HKDSE Geography/M2a/Hydrographs and Flooding

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

Hydrograph
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
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 ↓