This is notes on Geomorphology topic in IEB Geography. The notes have images and descriptions that a consise whilst providing a good understanding of the topic. Best for revision and exam prep
TERMINOLOGY
- Drainage basin
- Catchment area
- Main river channel
- Watershed
- Tributary
- River mouth
- Source
- Confluence
- Water table
- Surface run-off
- Groundwater
- Interfluve
- Infiltration
- Saturated zone
- Base flow
WATER CYCLE
Precipitation - rain
Run off
1. Sheet flow 2. Streamflow
Water flows over land water flows in distinct channels called rivers or streams
NOT all precipitation becomes run off
Can occur as:
➢ Interception: water is intercepted by vegetation
➢ Retention: water is retained on the surface
➢ Evaporation: water evaporated back into the atmosphere
➢ Evapotranspiration: water is given off by plants and then evaporates
➢ Infiltration: water seeps into the ground
GROUNDWATER
Water seeps underground
Throughflow
Baseflow
PERMEABLE NON-PERMEABLE
➢ Absorbs water Does not absorb water
➢ Aquifer Aquiclude
*percolate- filter gradually through porous (has holes) surfaces
Factors that influence run-off
1. Relief- steepness
2. Soil type
3. Rock type- permeable vs non-permeable
4. Soil moisture
5. Vegetation
6. Rainfall
GEOGRAPHY Page 1
, 6. Rainfall
7. Land use- urban areas
WATER TABLE
Water table- boundary between water saturated and
unsaturated ground
Groundwater- seeps into river when the table lies above
the river bed aka as baseflow
TYPES OF RIVERS
NAME CHARACTERISTICS EXAMPLES
Permanent/Perennial • Flows constantly Vaal, Crocodile
throughout the year
• Humid climates
Periodic/ Non-Perennial • Flows only during rainy most
seasons
• Arid areas
Episodic • flows only after heavy rain, Swakop, Buffels
can be dry for years
• Desert areas
Exotic • Origin in a high rainfall area Orange River
and flows through an arid
region or desert
DRAINAGE PATTERNS
DRAINAGE DENSITY
Refers to the average length of the streams in the area of a drainage basin. Can be high or low
Drainage density =
Low stream order means:
> Greater number of segments
> Shorter the length of individual segments
> Greater total length of all the segments
> Steeper gradient of each segment
> Smaller size of the drainage basin
Drainage density depends on
Rainfall- high density in area of high rainfall
Infiltration and run-off
Underlying rock type
Amount of vegetation- more vegetation, decreases run-off
Slope- steep slope have more run-off
STREAM ORDER
Ranking system
GEOGRAPHY Page 2
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