Geomorphology Grade 12

• Catchment Area


  The drainage area that supplies water to a river; the water comes from rainwater, which flows down the slope, and from underground water, which seeps into the river.
• Drainage basin 


  Area drained by a river system
• source 


  Place where a river begins
• Mouth


  Where the river flows into a sea or lake
• Surface runoff


  Rainwater flowing over the surface
• Watershed 


  High ground separating one drainage basin from the adjacent drainage basin
• stream or river network

  Individual streams and rivers that are connected
• Tributaries 


  Individual river channels forming the stream network
• Confluence 


  Point where one river in the network joins another
• Interfluves 


  Ridges of high ground between individual channels
• Overland flow


  Rainwater flowing over the surface
• Channel flow


  Water flowing in a river channel
• Throughflow 


  Water flowing through the soil
• Permeable rocks

  Rocks that allow water to seep in
• Groundwater


  Underground water
• Groundwater flow

  Water flowing through underground rocks
• Impermeable rock


  Rock without pore spaces or cracks through which water is able to pass
• Water table


  Upper surface of the groundwater
• Baseflow


  Groundwater that seeps into a river
• Permanent rivers 


  flow throughout the year because the water table is above the ground and constantly supplied with water
• Periodic rivers


  flow during periods of rainfall (the rainy season) only. The water table rises above the ground during the rainy season and forms these rivers.
• Episodic rivers

  These flow during periods of heavy rainfall only.
• Exotic rivers


  start in an area of high rainfall. There is a constant supply of water from their upper reaches and then they flow through semi-arid or arid areas.
• Radial pattern


  Develops on a dome where streams flow outwards and downhill
• Trellis pattern 


  Forms on inclined strata that are unequally resistant to erosion, or in areas where there are parallel fold mountains
• strata

  Inclined rock layers
• Rectangular pattern 


  Forms on igneous rock that has joints and crack; the streams develop right angled bends where joints meet
• Centripetal pattern 


  Streams flow into a central pan or low-lying area
• Dendritic pattern 


  Has a treelike appearanc; forms on rocks of similar hardness in an area with a similar gradient
• Parallel pattern 


  Develops on a surface that slopes uniformly but is fairly steep; the river and its tributaries flow downslope nearly parallel to each other
• Deranged pattern


  no apparent drainage pattern
• Drainage density 


  Total length of streams per unit area of a drainage basin
• Stream order

  The category of a stream in a network determined by the order of the streams feeding into it
• Discharge 


  The amount of water flowing in a river channel past a point in a given time
• Laminar flow


  Water flowing in sheets; it does not change levels
• Turbulent flow 


  Water flowing in a bubbling motion; it changes levels