Title

The issue: A Damming report why are some strategies for flood management more sustainable than others?Look through the resource bookletWhat information do you need to know?

Write it down in your books

Share your ideas with another pairThe basics!What is a river?What is a drainage basin?

What is a flood?What causes a flood?

What is a hydrograph?

What is resource 1 about?

What possible questions could we be asked?Task 1What is a drainage basin?Why is this relevant to the exam?

You need to know the following terms.

CatchmentThe area from which water drains into a particular drainage basin.Tributary A river which joins a larger river.ConfluenceThe point at which two rivers join.Watershed The boundary dividing one drainage basin from another- a ridge of high land.What is a drainage basin?SourceThe upland area where the river begins.MouthWhere the river flows into the sea, or sometimes a lake.Do you know your drainage basin terminology?

You also need to know what a drainage basin looks like on a map

WatershedTributaryMatch the label to the correct letterConfluenceabcSourcedSketch the river showing its catchmentAdd the following labels Watershed, Confluence, Tributary

Examination question

XYStudy the map of a river valley below:Sketch a cross-section of the river valley from X to Y.Label two features of this river valley.State at what stage of a rivers course you would expect to find this type of valley. Give reasons for your answer.Height (m)XYWhat is a river?

How does water enter a river?

Why would a river flood?The water cycle more detailed

12The water cycle definitions!

You need to understand water enter a river in order to understandhow it floodsThe drainage basin

riverevapotranspirationprecipitationthroughflowsurface runoffgroundwater flowwater tableinterceptionpercolationinfiltrationDrainage basin systemWhat is a hydrograph?What information does it provide?

What do the key terms mean?What is a flood hydrograph?

Rising limbFalling limbPeak dischargePeak rainfallWrite a definition of the key words.Calculate the lagtime shown on this hydrograph.storm flownormal (base) flowHydrographsI = LagtimeWhat would a hydrograph look like if it was about to flood?What is a flood?

Why do rivers flood?

Complete the work sheet about what causes flooding

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.

Imagine that these two areas have had the same amount of rain over a 24-hour period. Draw a possible hydrograph for each of these areas.ABHydrographs

What could cause 2 peaks in a hydrograph?HydrographsResource 1What else do you need to know?

What type of questions could you be asked about this resource (use last years paper to help you)What is the lag time in each drainage basin?

Which river is more likely to flood and why?

Compare the 2 drainage basins and explain why are different.

Drainage basin 1:What does the word discharge mean? (1)What does the word lag time mean? (1)It is the volume of water in cubic metres in the river every second.

It is the time between the maximum rainfall and maximum discharge.Describe the shape of the storm hydrograph in resource 1 (4).

Mark for shape and figures. 2 for rain/ 2 for discharge.The rainfall begins at 0mm at first, then increases to its maximum of 30mm after 1 hour, it then decreases back down to 0mm after 2 hours. The discharge begins at its minimum of 1m3/sec, then rises rapidly to a maximum of 14m3/sec after 3 hours, then decreases rapidly down after 5 hours, then remains fairly steady.Describe the river valley shown in photo A. (2)The river valley shows steep hills, and a grassy landscape with no trees. It is a rural area, and the river looks quite narrow. Give the four and six figure grid reference that the photo is taken from. (2)How high is the tallest point shown on the map? (1)What direction did the photographer face to take the photo? (1)

8086 and 802867

600m

East

Drainage basin BDescribe the shape of the storm hydrograph in resource drainage basin 2 (4).

The rainfall begins at 0mm at first, then increases to its maximum of 30mm after 1 hour, it then decreases back down to 0mm after 40mins. The discharge begins at its minimum of 1m3/sec, then rises gradually to a maximum of 4m3/sec after 5 hours, then decreases gradually down to 1.8m3/sec at 9 hours.

Describe the river valley shown in photo A. (2)

The river is fairly narrow and shallow, and there are lots of trees. There are some deciduous and coniferous trees.Give the four and six figure grid reference that the photo is taken from. (2)How high is the tallest point shown on the map? (1)What direction did the photographer face to take the photo? (1)

8585 858858

481m

East

Compare the hydrographs in drainage basin A and B.(2)

(Give two differences)In drainage basin A the maximum discharge is very high at 14m3/sec, whereas in B it is lower at 4m3/sec.In drainage basin A the rising and falling limb are very steep, whereas in B they are a much gentler curve.In both drainage basins the rain falls for about 1hur and 30mins.The lag time in photo A is 2 hours, whereas in Drainage basin B it is nearly 4 hours long.Compare the lag time in both drainage basins (1)The lag time in photo A is only 2 hours, whereas the lag time in photo B is nearly 4 hours long. (1)Explain why the lag time differs between drainage basin A and B. (4)The lag time is shorter in A, this is because the land is steeper, so more water will travel by surface run off, which is quicker, so all the water will reach the river at the same time, whereas in photo B the land is flatter, so water will travel slower to the river. (2)

There are less trees in A, so less water will be taken in by the roots and transpired back to the atmosphere, whereas in B there are lots of trees, so lots of water will be taken in by the roots and transpired. (2)

In addition, the roots of the grass in photo A will be short, and will not hold the soil together, so it will be eroded, and will wash into the river, and fill it up with silt, so less water can be contained, whereas in photo B the tree roots will hold the soil together, so it doesnt get washed into the river. (2)