Rivers Revision

SDME preparationJan 2012A Damming report- why are some strategies for flood management more sustainable than others?Rivers RevisionThe outline- 14 lessons till examsRevision- causes- hydrological cycle, drainage basin system, storm hydrographs, influences on the shape of hydrographs and examples of flooding in MEDCs and LEDCsUse the resource booklet to plan for the exam

Plan and write decision making answers

Hydrological cycle and drainage basin system

Sort the boxes into inputs / stores / flows / outputsThe drainage basin systemRiverprecipitationInterceptionstemflowinfiltrationSoil moisture storagepercolationGroundwater storageSurface run offthroughflowGroundwater flowtranspirationUse P Use the drainage basin system diagramHow can humans influence the diagram / what areas cant humans influence

What is a flood hydrograph?

Rising limbFalling limbPeak dischargePeak rainfallWrite a definition of lagtime.Calculate the lagtime shown on this hydrograph.storm flownormal (base) flowHydrographsI = Lagtime

What are Hydrographs?Hydrographs are graphs which show river discharge (the amount of water in a river) over a given period of time and show the response of a drainage basin and its river to a period of rainfall.

Discharge is measured in cumecs (cubic metres per second). This can be calculated by multiplying river velocity by channel volume at a given point and time.

Success criteriaUsing the graph paper and informationCreate bars of the rainfallCreate a line of the flowEither stick on the labels of the features of a hydrograph or write them out and add labelsThen using the scenarios- work out where each scenario goes on the graph- give reasons for your answer

Variations in the shape of a Hydrograph:The shape of a hydrograph is determined by the speed in which flood waters are able to reach the river. The nature of the drainage basin therefore has a great influence on the way a river responds to a river as it will determine the types and speeds of the flow of water to the river.Sketch diagram time...Can you draw a label sketch diagram of: A general flood hydrograph.A flood hydrograph for a drainage basin that experiences a storm just after a new housing estate has been built. A flood hydrograph for a drainage basin that has lots of vegetation.

What is a drainage basin?How does the drainage basin system operate?What is a flood hydrograph?What factors influence the shape of a flood hydrograph?

Learning objectives

Success criteriaDraw different shaped storm hydrographsSort factors into the two shaped graphs to show how it influences the shape of the responseRead storm hydrographs correctly from an example and explain using knowledge of the drainage basin system and drainage basin characteristics why storm hydrographs have certain shapes and response times.

HydrographsWhat affects the shape of a hydrograph?Land useType and amount of precipitationGeology and soilGradient of the valley sidesDrainage density

How do trees reduce flooding?trees intercept the rainevapotranspiration reduces the amount of water that reaches the riverwater is taken through the roots and so less enters the river What factors influence the shape of a hydrograph?The hydrographs a and b have been produced from the same storm event but from different drainage basins.

What could cause 2 peaks in a hydrograph?HydrographsCompare these two hydrographs.

Which one has the largest lag time? Explain your answer.

Hydrographs