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The Water Cycle and Water Insecurity

Human causes of flooding

  • 3 things to know
  • Papers 1 and 3

Overview

How deforestation, urbanisation, agricultural drainage and land use changes shorten lag time and raise peak discharge, and how channelisation, embankments, dams and upstream flood protection can increase flood risk.

What you need to know

Answer each one before you reveal it.

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Evaluation

What effect do land use changes have on lag time and peak discharge?

Evaluation

What risk do dams pose during extreme flood events?

Key term

Why does urbanisation increase flood risk in a catchment?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    How does deforestation affect interception and flood risk?

    Model answer

    Removing trees reduces interception of rainfall by vegetation, allowing more water to reach the ground surface quickly.

  2. 2

    Why does urbanisation increase flood risk in a catchment?

    Model answer

    Urbanisation creates impermeable surfaces such as concrete and tarmac that prevent infiltration and increase surface runoff.

  3. 3

    How does agricultural drainage affect water transfer in catchments?

    Model answer

    Drainage ditches and field drains speed the transfer of water from fields to rivers, increasing flood peaks.

  4. 4

    What effect do land use changes have on lag time and peak discharge?

    Model answer

    Land use changes reduce lag time and increase peak discharge by speeding up water transfer to river channels.

  5. 5

    How does channelisation affect flood risk?

    Model answer

    Channelisation increases flow velocity, moving floodwater downstream faster and potentially increasing flood peaks elsewhere.

  6. 6

    Why can embankments worsen flooding in some areas?

    Model answer

    Embankments prevent water from spreading onto floodplains, removing natural storage and transferring flood risk downstream.

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