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River Flooding[1]
River Flooding[1]
River Flooding[1]
River Flooding[1]
River Flooding[1]
River Flooding[1]
River Flooding[1]
River Flooding[1]
River Flooding[1]
River Flooding[1]
River Flooding[1]
River Flooding[1]
River Flooding[1]
River Flooding[1]
River Flooding[1]
River Flooding[1]
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River Flooding[1]

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  • 1. River flooding Why do rivers flood?
  • 2. Copy the table + sort the following hydrological cycle processes into the right sections Surface Runoff Precipitation Condensation Infiltration Throughflow Transpiration Soil Moisture Lake Stream Flow Interception Groundwater Groundwater flow Outputs Flows Stores Inputs
  • 3. Flooding <ul><li>On your table, circle the most important processes that may cause flooding </li></ul>
  • 4. Homework <ul><li>Investigate a major flood event in the UK </li></ul><ul><li>Include: </li></ul><ul><li>Location </li></ul><ul><li>Causes </li></ul><ul><li>Effects (e.g. deaths, costs, damages) </li></ul><ul><li>E.g. floods in Wales 2009 </li></ul>
  • 5. The Flood / Storm Hydrograph <ul><li>Hydrographs are used to show the relationship between precipitation and discharge (the amount of water passing in the river channel) . </li></ul><ul><li>Hydrographs are used to predict whether a river is likely to flood . </li></ul><ul><li>Discharge is measured in Cumecs (cubic metres of water per second). </li></ul><ul><li>Lag Time is the delay between peak precipitation and peak river discharge. </li></ul><ul><li>Short Lag Times means water enters the river system very quickly following rainfall </li></ul><ul><li>Long Lag Times means water takes a longer time to enter the river system following rainfall </li></ul>
  • 6. Lag times <ul><li>So a lag time changes depending on the characteristics of the river basin </li></ul><ul><li>What kinds of things might cause rainfall to enter the river more slowly or more quickly? (Tip – think about factors that slow down infiltration or increase surface run-off) </li></ul><ul><li>Short lag times = are caused by steep slopes , impermeable rock, sparse vegetation and a small drainage basin. These mean surface run-off is high so water enters the river quickly following precipitation. </li></ul><ul><li>Long lag times = are caused by gentle slopes, permeable rock, dense vegetation and a large drainage basin. These mean surface run-off is lower, there is more interception and infiltration so water takes longer to get to the river channel. </li></ul>
  • 7. Questions <ul><li>Question 5 (a,b,c) Page 75 </li></ul><ul><li>P76/77. Which hydrograph do you think is for a rural location? Which is urban? Why? </li></ul>
  • 8. Question 5 (a,b,c) Page 75 <ul><li>The discharge of the river in cumecs in response to precipitation </li></ul><ul><li>8 m 3 /sec </li></ul><ul><li>12 hours </li></ul>
  • 9. What are the causes of flooding? <ul><li>Make a copy of the diagram on page 76 </li></ul><ul><li>Colour classify each cause into either physical or human . </li></ul><ul><li>Complete activities 2-4 </li></ul><ul><ul><li>2. 2 marks </li></ul></ul><ul><ul><li>3. 3 marks </li></ul></ul><ul><ul><li>4. 2 marks </li></ul></ul>
  • 10. Answers <ul><li>2. The UK’s population is still rising, for example from migration, and new housing is needed. There is little space in the UK and land is cheap on floodplains. </li></ul><ul><li>3. Using permeable surfaces in urban areas, ploughing across hills instead of up and down, planting trees </li></ul><ul><li>4. The lag time is shorter and the peak discharge higher in urban areas when compared to rural areas. </li></ul>
  • 11. Causes of Flooding <ul><li>Precipitation - Heavy rainfall over a long period = creates saturated soil and surface run-off </li></ul><ul><li>Flash Floods - Hot dry areas where the land is baked hard causes flooding if there is an intense burst of heavy rainfall - water cannot infiltrate and results in rapid run-off. </li></ul><ul><li>Snowmelt - When temperatures rise and snow melts the stored precipitation is released as run off as infiltration will be low as the ground is still frozen. </li></ul><ul><li>Deforestation - When trees are cut down this reduces interception, transpiration and storage by the trees. This results in increased surface run-off </li></ul><ul><li>Urbanisation - When land is urbanised vegetation is removed and the land is covered in concrete and tarmac. These surfaces are impermeable and increase surface run-off. </li></ul>
  • 12. What are the impacts of river flooding?
  • 13. What are the impacts of river flooding?
  • 14. Landforms revision <ul><li>Right, now for something creative </li></ul>
  • 15. Ready, Steady, Dough… <ul><li>Work in pairs/groups to make a play-dough model showing how meanders and ox-bow lakes form </li></ul><ul><li>You could make paper labels to add to it </li></ul><ul><li>Now present your model to another group </li></ul><ul><li>You should explain your model and the processes involved </li></ul><ul><li>The listening group should tell you one thing they like and suggest one thing to improve </li></ul>
  • 16. Poster task <ul><li>In pairs or groups, create a poster to show what you have learnt about rivers. </li></ul><ul><li>Include: </li></ul><ul><li>- Types of erosion </li></ul><ul><li>- Upper / middle / lower course features </li></ul><ul><li>- Landforms </li></ul>

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