Rivers Flashcards
Description: Upper Course of a River
Near the source, the river flows over steep gradient from the hill/mountains. This gives the river a lot of energy, so it will erode the riverbed vertically to form narrow valleys.
Description: Middle Course of a River
Here the gradient gets gentler, so the water has less energy and moves more slowly. The river will begin to erode laterally making the itself wider.
Description: Lower Course of a River
Near the rivers mouth, it widens further and becomes flatter. Material transported is deposited.
Formation of a Waterfall + Gorge
1) Rivers flow over alternating rock types
2) Rivers erode softer types faster creating a step
3) Further hydraulic action and abrasion form a plunge pool beneath
4) Hard rock above is undercut leaving ‘cap rock’ which collapses providing more material for erosion.
5) Waterfall retreats leaving steep sided gorge.
Formation of Levees + Floodplains
When a river valley floods, silt is depositied on the valley floor. Closer to the rivers banks, the heavier materials build up to form natural levees.
- Nutrient soil = good for farming
- Flat land = ideal for building houses
Formation of Interlocking Spurs
The river swings around the ‘fingers’ of land to find the easiest route.
Formation of Ox-Bow Lakes
1) Erosion of outer bank forms river cliff. Deposition inner bank forms slip off slope
2) Further hydraulic acton and abrasion of outer banks, nck gets smaller.
3) Erosion breaks through neck, so river takes the fastest route, redirecting flow.
4) Deposition cuts off main channel leaving an oxbow lake.
Physical Causes of Flooding
- Prolonged + Heavy Rainfall
- Relief
- Geology
Human Causes of Flooding
Land Use:
- Impermeable substances used like concrete and tarmac = surface runoff
- Deforestation reduces interception and increases runoff
Environmental Consequences of Flooding
- Landslides
- Soil Erosion
- Loss of Habitats
Human Consequences of Flooding
- Loss of Property + Belongings
- Disruption to Business + Transport
- Death/Injury
Definition: Precipitation
Moisture falling from clouds as rain, snow or hail
Definition: Interception
Vegetation preventing precipitation from reaching the ground
Definition: Surface Runoff
Water flowing over surfaces of the land into rivers
Definition: Infiltration
Water absorbed into the soil from the ground