GEOMORPHOLOGY OF RUNNING WATAER

Question 1

Most important agent of landscape formation

Answer 1

water

other factors may be locally dominant

Question 2

distribution of earth’s water

Answer 2

fresh water = 3%

saline = 97%

Question 3

distribution of fresh water

Answer 3

ice-caps and glaciers= 68.7%
ground water = 30.1%
other = 0.9%
surface water = 0.3%

Question 4

distribution of surface water

Answer 4

rivers = 2%
swamps = 11%
lakes = 87%

Question 5

why does the total amount if water on earth’s surface stay constant?

Answer 5

due to processes associated with the hydrological cycle

Question 6

what are the interconnected elements of the hydrological cycle?

Answer 6

• precipitation
• interception
• evaporation
• evapotranspiration
• filtration/percolation
• surface runoff
• ground water

Question 7

precipitation

Answer 7

clouds form due to ascent of saturated air parcel and associated cooling
Rain/snow results from coalescence of cloud water droplets.
Fog/mist is the same, except that the cooled air is found close to ground surface

Question 8

spatial variation

Answer 8

Distribution and intensity of rain is highly variable, e.g. rain shadow; high spatial variability

areas in the rain shadow (it rains on one side of the mountain and the water cant pass to the other side of the mountain) are often very dry

Question 9

spatial vaiability

Answer 9

means that some places get more rainfall than others

Question 10

temporal variability

Answer 10

differences over time
short-term variab
seasonality
long term variab

Question 11

intensity of precipitation

Answer 11

can also be variable

how much precip falls in a set amount of time??

Question 12

intensity of precipitation

Answer 12

can also be variable

how much precip falls in a set amount of time??

Question 13

precip variability in arid regions

Answer 13

lower precip
more variable precip
less reliable precip

Question 14

interception

Answer 14

• rain doesnt always fall directly on the grounf

- vegetation cover - precip is intercepted by plant foliage

Question 15

geomorph importance of interception by foliage?

Answer 15

vegetation protects the land surface from direct impact of rainfall - reduces raindrop impact

vegetation also protects the soil through the binding action of plant roots

Question 16

evaporation

Answer 16

-causes the huge difference between precip inputs and outputs along with transpiration (evap - storage and trans - comsumption)

Question 17

evapotranspiration

Answer 17

accounts for 84% of precip in Africa

Question 18

runoff ratio/ co-eff

Answer 18

ratio of total rainfall to total runoff in a catchment

low in semi arid seasonal rainfall climates such as across large areas of southern africa

Question 19

Infiltration

Answer 19

depending on rainfall intensity and the nature of soil some precip enters soil by infiltration

Question 20

what is infiltration capacity

Answer 20

maximum rate of absoption – if this is exceeded then surface water runoff happens

Question 21

what factors influence infiltration capacity

Answer 21

soil conditions and land-use
-coarse vs fine grained soil
-heavy used land
less permeable surfaces - outcome may be erosion and transport of material

Question 22

what happens to water that doesnt evap or runoff

Answer 22

infiltrates/percolates downwards to become groundwater

Question 23

groundwater

Answer 23

precipitation that passes from soil later into underlying bedrock and meets zone of saturation (surface of which is referred to as the water table)

Question 24

ground water variability

Answer 24

water table follows the general shape of surface topography

water table follows the general shape of surface topography

Question 25

original ideas about runoff

Answer 25

American hydrologist: RE Horton overland flow occurs on a slope in response to precipitation intensities that exceed infiltration capacity

Question 26

Hortonian overland flow

Answer 26

(infiltration excess overland) flow envisaged to occur across the landscapeand be main cause of the rapid rise of river levels during storms

Question 27

problems with hortonian flow model

Answer 27

1) surface runoff is rarely simultaneously widespread in the landscape 2) rainfall intensities do not always exceed infiltration capacity even during severe storms

Question 28

additional mechanism to explain how runoff occurs

Answer 28

saturation overland flow

Question 29

difference between hort and sat flow

Answer 29

hort = rainfall intensity is the initiating factor sat = rainfall duration is the initiating factor

Question 30

interflow/through flow

Answer 30

lateral movement of water within soil that may produce pipes or even tunnels which transmit water at considerable speed

Question 31

movement of water on slopes is a combination of flow types

Answer 31

hortonian overland flow saturation overland flow through flow ground water flow ultimate destination - channel/river

Question 32

what is water measured as once in rivers?

