River Systems SA

Question 1

what are the 4 types of rivers?

Answer 1

permanent rivers
periodic rivers
episodic rivers
exotic rivers

Question 2

discuss permanent rivers

Answer 2

flow throughout the year due to continuous base flow
occur in high rainfall areas
eg: Tugela River KZN

Question 3

discuss periodic rivers

Answer 3

flow every year during the rainy season when they receive run-off
dry up when water table drops in dry season
occur in semi arid areas
eg: most SA rivers

Question 4

discuss episodic rivers

Answer 4

flow occasionally when it rains in a dry area
often does not reach sea
water table always below valley floor
eg: AUB and Nossob river

Question 5

discuss exotic rivers

Answer 5

flow continuously through dry areas because receive water from humid areas upstream
eg: Nile river

Question 6

what are the 7 stream patterns?

Answer 6

dendritic 
trellis 
rectangular 
radial
centripetal
deranged
parellel

Question 7

characteristics of dendritic stream pattern?

Answer 7

tree shaped pattern, tributaries join at acute angles from upstream

Question 8

characteristics of trellis stream pattern?

Answer 8

parallel main stream with tributaries joining at 90’ angles

main streams run along parallel valleys

Question 9

characteristics of rectangular stream pattern?

Answer 9

tributaries and main streams have 90’ angles in the streams

Question 10

characteristics of radial stream pattern?

Answer 10

rivers flow in different directions from a central point

divergence

Question 11

characteristics of centripetal stream pattern?

Answer 11

streams flow to a central point

convergence

Question 12

characteristics of deranged stream pattern?

Answer 12

no apparent pattern visible

many lakes, marshes appears randomly

Question 13

characteristics of parallel stream pattern?

Answer 13

tributaries run nearly parallel to each other and join main stream at acute angles

Question 14

how does one determine stream order?

Answer 14

All origin streams are order 1. stream order increases when 2 of the same order stream meets. Order 1 plus order 1 equals order 2 stream and so on. In South Africa maps, no bigger than order 4 streams.

Question 15

what is river discharge?

Answer 15

refers to the amount of flow in a river passing a specific point at a specific time. measured in metres cubed per second

Question 16

what is laminar flow?

Answer 16

water flows in layers over each other and surface of river looks smooth. occurs in wide smooth channels with gradual gradient

Question 17

what is turbulent flow?

Answer 17

water flows in circular patterns and surface looks white and bubbly. occurs in narrow rough channels with steep gradient

Question 18

what factors determine a drainage basin?

Answer 18

relief 
soil type
rock type
soil moisture
vegetation
rainfall