Hydrology and fluvial geomorphology

?
What is a drainage basin
A drainage basin system is an open system as water can be added as an input or lost as an output
1 of 112
What is evaporation
The loss of water from the land surface and bodies of water as it transfers from a liquid to a gaseous state (water vapour) The higher temperature the higher the rate of evaporation
2 of 112
What is evapotranspiration
The combined loss from both evaporation and transpiration
3 of 112
What is transpiration
The loss of water vapour from the stomata in leaves of plants and trees. Rates of transpiration depend on amount and type of vegetation
4 of 112
What is river discharge
The volume of water being discharged by a river. It is normally expressed as the volume of water passing a point in the river channel in a given unit of time This is commonly the number of cubic metres per second (cumecs)
5 of 112
What is a store
Where water is held in some part of the drainage basin for any length of time(leaf, puddles, soil, lakes)
6 of 112
What is a soil store
Water within pore spaces of the soil (interstices)
7 of 112
What is a groundwater store
water percolated and held in rocks below the top of the water table
8 of 112
What is interception
precipitation intercepted on its way to the land surface (by plants, leaves and trees)
9 of 112
What is interception stores
Plants, leaves, trees etc
10 of 112
What is depression stores
Water stored on the surface (puddles, ponds, streams and lakes
11 of 112
Where are depression stores usually found
Above an impermeable surface or when ground or soil or ground below is fully saturated
12 of 112
What is an input
Input = addition of water to a drainage basin - precipitation - (rain, snow, hail etc)
13 of 112
What is an output
Losses of water from drainage basin (evaporation, evapotranspiration, river/channel flow)
14 of 112
What is a soil moisture store
Water retained within gaps and pore space in the soil
15 of 112
What is antecedent moisture
antecedent moisture is the moisture retained in the soil before a rainfall event
16 of 112
What is a groundwater store
Water that percolated downwards and held in gaps(cracks, joints, bedding planes, fault lines and pore spaces in rocks in underground aquifer
17 of 112
What is an aquifer
Underground layer of water bearing rock e.g. sedimentary(sandstone)
18 of 112
Factors that influence amount of water that reaches the groundwater store
Precipitation amount and intensity, surface flow and throughflow
19 of 112
What is throughfall
Precipitation direct to land surface without interception
20 of 112
What is dripflow
Precipitation intercepted by leaves
21 of 112
What is stemflow
Flow of water down stems of plants from Precipitation(If larger trees water flows down trunks (trunk flow)
22 of 112
What are the impacts of stemflow
Precipitation released slowly to the land surface allowing it to slowly infiltrate
23 of 112
What is overland flow
Water flows over land surface
24 of 112
What is channel flow(form of overland flow)
Water flows in small channels, rills which are less than 30cm in width/depth in a defined stream/river channel
25 of 112
What is sheet flow(form of overland flow)
Rare event where layer/sheet of water on the ground surface
26 of 112
When would sheet flow occur
Excess overland flow(no infiltration e.g. rainfall intensity exceeds infiltration capacity on surface + Impermeable soils e.g. clay reach infiltration capacity therefore there is saturation overland flow
27 of 112
What is infiltration
Water entry into the surface of the soil
28 of 112
What is infiltration capacity
Rainfall intensity exceeds infiltration capacity of the surface
29 of 112
What is percolation
Downward movement of infiltrated water through pores and spaces of soil
30 of 112
What is porosity
Number of open pore spaces in soil/rock e.g. chalk is porous
31 of 112
What is permeabiliity
Size and number of cracks, fault lines, joints and bedding plantes in the rock
32 of 112
What is throughflow
lateral movement in soil of infiltrated water
33 of 112
What is baseflow
Baseflow(groundwater flow) - water infiltrated and percolated into bed rock below the soil moving laterally.
34 of 112
Label diagram of flows
f
35 of 112
What are water tables
The top of the saturated zone once percolation has reached full infiltration capacity
36 of 112
What will the height of the water table depend on
Season(winter or summer/ wet or dry)
37 of 112
When does the recharge of groundwater take place
When precipitation on the land surface exceeds evapotranspiration and water infiltrates ground and percolates down to the aquifer
38 of 112
What does an annual hydrograph show(diagram)
Patter of seasonal variation that takes place to a river's discharge in a typical year.
39 of 112
What is a storm hydrograph
shows river discharge after a rainfall event
40 of 112
What are the key components of a storm hydrograph
Lag time between rainfall peak and flood discharge peak which show how quickly precipitation is reaching the river channel after rainfall event
41 of 112
What does a storm hydrograph show
importance of quick flows and the baseflow/groundwater flow
42 of 112
What is rainfall peak(hydrograph)
The highest amount of rainfall during a rainfall event(usually the median of the event)
43 of 112
What is peak discharge (hydrograph)
Peak discharge/peak flow - highest amount of discharge
44 of 112
What is lag time (hydrograph)
Time between rainfall peak and peak discharge
45 of 112
What does rising/ascending limb show(hydrograph)
discharge rising from start of rainfall event until reaching peak discharge
46 of 112
What does falling/recession limb show (hydrograph)
Discharge falling
47 of 112
Label hydrograph
f
48 of 112
What is an approach segment
