Hydrology & Fluvial Geomorphology
Rivers, flooding, and water management
A drainage basin is land drained by a river and tributaries. Inputs: precipitation. Stores: lakes, groundwater, soil moisture. Transfers: infiltration, throughflow, surface run-off, groundwater flow. Outputs: evapotranspiration, river discharge.
Erosion types: **Abrasion** (rocks scraping bed), **Hydraulic action** (water force), **Attrition** (rocks colliding), **Solution** (dissolving rock).
Transportation: **Traction** (rolling boulders), **Saltation** (bouncing stones), **Suspension** (fine particles), **Solution** (dissolved material).
Deposition happens when rivers slow down and lose energy.
Landforms: **Meanders** — erosion on outer bend, deposition on inner. **Oxbow lakes** — cut-off meanders. **Deltas** — deposition where river meets sea (e.g., Indus Delta near Thatta).
Flood Management: Hard engineering: dams, embankments, channelisation. Soft engineering: floodplain zoning, afforestation, managed retreat.
Key Points to Remember
- 1Drainage basin hydrological cycle
- 2River processes: erosion, transportation, deposition
- 3Flood management strategies
- 4River landforms
Pakistan Example
The Indus River — Pakistan's Lifeline and Hydrology Textbook
The Indus flows 3,180 km from Tibet, depositing sediment across Punjab's fertile plains. Near Thatta, it forms a massive delta. The 2022 floods submerged one-third of Pakistan — deforestation in northern watersheds increased surface run-off, overwhelming defences like Tarbela Dam.
Quick Revision Infographic
Geography — Quick Revision
Hydrology & Fluvial Geomorphology
Key Concepts
The Indus River — Pakistan's Lifeline and Hydrology Textbook
The Indus flows 3,180 km from Tibet, depositing sediment across Punjab's fertile plains. Near Thatta, it forms a massive delta. The 2022 floods submerged one-third of Pakistan — deforestation in northern watersheds increased surface run-off, overwhelming defences like Tarbela Dam.