hydrology and fluvial geomorphology Flashcards
(85 cards)
1
Q
What is the lithosphere
A
geological world
2
Q
What is biosphere
A
living world
3
Q
What is a drainage basin system
A
area of land drained by a river and its tributaries
4
Q
what is a watershed
A
boundary of a drainage basin (invisible land separating drainage basins) which is the highest contour of land surrounding a river or stream
5
Q
give an example of a drainage basin
A
Amazon basin covers 40% of South America and contains 1100 tributaries
6
Q
what is a dendritic drainage pattern
A
a tree like pattern where water may converge (meet) from a variety of directions before joining a main river channel
7
Q
what is a rectangular drainage pattern
A
where streams and channels follow geological weaknesses and gaps in blocky bedrock
8
Q
what is a radial drainage pattern
A
where water drains away from a central high point, hill or mountain into two separate channels
9
Q
what is a trellised drainage pattern
A
where streams follow slopes downhill and converge along areas or eroded rock
10
Q
what are endorheic drainage basins
A
inland basins that do not drain into an ocean so their base level is an inland lake or sea
11
Q
name an input of a drainage basin
A
precipitation which includes rainfall, snow, frost which is then stored or transferred in the system before its eventual output
12
Q
name an output of a drainage basin
A
evaporation, evapotranspiration and runoff
13
Q
what is storage in a drainage basin
A
parts of the system that hold or retain water for a period of time and can be open like on the surface of land or within vegetation or within rock structure
14
Q
name 2 stores in a drainage basin
A
interception, surface storage, soil moisture, channel store
15
Q
what is vegetation storage
A
when vegetation absorbs moisture directly through its root system and is stored within the plant or organism
16
Q
what is surface storage
A
where water is above the ground in the system and have a high rate of evapotransipiration
17
Q
what is channel storage
A
water that is contained within a river channel or stream at any given time
18
Q
what is groundwater storage
A
water that has become stored in the pores and spaces of underlying rocks
19
Q
what is an aquifer
A
where large quantities of underground waters are stored due to it being a water-bearing permeable rock or unconsolidated materials and can be found at any depth
20
Q
what is the overland flow transfer
A
the movement of waver river land downslope into a body of water
21
Q
what is the channel flow transfer
A
the movement of water within a defined channel such as a stream or river
22
Q
what is the percolation
A
the subsurface water that travels downward from the soil into the bedrock through the cracks and pores
23
Q
what is the transpiration output
A
the process of evaporation of water from plants through pores in their leaves
24
Q
what is river discharge
A
a measure of the volume of water moving in a river
25
how is river discharge influenced
the rate of precipitation and the speed at which water is transferred into the river
26
give the equation linking discharge, cross sectional area and velocity
Q=A x V
Q= discharge
A= cross sectional area
V= velocity
27
what do hydrographs do
enable us to look at the relationship between rainfall and discharge after each rainfall event as the river levels top up and subsequently drop over time
28
why is a rural area storm hydrograph flatter
more water is entering the river via throughflow and groundwater flow and less via surface-run-off. This has the effect of spreading out the flow over an extended period of time; hence the graph is flatter.