Time before water from rainfall event gets into the river
49 of 112
What is a bankfull discharge
Discharge of the river at the top of the river banks(any more will cause the river to flood the surrounding floodplain
50 of 112
List the flows in order of speed of arrival
1) overland flow/surface runoff 2) throughflow 3) baseflow/ groundwater flow
51 of 112
What might influence a hydrograph
Precipitation, intensity, temperature and evapotranspiration
52 of 112
How does precipitation type impact the discharge of the river
Rain will discharge very quickly whereas snow will be a delay discharge and will be released into the river over time as oppose to rain
53 of 112
How does precipitation intensity impact the discharge of the river
When precipitation intensity exceeds infiltration capacity of the soil or surface surface runoff will result. Therefore water reaches river channel rapidly increasing discharge and potentially flooding
54 of 112
How does climate impact the discharge of a river
River in equatorial climate has constant annual precipitation therefore consistent discharge. However a river experiencing wet and dry seasons will have varying river discharge. sub zero = very little through winter. Large in summer (Ice/snow melts)
55 of 112
How does antecedent moisture impact the discharge of a river
The level of antecedent moisture will determine the level of infiltration capacity. e.g. higher antecedent moisture the lesser infiltration capacity
56 of 112
What are the characteristics ofa drainage basin
larger drainage basin = more water collected 2) Large drainage basins e.g. Nile, Mississippi during heavy rainfall only one part will be effected
57 of 112
What is drainage density
High drainage density = water reaches river and stream channels quickly as water travels short distance to river channel- produces flashy hydrographs(short lag time, sharp flood peaks. Low drainage density = delayed hydrograph (opposite to flashy)
58 of 112
What effects porosity and permeability of soils
soil type(infiltration rate)(clay = slow as very tiny pore spaces/sandy = fast as large pore spaces
59 of 112
How does rock type effect permeability and porosity
Limestone and chalk store more precipitation and release it more gradually as baseflow/groundwater flow. Impermeable rocks e.g. sedimentary rocks-clay, igneous granite and metamorphic schists do not absorb as much water therefore surface runoff high
60 of 112
How do slopes effect infiltration
Steep slopes = greater overland flow/surface runoff Gentle slopes = higher infiltration rates as longer on slope
61 of 112
how does vegetation type effect infiltration
Encourages greater interception and infiltration as slows water down through types of interception
62 of 112
How does land use effect infiltration
removal and storage water can lower water tables reducing baseflow 2)replacement of woodland with permanent pasture leads to reduces interception and soil compacted therefore overland flow more common 3) Impermeable surfaces of concrete, roofs,
63 of 112
How do you increase the level of infiltration
afforestation decreases overland flow through interception
64 of 112
What are the differences between natural forest hydrograph and a permanent pasture hydrograph
Pic on phone
65 of 112
What is erosion
Picking up and removal of material
66 of 112
What is abbrasion (river)
rocks/rock fragments from channel floor are thrown against side of river by force of the flow
67 of 112
What is the process of evorsion(river)
Some bedload trapped in depressions in the bed of the channel and spin round by the current. FORMS potholes which enlarge and merge and contribute to deepening/lowering of the channel bed
68 of 112
What is Solution (river)
When acids in river water put certain minerals in solution. EFFECT against limestone, chalk
69 of 112
What is Cavitation (river)
turbulent flow when water is full of air bubbles e.g. plunge pools below waterfalls. Bubbles implode and create small cavities in the rock of the channel bed and sides
70 of 112
What is hydraulic action
Force of the river against banks cause air to be trapped in cracks. Pressure weakens the banks and gradually wears it away
71 of 112
What are the different processes of transport (river)
pic on phone
72 of 112
What is suspension (river transport)
Fine material e.g.clay and sediment carried by the river
73 of 112
What is solution (river transport)
Disolved minerals carried by the river
74 of 112
What is traction (river transport)
Large boulders and pebbles rolled along the river bed
75 of 112
What is saltation (river transport)
Small stones, pebble and silt bounces along the river bed
76 of 112
Describe a Hjülstrom curve
pic on phone
77 of 112
What factors influence river velocity
The gradient of the channel bed 2) The volume of water in the channel 3) The shape of water in the channel 4) Channel roughness (friction acting on water slowing it down)
78 of 112
Manning equation for river discharge = Discharge in cubic metres per second (CUMECS)
Channel cross sectional area, in square metres x velocity, in metres per second
79 of 112
What is Laminar flow
found in smooth, shallow, straight channels with a slow velocity (usually in sheets sliding over one another parallel to the river bed. USUALLY FOUND IN LOWER SECTION of river course
80 of 112
What is Turbulent flow
Found in rough, shallow channels , complex and rapid changes in shape and an increased velocity. Produce spinning eddies and trap air bubbles (white water effect)
81 of 112
What is Helicoidal flow
Happens during meandering where top of water surface from inside bank moves toward outside bank where it drops toward the bed
82 of 112
What is a Thalweg
The maximum depth and maximum velocity found in a river channel. Flows from outside of meander bends
