Rivers

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What is a drainage basin?
An area of land that is drained by a river. They can be distinguished by the water sheds.
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What is a watershed?
An area of land drained by a river and its tributaries.
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What is a drainage basin hydrological cycle?
The part of the hydrological cycle that happens in a drainage basin. REMEMBER the DBHC is an open system whereas the hydrological cycle is a closed system.
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What is overland flow?
The movement of water over the surface of the ground to rivers.
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How is the water balance expressed?
P=O+E+/-S where P=Precipitation, O=Total runoff, E=Evaporation and S=Storage (in soil and rocks)
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What is the order of the hydrological cycle stages?
1.Evaporation 2.Evapotranspiration 3.Condensation 4.Precipitation 5.Surface runoff 6.Infiltration 7.Percolation 8.Ground water flow
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What is a Confluence?
Where a river splits into 2.
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Name 5 factors that can cause flooding.
Rainfall, vegetation (high or low amounts), geology, Soils, relief, urbanisation, basin shape and size and history.
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What is meant by the term 'lag time'?
The time between peak discharge and peak rainfall.
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What are the 3 river processes?
Erosion, Transportation and Deposition- All 3 are dependant on the rivers energy.
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What does a faster velocity create?
A greater turbulence. Water with a more turbulent flow can carry more sediment load.
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What factors affect velocity?
Channel shape in cross section, roughness of the channels beds and banks and the channels slope.
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What is a hydraulic radius?
The ratio between the cross section and the length of the wetted perimeter.
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How is the hydraulic radius calculated?
Cross sectional area/wetted perimeter.
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How do you calculate the corss section of a river?
Depth x length.
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What is a storm hydrograph?
A storm hydrograph is a graph where the river discharge (x axis) is plotted against time (y axis). It represents discharge during a storm or precipitation event. It shows the link between rainfall and river level.
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What does a storm hydrograph chart have to include?
Precipitation, Lag time, Baseflow, Rising Limb, Falling limb and Peak Discharge.
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What is the level of discharge before the storm called?
Antecedant discharge.
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Name three human factors affecting the shape and size of the storm hydrograph.
Size of the drainage basin, Shape of the drainage basin, Relief, Lenght of precipitation event, Intensity of precipitation, Permeability of rock type, Vegetation and Soil texture/structure.
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Name a physical factor affecting the shape and size of the storm hydrograph.
Urbanisation or deforestation
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What is meant by the term drainage density?
The length of the river channels in the drainage basin in relation to its size.
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What does base flow mean?
Normal river flow/discharge
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What are the 4 erosive processes?
Abbrasion, Attrition, Hydraulic action and solution
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Explain Abrasion
Abrasion- (corrasion) the material is being carried by the water wears away the bank and bed. it helps to cause lateral and vertical erosion. It also occurs when theres a high discharge
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Explain Attrition
Attrition- the river erodes the load by causing them to bump into each other so they become smaller and rounder.
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Explain Hydraulic action
The force of the water can dislodge material. Air bubbles are forced into cracks causing vibrations which resuts in the beds/banks weakening
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Explain solution
Solution- water can react with rocks such as limestone. The rate of reaction depends on the water acidity and temperature
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What are the 4 Transportation processes?
Traction, solution, saltation and suspension
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Which of the transportation processes bounces the material?
Traction
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Name the 3 types of load.
Bedload, Suspended load and Dissolved load.
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What does the hujlstrom curve show?
The velocity of water required for erosion, transportation and deposition of particles of different sizes.
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Is there always erosion in the river?
YES because the rivers always flowing.
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Is there always deposition?
NO because some things dont move or erode.
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What is the difference between the critical velocity line and the critical deposition line?
The critical velocity line indicates the velocity needed to pick up (erode) particles of different sizes. The critical deposition line shows the velocity below which particles of a particular size can no longer be carried and have to deposited.
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What are the 2 critical lines used for?
The split the graph into 3 sections; erosion, transportation and depostion.