29
what is lag time
the period of time between the peak precipitation and the peak discharge
30
what is peak flow/ discharge
the maximum river discharge for any given event measured in cubic meters per second
31
what is rising limb
the part of the graph that initially rises indicating the increasing level of water as determined by the combined rate of surface runoff, through flow and groundwater flow followed by a precipitation event
32
what is storm flow
the additional discharge created as a result of a precipitation event
33
what is the falling limb
the part of the graph that shows the discharge decreasing and river levels falling back towards base level
34
what is catchment hydrology
the movement, distribution and quality of water within a drainage basin
35
what is infiltration rate
the flow of water through the soil surface into a pious medium under gravity action and pressure events
36
what are sedimentary rocks
formed through the deposition of sediment and the subsequent compression as additional layers are deposited above so water can pass through them so are permeable eg limestone
37
what are metamorphic rocks
sediments and rocks that have been transported by heat and pressure and the permeability depends on the transformation `
38
what are igneous rocks
formed by extreme gear and pressure in magmatic environments eg in volcanic situations
39
what is soil composed of
rock fragments, organic matter, water, air, organic material and organisms
40
the lesser the clay content the more water retentive the soil is- true or false
false the more content due to clay particles bonding together tightly which restricts the flow of water
41
Name 2 characteristics and processes of the upper course of a river
vertical erosion with hydraulic action, abrasion and attrition dominant processes, traction and saltation at high flow, load size is large and angular, v shaped valleys
42
Name 2 characteristics and processes of the middle course of a river
channel is deeper and wider, vertical erosion decreasing in importance and more lateral erosion and position, suspension is the main transportation type, load become smaller and less angular
43
Name 2 characteristics and processes of the lower course of a river
channel is at its widest and deepest and may be tidal, deposition is more important than erosion, fine material is deposited, large amount of load but the size is very small and rounded
44
what is laminar flow
is characterized by a smooth horizontal motion often too simplistic for complex natural river environments that have many changes, steps and gradients, can be found in carefully managed channelized sections on a relatively small scale where there are few additional influences
45
what is turbulent flow
is characterized by a series of erratic horizontal and vertical spiral flows that disturb the smooth appearance to the water and is the dominant flow in a river and it varies depending on the velocity of the flow as well as the influence of friction and the energy available after friction
46
what is helicoidal flow
a corkscrew like flow that is mainly found as water travels around river bends, it is associated with meanders and the formation of sediment bars and slip off slopes
47
what is hydraulic action as a form of erosion
the force of the water pushing into the cracks and hitting against the rivers banks which weakens the river bank causing erosion
48
what is abrasion as a form of erosion
sediment in the river is thrown or scraped along the banks of the bed of the river
49
what is attrition as a form of erosion
where stones and sediment within a river become increasingly rounded as they collide and break into smaller pieces
50
what is solution as a form of erosion
chemical process that occurs when water is slightly acidic and dissolves/ weakens certain types of rock
51
what is traction as a form of transportation
when the largest stones, boulders and cobbles are rolled along the riverbed by a stone turbulent flow in a bouncing action
52
what is salutation as a form of transportation
where smaller bedload such as pebbles, stones and gravel are lifted and carried temporarily in the flow in a hopping or bouncing motion
53
what is suspension as a form of transportation
where very fine particles of sand. and silt are carried in the last flowing water
54
what is solution as a form of transportation
where dissolved sediment and minerals are transported within the river
55
name 2 reasons why deposition may be more likely to occur
following low periods of precipitation where river levels drop, where the river flow meets the sea, in areas of slow flow within a channel such as meander bends, when the load suddenly increases above the capacity eg a landslide when the water has carried the material outside of the channel eg in times of flood
56
what does the Hjulstorm's curve show
the relationship between particle size and velocity
57
what is the mean call or settling velocity curve
shows the velocities at which particles of a given size become too heavy to be transported and so will fall out of suspension and be deposited
58
what is one of the three features of the Hjulstrom's curve
the smallest and largest particles require high velocities to lift them, higher velocities are required for entrainment than for transport, when velocity falls below a certain level those particles are deposited
59
how are v-shaped valleys formed
large angular boulders often choke the upper channel creating more friction and disrupting flow. During peak discharge vertical erosion will be high as there is a greater capacity for erosion. Though the generalized image of a V is common the extent of the angle of incision will be dependent on local factors such as rock type
60
how are interlocking spurs formed
as the river flows downstream it may be forced to wind through the landscape creating protrusions of the riverbank in the valley known as spurs. As the river continues to wind downstream in a zig zag pattern the view along the course of the river may be restricted as the spurs appear to knit together like clasped fingers.
61
how are rapids and pools formed
rapids are areas of high velocity turbulent flow. They are created by sudden change in gradient or a narrowing of the river. Contrastingly the pools are areas of slow moving deep water that have low erosive capability and greater deposition.
62
explain how the formation of waterfalls leads to plunge pools and deep sided gorges
waterfalls are large steps in the river as a result of differential erosion usually attributed to bands of hard and soft rocks. Water flowing over hard rock will have relatively little impact erosively. Once it then meets a band of softer rock there will be greater erosion. Over time the amount of erosion will be so great that a noticeable step in the profile may be created. Continued erosion may cause undercutting of the rock layers eventually resulting in rock collapse. The fallen material is often large and angular and is forced to swirl around sourcing out a depression known as a plunge pool. As the process is repeated waterfalls migrate upstream leaving a deep steep sided gorge
63
how are meanders formed
meanders are created as the result of both erosion and deposition. Meanders have an asymmetric cross section. On the outside of the bend where the flow is the fastest erosion deepens the channel. On the inside of the bend where the flow is slower deposition occurs. Helicidial flow occurs where surface water flows towards the outer banks while the bottom flow is towards the inner bank Variations in the flow create differences in the river cross sections.