83 of 112
What causes straight channels in nature
Low energy 2) Small discharges 3) Gentle gradients
84 of 112
How is a meander formed
Pic on phone needs annotation
85 of 112
How are braided channels formed
Pic on phone needs annotation
86 of 112
Under what conditions do braided channels occur
Abundant amounts of bedload, easily eroded banks, high and variable discharges, steep long gradients/channel slopes
87 of 112
What are the features of a meander
Pic on phone
88 of 112
how are river cliffs formed
Water flows fastest on the outer bend of the river. Causes lateral erosion of the bank where it undercuts the river bank
89 of 112
how are point bars formed
Increased friction on inside of meander results in deposition and sediment is dropped causing a bar to be created
90 of 112
What is a riffle
Accumulation of fluvial sediment which forms bar. Then further sand and gravel on the bed of the river channel causes bed to be shallow and rough
91 of 112
What is a pool
Deeper area with laminar flow-Found where erosion is greatest and deeper such as outside of deeper meandering bends
92 of 112
What are the three conditions under which a waterfall is formed
A layer of resistant rock passing across the bed of a river channel-causing differential erosion 2)A drop in base level caused by rejuvenation of the river channel 3)Earth movement-Triggered by earthquake producing a fault line-drop in river
93 of 112
Describe a waterfall
Pic on phone
94 of 112
How are rapids formed
When a waterfall retreats the waterfall becomes smaller in size until it disappears producing steeper, more turbulent section of a river, often with a rough bed
95 of 112
Features of a floodplain
Floodplains are the the catchment area when flooding takes place. located in lower river profile with gentle gradients. Floodplains are edged by bluffs. When river reaches bankfull level water is added to the river and becomes overbank flow
96 of 112
What is a bluff(river)
Formed by river erosion on the outside of the meander
97 of 112
What are the effects of regular flooding
build up of nutrient rich alluvium(silt) which forms a flat and fertile floodplain
98 of 112
What is a levée (river)
Parallel to the river on the edge of the floodplain. Reaches the river channel. Lies slightly above the level of the rest of the floodplain. Formed during flooding by deposition of heavier sediments as floodwater exits river channel
99 of 112
What is a delta(river)
Fan shaped feature formed when vast quantities of sediment are deposited at the mouth of the river when reaching sea/lake. Deposited due to slowing of the river.
100 of 112
What is flocculation(river)
Salts in sea water join fine slay brought down by river have a chemical reaction and forms larger heavier particles which fall to sea bed
101 of 112
What are the distributaries of a delta
Arcuate-Many distributaries, fan shaped and uniform shape Digital(bird foot)-vast amounts of load split into two or more channels which deposit load on sides and into sea Cuspate-form a pointed delta shaped by tidal and longshore currents
102 of 112
What are the modifications to a catchment flow and stores to channel flows by land-use changes
Deforestation-reduce interception among other flows2)Afforestation opposite affect to deforestation3)Urbanisation-Increase flows into a river channel as impermeable surfaces4)Water abstraction-water removed from aquifers causes drop in water table
103 of 112
What are causes of floods
excessive inputs of precipitation into river basin-often flooding during hurricane/cyclone events as in Bangladesh2)human activities influence overland flow, deforestation and urbanisation
104 of 112
What percent of global floods accounted for the 9632 in 20th century
31 percent
105 of 112
What damage can flooding cause
Damage to ecosystem, land , water quality and increased incidence of waterborne diseases(cholera)
106 of 112
How can you predict flood risk
Analysing flood recurrence intervals(10,50,100,500) year events2)Catchment modelling of sections of the river shows recurrence interval, frequency and magnitude
107 of 112
Example of a 1 in 100 year event
Cumbria in North West England in Nov 2009 and Dec 2015- Both received record rainfall over a 24 hour period 2009=316mm 2015=341
108 of 112
How are forecasts and warnings carried out
Flood forecasting using satellite imagery, rainfall radar, rain gauges and discharge recorders in the upper part of river 2)Satellite imagery updated every 15 mins shows approaching weather systems
109 of 112
What are some methods of hard engineering(flooding)
Dams e.g. Three gorges dam on Yangtze river used to regulate flow 2)Straightening of river channel can speed up flow of flood water 3)Artificial levées,flood walls and embankments, Diversion spillways E.G. The river exe
110 of 112
What are some methods of soft engineering(flooding)
Floodplain and drainage management, wetland and river bank conservation and river restoration Afforestation/reafforestation, Changing farming practices(terracing, contour ploughing, cover crops, Floodplain retreat EG Mississippi buying land
111 of 112
What is an example of flooding
Write it
112 of 112

Other cards in this set

Card 2

Front

What is evaporation

Back

The loss of water from the land surface and bodies of water as it transfers from a liquid to a gaseous state (water vapour) The higher temperature the higher the rate of evaporation

Card 3

Front

What is evapotranspiration

Back

Preview of the front of card 3

Card 4

Front

What is transpiration

Back

Preview of the front of card 4

Card 5

Front

What is river discharge

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Geography resources:

See all Geography resources »See all Hydrology and fluvial gemorphology resources »