Hydrology and Fluvial Geomorphology

Question 1

Stem flow

Answer 1

water running down a plant stem or the trunk of a tree

Question 2

Soil moisture

Answer 2

water stored in the soil

Question 3

Transpiration

Answer 3

a process by which plants return moisture to the atmosphere, having taken it up though their roots

Question 4

Groundwater store

Answer 4

a store of water held below the surface in the ground zone, above the base rock

Question 5

Surface store

Answer 5

water held on the surface in lakes, ponds and puddles

Question 6

Interception

Answer 6

where some precipitation is temporarily caught by plant leaves before reaching the ground

Question 7

Groundwater flow

Answer 7

the down slope movement of water through underlying rocks or the downhill transfer of water through pores and small cavities in the soil/ rock, depending on the rock type

Question 8

Aquifer

Answer 8

an underground layer of permeable rock, sediment or soil that yields water

Question 9

Throughfall

Answer 9

water falls off leaves onto the ground surface, or falls through gaps in the vegetation

Question 10

Field capacity

Answer 10

the amount of water that the soil is able to hold when it is fully saturated

Question 11

Catchment area

Answer 11

the area within a drainage basin

Question 12

PEVT

Answer 12

the water loss that would occur if there was an unlimited supply of water in the soil for use by vegetation

Question 13

Interception loss

Answer 13

water retained by plant or or surfaces that is later absorbed or evaporated

Question 14

Soil moisture deficit

Answer 14

the degree to which the soil moisture levels fall below field capacity

Question 15

Soil moisture recharge

Answer 15

precipitation exceeds PEVT, so there is some filling up of water in the dried-up pores

Question 16

Soil moisture utalisation

Answer 16

water is drawn to the surface by capillary action

Question 17

Porosity

Answer 17

the capability of the rock to hold water

Question 18

river rejuvenation

Answer 18

a period of vertical erosion to achieve a new, lower base level, enabling the river to achieve its desired concave shape

Question 19

eustatic change

Answer 19

global rise and fall of sea levels

Question 20

isostatic change

Answer 20

the local adjustment of land levels

Question 21

river capture

Answer 21

when a river cuts backwards over time due to head ward erosion and captures tributaries of another river

Question 22

alluvium deposition

Answer 22

sediment that is deposited that was once suspended

Question 23

river regime

Answer 23

hydrograph showing river discharge over a year

Question 24

drainage density

Answer 24

number of tributaries per km2

Question 25

bankfull discharge

Answer 25

maximum discharge a river can hold before it goes into flood

Question 26

saturated overland flow

Answer 26

soil has reached field capacity so no more water can be absorbed resulting in overland flow

Question 27

hortonian flow

Answer 27

when the ground is hard after a period of dry weather, so infiltration cannot take place, resulting in overland flow

Question 28

clear-water erosion

Answer 28

erosion caused by the action of the water

Question 29

antecedent rainfall

Answer 29

rainfall that has occurred previous to a weather event

Question 30

alluvial fan

Answer 30

triangular shaped deposits of water-transported material

Question 31

lag time

Answer 31

time between peak rainfall and peak discharge

Question 32

centre-pivot irrigation schemes

Answer 32

crops are irrigated by sprinklers which rotate around a centre pivot

Question 33

long profile

Answer 33

a graph drawn along the course of the river from source to mouth showing the change in altitude

Question 34

knick point

Answer 34

a steep region along the river profile which disrupts the ideal concave shape

Question 35

flocculation

Answer 35

when particles clump together (especially clay bonding along its flat edge)

Question 36

thalwag

Answer 36

the path of least resistance where the water is flowing that fastest

Question 37

mean fall/settling velocity curve

Answer 37

represents the average velocity at which sediment of a certain size will no longer be transported and will instead be deposited

Question 38

mean critical erosion velocity curve

Answer 38

average velocity at which a river is able to entertain (pick up) sediment of a particular size

Question 39

turbulent flow

Answer 39

flow over rough beds

Question 40

bification

Answer 40

flow over rough beds

Question 41

eyot

Answer 41

small island in a river

Question 42

helicoidal flow

Answer 42

the cork-screw-like flow of water in a meander

Question 43

wetted perimeter

Answer 43

the perimeter of the cross sectional area of the river that is 'wet'

Question 44

hydraulic radius

Answer 44

the cross sectional area / wetted perimeter -- a measure of efficiency - high HR = more efficient

Question 45

abrasion

Answer 45

the erosion of the bed and banks by the load carried

Question 46

attrition

Answer 46

the erosion of the load being carried, producing smaller, rounded particles

Question 47

hydraulic action

Answer 47

force of air and water on the sides of the river and in cracks

Question 48

solution (erosion)

Answer 48

the erosion of the bed and banks by chemicals in the water

Question 49

solution (transport)

Answer 49

minerals dissolved in the water

Question 50

suspension

Answer 50

smallest particles carried above the riverbed by the current

Question 51

saltation

Answer 51

small particles move along the riverbed in t a series of 'bounces'

Question 52

traction

Answer 52

pebbles pushed along the riverbed by the current

Question 53

competence

Answer 53

the diameter of the largest particle that can be carried by a river

Question 54

capacity

Answer 54

largest amount of load that a river can carry

Question 55

turbulent flow

Answer 55

where there are higher velocities and an increase in bed roughness - associated with hydraulic action

Question 56

laminar flow

Answer 56

smooth, straight channel with low velocity, allows water to flow in sheets parallel to the channel bed

Question 57

bluff

Answer 57

another word for river cliff but also used to describe the edge of a river terrace

Question 58

hydrological cycle

Answer 58

the cycle of water between atmosphere, lithosphere and biosphere

Question 59

percolation

Answer 59

the downwards movement of water from the soil into the bedrock

Question 60

throughflow

Answer 60

the flow of water through the soil through percolines

Question 61

baseflow

Answer 61

the part of the river discharge provided by groundwater seeping into the riverbed

Question 62

spring

Answer 62

natural flow of water from the earths surface, occurring when the water table occurs at the surface