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Factors that affect flood risk…

Factors that affect flood risk…. Natural & Human. The hydrograph – a reminder!. Key Fact: Shorter Lag Time + Steeper Rising Limb = Increased Flood Risk. Tasks:. With partner list all of the things that may increase flood risk in a drainage basin / river system…

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Factors that affect flood risk…

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  1. Factors that affect flood risk… Natural & Human

  2. The hydrograph – a reminder! Key Fact: Shorter Lag Time + Steeper Rising Limb = Increased Flood Risk

  3. Tasks: • With partner list all of the things that may increase flood risk in a drainage basin / river system… • Make one list of natural factors that may increase flood risk or cause flooding and another for human factors that may increase flood risk or cause flooding • Now try to decide what are the most important three factors in each list! – explain why each factor increases flood risk (think about hydrographs and lag time) • Share your answers with the class.

  4. Natural Factors 1 • Weather & Climate • Precipitation type (Rain Vs Snow) • Length of storm in time (leading to saturation) • Intensity of rainfall (precipitation exceeds infiltration rate) • Seasonality • Temperature

  5. Natural Factors 2 • Surface Type & Geology • Permeability of surface • Soil type • Rock Type

  6. Natural Factors 3 • Vegetation • Type (trees, bushes, grasses) • Seasonal effects on vegetation (summer vs. winter) • Coverage (bare ground Vs Vegetation cover) • Interception & storage

  7. Natural Factors 4 • Relief (shape of the land) • Shape of drainage basin • Size of drainage basin • Drainage density

  8. Human Factors 1 • Urbanization • Surface permeability • Drainage systems • Vegetation removal

  9. Human Factors 2 • Agriculture • Changes to vegetation • Animals • Erosion and runoff

  10. Human Factors 3 • Changes to the drainage basin • River management (dams, flood relief channels) • Flood prevention schemes (levees, dredging) • Straightening • Deforestation

  11. Tasks 2: • Now use your text book (New Wider World) • Read pages 280 – 281 to reinforce your understanding of these flood risk ideas • Now read the case study of flooding in Bangladesh p.288-289… make a mind map to represent this flood event – include all of the factors hat led to this flooding… use one color for the natural factors and another color for the human factors.

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