rivers 1.1

Question 1

define drainage basin

Answer 1

or catchment area is the area of land drained by river and tributaries

Question 2

define water shed or divide

Answer 2

boundary of drainage basin
imaginary line separating one drainage basin from the next

Question 3

define source

Answer 3

start of river’s course usually on high land such as mountain

Question 4

define mouth

Answer 4

end of river
point at which flows to the sea

Question 5

define tributary

Answer 5

small river which flows into larger stream or river

Question 6

define confluence

Answer 6

point where tributary joins main river

Question 7

what is needed for river processes to occur within river

Answer 7

energy

Question 8

what is the river’s energy used for

Answer 8

most of it is used to overcome friction
remaining used to erode river channel and to transport material energy
the more energy a river has the greater its ability to erode its channel

Question 9

what is the amount of energy is determined by

Answer 9

volume of water flowing though river channel at any given point and measured in cumesc

Question 10

what causes greater energy of river

Answer 10

greater discharge
steeper gradient of river

Question 11

list three types of erosion along river

Answer 11

headward erosion
vertical or downwards
lateral sidewards

Question 12

define headward erosion

Answer 12

occurs near source and this makes river longer

Question 13

define vertical downwards erosion

Answer 13

also known as downcutting
often occurs in upper course of river
erodes river bed thus making river channel deeper

Question 14

define lateral sidewards erosion

Answer 14

typically occurs in middle and lower courses of irver
this is when the banks of river erode which widens river

Question 15

list the 4 erosional processes

Answer 15

hydraulic
abrasion corrosion
attrition
solution

Question 16

define hydraulic erosion

Answer 16

sheer force of water as hits the river banks pushes water into cracks trapping air within
air becomes compressed and pressure increases and river may in time collapse

Question 17

define abrasion

Answer 17

sediment carried by river scours bed and banks much like sandpaper
therefore rivers bedload acts as tool to erode river

Question 18

define attrition

Answer 18

as bedload moves downstream eroded rocks collide and break into smaller fragments
in time angular rock becomes smaller and more rounded as it moves downstream
no erosion of bed and banks of river

Question 19

define solution erosion

Answer 19

carbon dioxide dissolves in river to form a weak acid
this dissolved rock by chemical processes such as carbonation and solution
this process common where carbonate rocks such as limestone and chalk are evident in a channel

Question 20

list the four drainage patterns

Answer 20

dendritic
trellised
radial
centripetal

Question 21

define dendritic

Answer 21

resembles a tree
main river is a trunk
larger tributaries are branches and smaller tributaries form a pattern like branches and twigs
tributaries join the main river at acute angles
most common of all drainage patterns
occurs where there is uniform or homogenous rock type and a gentle slope

Question 22

define trellised drainage pattern

Answer 22

looks like a rectangular grid
often occurs in areas where there are alternating banks of resistant and less resistant rock at right angles to direction of slope
tends to occur in rocks heavily jointed and folded
main river flows across banks of rock following slope of land
tributaries able to erode banks of less resistant rock and join main river at right angles

Question 23

define radial drainage pattern

Answer 23

occurs when rivers radiate outwards from a central elevated point such as volcanoes and domes
resembles spokes of wheel or umbrella