Processes that shape fluvial environments
River Hydrology and Fluvial Processes
- Important part of Hydrological Cycle is the drainage basin system: catchment area of a river from where it gets its water supply.
- It includes inputs (precipitation), outputs (evaporation, transpiration), flows (surface run-off, throughflow), and storage (in soil, vegetation, lakes).
- Throughflow and percolation are the movements of water within the soil and underlying rock layers.
- The speed and amount of throughflow and percolation depend on the soil and rock type.
Channel Formation and Development
- River channels form through erosion, which wears away the bed and banks of the river.
- Transportation is the process of eroded materials being carried along by the river.
- Deposition occurs when the velocity of the river decreases and it no longer has enough energy to carry its load.
River Erosional Processes
- Hydraulic action: the force of water hitting the river banks.
- Abrasion/corrasion: Pebbles in the water scrape and wear away the river bed and banks.
- Attrition: Material transported by the river collides and rubs together, becoming smaller and rounder.
- Solution/corrosion: Certain types of rock are dissolved by the river's water.
River Transportation Processes
- Traction: Larger stones and boulders rolled along the river bed.
- Saltation: Small pebbles and stones are bounced along the river bed.
- Suspension: Fine light material is carried along within the water.
- Solution: dissolved minerals are carried within the water.
River Landforms
- Interlocking spurs: In the upper course the river erodes the sides of the valley which creates distinctive 'zig-zag' landscape.
- Waterfall: Formed when there is a layer of soft rock followed by hard rock, the soft rock erodes faster which creates a plunge pool at the base of the hard rock.
- Meanders and Ox-bow lakes: Formed in the middle and lower course of the river where it has more energy and volume.
- Floodplain and levees: Levees are formed when a river floods and the heaviest material is deposited closest to the river channel.
River Management and Flood Contingency
- Hard engineering techniques like dams, levees, and floodwalls aim to physically prevent a river from flooding.
- Soft engineering techniques involve working with nature to manage the flood risk. These are often more sustainable as they aim to increase the capacity of the river channel and the surrounding floodplain.
Case Studies
- Understanding and explaining case studies of particular river systems, such as the River Severn in the UK or the Mississippi River in the USA, can deepen your understanding of how these processes occur in real-world scenarios.