64
how are river cliffs formed
River cliffs are formed on the outside of the bend where erosion is greatest. The combined effect of hydraulic action and abrasion weaken the riverbank causing it to collapse. Over time a steep bank will be formed with some of the collapsed material remaining on the riverbed
65
what happens to meanders over time
meanders constantly change and evolve. As continued erosion occurs the river cliff will migrate back as deposition on the inside becomes more stabilized leading to the movement of the river across the landscape. Meander bends become more pronounced so the path of the river no longer becomes the most efficient route. The river may continue to erode the outside of the bend before eroding a shortcut between meander bends causing temporary shortening of the channel. Where this occurs the bend may become eventually redundant. Isolated bends will become detached creating oxbow lakes due to its lack of fluvial input it will Stu ip.
66
what is a floodplain
large areas of flat land surrounding a river channel. They are the areas most susceptible to flooding. Initially cut by a river a floodplain is made up of a large amount of alluvial deposits dropped during times of flood. As a result they are often fertile and good for agriculture.
67
what is a bluff
the edge of the floodplain marked by a slightly raised line
68
how are levees formed
when a river floods its banks the corsets material is often deposited first creating a ridge along the edge of the river channel. Over time more sediment may be added to the ridge thus creating a natural preventative barrier to flooding
69
what is braiding
occurs when there is a high proportion of load in relation to the discharge. At time of low flow the river may be forced to cut a series of paths that converge and diverge as they weave through large expanses of deposited material. It begins at the mid channel bar that grows downstream as the discharge decreases following a flood. The coarse bed-load is deposited first
70
how are deltas formed
when large amounts of river load meet the sea and are deposited. They are composed of fine sediments that are dropped with low energy. They are triangular in shape. As freshwater and saltwater mix, clay particles stick together and settle to the sea bed in flocculation. The finest sediments are carried the furthest and are first to be deposited
71
what is the hydrological cycle
the continuous circulation of water within the Earth's hydrosphere, and is driven by solar radiation.
72
what do humans require water for
agriculture, energy production, navigation, recreation and manufacturing
73
in the last 30 years how much has the earths temperature increased
0.8 degrees celcius
74
how does precipitation occur
water vapor must attach to small particulate matter in the atmosphere known as hygroscopic nuclei. As the water vapor accumulates and condenses to form clouds the water increases in size before falling under the influence of gravity
75
how does urbanization increase flood risk
urbanization means there are more impenetrable surfaces which lead to water being carried along quicker and reaching rivers quicker. This raises the levels of the river and increases surface runoff in urban areas.
76
how much of Britain is covered by natural woodland
less than 1%
77
how does deforestation lead to flooding
deforestation reduces evapotranspiration rates and increases surface runoff so the lag time is decreased.
78
describe how afforested areas can help flood management and habitat creation
afforested areas have a greater capacity to absorb moisture which binds the soil. They are largely covered which increases infiltration and can help to reduce lag time and create new habitats
79
how can humans impact dams and reservoirs
large stores of open water such as reservoirs increase the potential for evaporation so water loss can be due to industry and larger amounts of large water stores
80
what is water abstraction
the removal of water either temporarily or permentantly from lakes river canals. The redirection of this water from the natural flows within a drainage basin can be down for commercial industrial or domestic purposes.
81
what is irrigation
used to increase the productivity of an area through water redirection though the amount of water must be carefully managed to suit the crop.
82
what is groundwater withdrawal.
the process of extracting groundwater from the aquifer.
83
how can we predict floods
Much of modern flow prediction utilizes technology and relies on computer models and simulation software that use algorithms based on the characteristics of an area. The use of precipitation data as well relief, land use and saturation rates may all be used to help forecast the flow rates
84
give 3 examples of hard engineering
dams, channelization, levees, storm drains, culverts, barrages
85
define soft engineering
follows a more sensitive approach to maintain and control river flow. It utilizes the natural environment where possible and use of the natural and local materials to modify the river whilst still maintaining its character
