
• Groundwater
• Interfluve
• Infiltration
, Different types of rivers
• TYPE OF RIVER IS INFLUENCED BY THE PREVAILING CLIMATIC CONDITIONS.
• CLIMATE DETERMINES THE AMOUNT AND SEASON OF PRECIPITATION AS WELL AS THE FORM (RAIN OR ICE).
• BECAUSE OF VARIED CLIMATES AND RAINFALL PATTERNS, FOUR TYPES OF RIVERS EXIST.
1. PERMANENT RIVERS
• Located in humid climates where the rainfall (precipitation ) exceed the evaporation rates.
• Flow all year round.
• Usually empty into larger bodies of water.
• Mainly found on the south and east coast of South Africa.
• All major rivers are permanent.
• Also influenced by the warm Mozambican (Agulhas ) current. Causes the warm humid climatic
conditions.
• Examples : Tugela river.
2. PERIODIC RIVERS
• Located in arid climates where evaporation rates exceed the precipitation rates.
• Only flow in rainy season and occasionally run dry.
• Filtration rates are higher.
• Often do not reach the sea.
• Found mainly in the interior of South Africa.
• Also influenced by the cold Benguela current, causes the cold, dry climatic conditions.
• Example : Limpopo river; Vaal river ( and its upper reaches)
3. EPISODIC RIVERS
• Only flow after heavy rain.
• Actually are run- off channels of very dry regions.
• Found in regions where there is low rainfall which evaporates quickly.
• Very rare type of stream.
• Only found in the arid western parts of South Africa.
• Examples : Auob and Nossob rivers in the south western parts of the Kalahari.
4. EXOTIC RIVERS
• Span two types of climatic regions : usually begin in regions of high rainfall and flow into dry regions.
• Largest types are large enough for them to receive enough water at their sources to enable them to
reach the sea.
• Examples: The Nile river : The Orange (Gariep) river which rises on the humid eastern side of South
Africa and flows through to the drier western side before it reaches the Atlantic ocean.
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