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What does a river with a low flow look like?
The water is clear and the riverbed is visible.
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What does the amount of energy available in the river to do 'work' depend on?
The height the water has to decend, essentially gravity AND The amount or mass of water available
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How does potential energy turn to Kinetic energy?
A still body of water at any point above sea level has a certain amount of stored energy which is called potential energy. When the water starts to move downhill, the potential energy is turned into kinetic energy.
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What is Braiding?
A braided river is a river that has multiple channels and islands of sediment in between those channels. Yellow river, China.
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Where are braided rivers found?
They are found in Deltas, aeas where the the river channel banks are made of easily erodibe material or in areas of high sediment load where discharge varies.
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Where and how are meanders found/formed?
Meanders appear in the middle course of the river. They are formed by erosion and deposition. A meander is fromed when a river starts to undercut its bank on one side due to erosion, where materials is depositted on the othe side.
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Potholes
Potholes are round to oval shaped holes in the bedrock of a river bed. They are created where sediment accumilaes within naturally occuring small deppressions on the rock surface on the river bed. Gaping Gill, North Yorkshire, England.
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Whats a Delta?
A river delta is a landform that forms at the mouth of a river, where the river flows into an ocean, sea, estuary, lake, or reservoir. Deltas form from deposition of sediment carried by a river as the flow leaves its mouth.
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What is rapid?
A rapid is the part of a river which is fast and rough due to the steep gradient. they are a serious of short and fast falls and the river is usualy very shallow and runnign very fast over rocks.
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What did Bradshaw say would increase downstream?
Discharge, velocity, depth, width and load quantity.
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What did Bradshaw say would decrease downstream?
Load particle size, channel bed roughness and gradient
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What was Bradshaws theory?
That the rivers discharge, velocity, depth, width and load quantity would increase downstream.
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What was Bradshaws theory based on?
Schumms research and theory.
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What does competence mean?
The maximum size of load a river is capable of trasporting.
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What is headward erosion?
Erosion backwards or upstream above the original sorce, which recedes.
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Name 4 landforms of fluvial erosion and deposition
Valley in the upper, middle and lowere course, Potholes, waterfalls, levees,brading, rapids, meanders and oxbow lakes, deltas and flood plains.
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What method of primary data are we using in the exam?
Velocity using a hydroprop
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What are the 3 main components of a hydroprop?
Impellar, Thread and handle. (Impellar moves on the thread.)
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Name one human error that could happen when use the hydroprop
Standing in frnt of the hydroprop stopping the flow. Errors due to reaction times (clicking of the stopwatch)
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What does quantative mean?
Quantative is the numerical statistics
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What does qualitative mean?
Qualitative is opinion based data.
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State one technique you used to analyse your data and explain why you used it.
I used spearmans rank correlation co-efficient test to test the relationship between distance downstream and discharge/velocity/load size/angularity/depth/width/channel cross section area/wetted perimeter/hydraulic radius
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What does spearmans rank show?
spearmans rank shows the type of relationship, stregth and chance (significance)
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What is our signicant number for the spearmans rank correlation?
74-456
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What were our findings from the spearmands ranking?
Discharge- positive, weak, not significant. Depth- Positive, strong, significant. Velocity- Negative, weak, not significant. Width- positive, weak, not significant.
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Advantages of spearmans rank
Relatively quick, the coefficient itself shows whether a correlation exists and if so how strong.
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Limitations of spearmans rank
Places the values in numerical order and pays no regard to the magnitude of the differences betwen the values.
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An example of flooding in an MEDC
Carlisle, UK- 2005
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An example of fooding in an LEDC
Bangladesh, Asia- 1998
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Other cards in this set

Card 2

Front

What is a watershed?

Back

An area of land drained by a river and its tributaries.

Card 3

Front

What is a drainage basin hydrological cycle?

Back

Preview of the front of card 3

Card 4

Front

What is overland flow?

Back

Preview of the front of card 4

Card 5

Front

How is the water balance expressed?

Back

Preview of the front of card 5
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