Answer 32

discharge | the volume of water flowing through the stream per unit time

Question 33

extreme discharge -

Answer 33

flood

Question 34

changes in discharge over time are recorded on a ...

Answer 34

flood hydrograph

Question 35

discharge formula

Answer 35

cross-sectional area x velocity Q

Question 36

what is the flood hydrograph?

Answer 36

record of changes of discharge over time

Question 37

what causes variation is flood hydrograph shape

Answer 37

conditions in the catchment

Question 38

why do different surfaces have different infiltration capacities?

Answer 38

differences in interception (evaporation) and infiltration

Question 39

what to consider when looking at contrasting flood hydrogr

Answer 39

natural vegtation vs agricultural vs urbanisation

Question 40

different graphs flood hydros

Answer 40

size of drainage basin -- small vs large vegetation -- bare vs forest valley side steepness -- steep vs gentle soil type -- impermeable vs permeable

Question 41

what processes of water do geomorph work in channels

Answer 41

erosion transport deposition

Question 42

erosion

Answer 42

after weathering running water erodes rock --abrasion --undercutting stream ability to erose is dependent on type of flow

Question 43

types of stream flow

Answer 43

laminar | turbulent

Question 44

entrainment

Answer 44

once eroded material is transported in the direction of flow

Question 45

types of transport in a stream

Answer 45

in solution suspended load bedload

Question 46

saltation

Answer 46

jumping of particles

Question 47

bedload

Answer 47

carried along stream bottom

Question 48

suspended load

Answer 48

carried either in suspension or by saltation

Question 49

solution transport

Answer 49

sediment is dissolved in stream water and carried along steam in solution

Question 50

competence of a stream

Answer 50

ability of a stream to transport sediment

Question 51

what is stream competence dependent on

Answer 51

velocity of flow volume of flow periodicity of flow periodicity of flow

Question 52

what results in deposition

Answer 52

loss of stream competence

Question 53

what causes loss in stream competence?

Answer 53

changes in discharge | change in gradient of river bed

Question 54

what does a Hjulstrom diagram depict?

Answer 54

relationship between erosion, transport and deposition

Question 55

zones of a drainage basin and dominant processes

Answer 55

erosion - headwaters transport - middle reaches deposition - lower reaches - floodplains and deltas

Question 56

what does the nature of relationship between particle size and velocity of flow determine

Answer 56

whether a particle will be eroded, transported or deposited

Question 57

Hjulstrom diagram parameters

Answer 57

x axis = grain size y ax = stream velocity headings top x axis - fine particles - coarser particles

Question 58

why is a greater velocity needed for fine particles?

Answer 58

clump together and form a relatively large mass

Question 59

what are three human processes that impact the environment (fluvial systems)

Answer 59

land use changes urbanization dam construction

Question 60

what are the impacts on fluvial systems by three human processes

Answer 60

hydrolog cycle is modified - -discharge - -channel form - -sediment load

Question 61

changes in streams following landuse changes...

Answer 61

in annual and seasonal discharge (may be positive or negative) e.g. in fynbos catchments the effect of a change from fynbos to forest plantation (increased biomass) is to reduce runoff --flood characteristics (increases or decreases) --water quality e.g. fertilizers -- erosion (increases)

Question 62

effects of dam construction (check written notes for better explanation)

Answer 62

Decreased sediment load downstream of the impoundment results in ‘clearwater erosion’ (i.e. incision of stream below dam wall due to increased competence) Decreased sediment supply to the coast impacts beach and dune systems (sediment ‘starvation’) Shrinking deltas and accelerated relative sea level rise Mass of water as well as increased pore water pressures in underlying geology may increase risk of slope failure (e.g. Vaiont, Chinese examples)