HKDSE Geography/M2a/Hydrographs and Flooding

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Flooding is the condition in which the water in a river overflows.

Hydrograph[edit]

TODO: Need actual hydrographs

  • Peak discharge is the maximum river discharge during a certain period of time.
  • A hydrograph's rising limb shows the time during which discharge increases.
  • A hydrograph's falling limb shows when discharge decreases.

Factors[edit]

All the factors above that affect discharge affect flooding. The greater the discharge, the greater the flood risk. In addition:

  • Elongated drainage basin → Time lag ↑ → Floods ↓
  • Circular drainage basin → Time lag ↓ → Floods ↑
  • Straight river → Time needed for river to flow away ↑ → Floods ↓
  • Meandering river → Time needed for river to flow away ↑ → Floods ↓
  • Lakes ↑ → Act as a buffer during floods → Capacity ↑ → Bankfull discharge ↑ → Floods ↓