RIVERS Revision Booklet

AS LEVEL GEOGRAPHY

Checklist:

I can

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Draw and label a drainage basin

Explain what each of the flows and processes are (e.g., infiltration)

Describe and explain a water balance graph

Label a storm hydrograph

Explain physical and human characteristics that influence the shape of a hydrograph

Describe the four types of fluvial erosion

Describe the four types of fluvial deposition

Explain the difference between capacity and competence

Explain what a Hjulstrom Curve shows

Name the features found along the long profile of a river. I also can name a river case study which shows these features

Explain how a channels characteristics varies downstream (e.g., hydraulic radius, wetted perimeter)

Draw and label the change in cross-profile of a channel and valley along its long profile.

Explain the formation of waterfalls, potholes and rapids

Explain the formation of meanders, flood plains, levees and ox-bow lakes

Explain the formation of deltas, braiding and distributaries

Explain the causes of river rejuvenation and its associated landforms

Explain the physical and human causes of flooding and relate this to a case study

Explain the social, environmental and economic impacts of flooding and relate this to a case study

Can compare the causes and impacts of flooding between LEDC and MEDC case studies

Explain how flood frequency can be calculated

Describe and give examples (case studies) of hard engineering strategies

Describe and give examples (case studies) of soft engineering strategies

Compare the relative merits of hard and soft engineering strategies

(Quick facts:A river drainage basin is __________________________________________________________________________________________________________________________________________________________The watershed is _______________________________________________________________________________________________________________________________________________________________)

(In the box above draw a typical drainage basin. Label on the following inputs, outputs, flows and storages: precipitation, transpiration, surface run-off, interception, stemflow, infiltration, throughflow, water table, percolation, groundwater storage, groundwater flow, channel storage, evaporation, condensation)

Key Term

Meaning

Transpiration

Interception

Infiltration

Percolation

Throughflow

Surface run-off

Percolation

Evaporation

Condensation

Precipitation

(Label the following features on to your water balance graph:Precipitation (solid line)Evaporation (dotted line)Water surplus (too much water)Water deficit (too little water)Groundwater store rechargeField capacity attained)

(The graph above is a typical water balance graph for the UK. Using the key words from the box above describe how the water balance of the UK changes with the seasons.In the winter monthsIn the summer monthsAt the end of the summer months)

(Exam questionsDescribe how water reaches a river channel in a drainage basin (4 marks)Describe how the water balance of the UK changes with the seasons (4 marks)Explain how vegetation can reduce the amount of water reaching a river channel (4 marks))

(A) (B)

(The two hydrographs above show how the river discharge changes over time. Describe the following features:Peak discharge _____________________________________________________________________Peak rainfall _______________________________________________________________________Lag time __________________________________________________________________________Rising limb ________________________________________________________________________Falling limb ________________________________________________________________________)

(Describe the main differences between the two hydrographs:1)2)3))

(River discharge (the volume of water in a river) is affected by: the amount of precipitation, the amount of evaporation and the amount of abstraction (water removed from river, e.g., for industry).It is also affected by a number of other physical and human characteristics. You will need to know the meanings to each of the following factors and how they affect the lag time. Use the key terms from page 3 to explain your answers.)

(Drainage basin characteristics (size; steep slopes, drainage density (number of streams in the basin)): )

(Amount of water already in drainage basin (antecedent moisture): )

(Rock type (permeable/impermeable): )

(Soil type: )

(Deforestation/Afforestation:)

(Urbanisation: )

(Exam questionsGive the lag time and peak discharge for the river shown to the right (2 marks)How might deforestation of this drainage basin affect its storm hydrograph? Explain your answer. (4 marks))

(Label the diagram above with the four types of fluvial erosion)

Erosion type

Explanation

C or A

H A

C or S

A

(The velocity of a river provides the energy needed for it to transport the eroded material.The eroded material is called its load.Which of the transport types would require the highest velocity?)

Transport type

Explanation

Traction

Saltation

Suspension

Solution

(Quick facts:Competence __________________________________________________________________________________________________________________________________________________________________Capacity ______________________________________________________________________________________________________________________________________________________________________Particle size ____________________________________________________________________________________________________________________________________________________________________)

(Deposition:Deposition happens when a river loses energy. Factors that could cause this are:Reduced rainfall; increased evaporation; increased abstraction; increased friction)

(Quick explanation of the Hjulstrom Curve:Particle size is along the horizontal scale, from clay to boulders.The velocity of the river is along the vertical scale. It is a logarithmic scale.The Hjulstrom curve shows how erosion, transportation and deposition vary with different river velocities)

(Draw a line across at 100 cm/s. At this velocity the river will transport small clay particles (less than 0.01mm) and small pebbles (10-50mm) that have already been eroded. It will erode (and transport) silt (0.01-0.1mm), sand (0.1-1mm) and gravel (1-10mm). It will deposit large pebbles (50-100mm), cobbles and boulders (above 100mm))

(Your turn what are the velocities required to deposit, transport and erode a sand particle (size 0.1mm).Deposition:Transport:Eroson:)

(The critical erosion velocity curve shows the minimum velocity needed to erode material.It takes a higher velocity to erode material than to transport it.The mean settling velocity curve shows the velocity at which particles are deposited. This is the equivalent to the competence of the river.)

(Describe:The pattern of the mean settling velocity curve (this is the boundary between the velocities at which particles are deposited and transported).The pattern of the critical erosion velocity curve (this is the boundary between the velocities at which particles are transported and eroded). Explain why it takes higher velocities to erode silts and clays.)

(Disadvantages of the Hjulstrom curve:1) Velocity where?...2) Shape of load3) Density of load) (Exam questionsOutline the four ways a river can transport its load (4 marks)Outline the four main ways a river can erode material (4 marks)Describe briefly why a river a river drops its load (2 marks)What is meant by the competence of a river?Outline how the critical erosion curve on a Hjulstrom graph varies with particle size (6 marks)Comment on the usefulness of the Hjulstrom curve as a way of determining the main processes in a river channel (6 marks) )

(Label on the diagram where the following features would be found:WaterfallDeltaGorgeMeanderOx-bow lakeDistributaryRapidsV-shaped valleyFlood plainPotholesEstuaryLevee)

(Key facts:The long profile shows the gradient of the river channel from source to mouth. The base level is the lowest point of the river (usually at the sea).Total erosion = Total deposition along the river profile. The rate of erosion/deposition can change.The river will try to smooth out any unevenness in its profile. This is called the graded profile.Upper course: High potential energy as it is so high above sea level.Middle course: High kinetic energy as the river gains velocityLower course: Little potential energy, but lots of kinetic energy.)

(Case study: River Temburong, Brunei (see OS map of lower/middle course at end of this document)Upper course: Ulu Temburong (Belalong), V shape valley, waterfalls and rapidsMiddle Course: Batang Duri to Bangar, meanders, river cliffs/slip-off slopesLower Course: Bangar to Brunei Bay, flat peat swamps, cut-offs & ox-bow lakes)

(Quick facts:Velocity _______________________________________________________________________________Efficiency______________________________________________________________________________________________________________________________________________________________________Wetted perimeter________________________________________________________________________________________________________________________________________________