Notes on the section of Fluvial Geomorphology for the 2020 IEB Final Exams
Includes detailed summaries and notes on sections such as important concepts, definitions, calculations, fluvial processes, fluvial landforms, river grading, river capture and abstraction.
Created by an A Geography student
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GEOMORPHOLOGY
CHAPTER 1: DRAINAGE SYSTEMS IN SOUTH AFRICA
IMPORTANT CONCEPTS
Drainage basin – entire area drained by a river and its tributaries
Watersheds – ridge of high land that separates two drainage basins
Interfluves – the area of higher ground separating tributaries
Catchment area – refers to all water in the drainage basin: both ground and
surface water
Tributaries – smaller rivers joining main river
Confluence point – point where the tributary joins the main river
Porosity – number of holes in rock
Permeability – ability of rock to allow water to pass through
Source – start of the river
o high mountainous area
o may develop at a spring
o may be result of meltwater
o may be the point furthest away from where it joins another river
Mouth – end of the river
o Point where river enters sea or other large body of water
o Deposition
o Delta or estuary
Water table – the upper level of groundwater
Surface water:
o Flows on the earth’s surface
o Remains after losses through evaporation, infiltration and surface retention
o Initially flows as sheetwash/sheet flow
o Direct runoff
Ground water:
o Infiltrates into earth’s surface
o Occurs in rocks that allow water infiltration aquifers
o Collects in cracks and pores of the earth’s crust
o Gravity forces water deeper into crust
o Indirect runoff
o Soil water – water that infiltrates soil
o Zone of intermittent saturation – pore space is filled up with both air
and water
o Zone of intermittent saturation – all pore space is filled with water
Water table will:
o Rise after high rainfall & drop in drought
o May intersect with earth’s surface at bottom of river baseflow
o May intersect with earth’s surface on side of hill spring
Factors influencing infiltration:
o Precipitation – greater rain and or soft soaking rain greater infiltration
o Evaporation – dry, hot and windy more evaporation lesser
infiltration
o Gradient – steeper rapid runoff lesser infiltration
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, o Vegetation – runoff is trapped by vegetation/shade (less evap.)
infiltration decreased
o Moisture in soil – saturated soil cannot absorb water lesser infiltration
o Porosity & permeability – if rock is both porous and permeable
greater infiltration
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