HKDSE Geography/M2a/Hydrographs and Flooding
< HKDSE Geography | M2a
Flooding is the condition in which the water in a river overflows.
Hydrograph
[edit | edit source]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 | edit source]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 ↓
| Drainage Basins |  | |
|---|---|---|
| Fluvial Landforms | Erosional Landforms (upper course) · Meandering (middle and lower courses)† · Depositional Landforms (lower course) | |
| Humans and Rivers | ||
*Refers to 'attributes' like drainage pattern, stream order and so on. † Meandering involves both erosion and deposition. | ||