Drainage Basins and Why Rivers Flood · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Why some rivers flood in a flash

Geography · Physical Geography · ages 14-16
Name ______________________   Date ____________

  1. Which route brings storm water to the river fastest?

    • Deep groundwater flow
    • Slow creep through soil
    • Overland surface runoff

  2. Rain falls inside a basin divide. Where does it end up?

    • In that basin's own river
    • In a river two valleys over
    • Nowhere, it vanishes

  3. A drainage basin is all the land that drains into one river.

    Circle one:   True   False

  4. After days of gentle drizzle the river rises slowly. Why?

    • Fast overland flow rules the basin
    • Slower soil and groundwater routes rule
    • The divide moved uphill

  5. A hydrograph shows peak flow just after peak rain, tall and narrow. What kind of river is this?

    • A slow steady river
    • A flashy river with little warning
    • A drying river with no flood risk

  6. Sealing soil with concrete slows water down and cuts flood risk.

    Circle one:   True   False

  7. Two basins get the same storm. Basin A peaks in an hour, B in a day. What differs?

    • The amount of rain that fell
    • How fast each basin delivers water
    • The names of their rivers

  8. A new estate paves a hillside above a town. Why might the town flood?

    • Paving shunts storm water fast to drains and the channel
    • Paving drinks up extra rain like a sponge
    • Paving moves the divide to the town
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Why some rivers flood in a flash W1-mt_Vu4fTs7goJ-s1

  1. Overland surface runoff · Surface runoff skips soaking in, so it reaches the channel first.
  2. In that basin's own river · Inside the divide means inside the system. All of it feeds the same channel.
  3. True · One river, one fence of high ground: that is the whole definition.
  4. Slower soil and groundwater routes rule · Drizzle soaks in, so slow routes rule and the rise stays gentle.
  5. A flashy river with little warning · Short lag plus tall narrow peak is the signature of a flashy river.
  6. False · Sealed soil blocks soaking in and shunts water to drains, raising flood risk.
  7. How fast each basin delivers water · Same storm, different lags: the basins handle rain differently.
  8. Paving shunts storm water fast to drains and the channel · Sealed slopes skip soaking and deliver storms downstream in a rush.
Worksheet · LightMySky