Rivers Flashcards
Infiltration definition
When water breaks through the soil
Surface flow definition
Water that flows over the surface such as tarmac
Through flow definition
Water that flows through the soil
Percolation definition
Water that sinks deeper into bedrock
Groundwater
water that flows through the bedrock
Transpiration definition
Evaporation from plant leaves
Interception
When precipitation is stopped from reaching the ground by something (e.g. a tree)
Drainage basin definition
A catchment area for precipitation. The rain is drained by one river and it’s tributaries.
Meaning of long river profile
The gradient of the river from source to mouth
What does the Bradshaw model show
Increase as we travel upstream :
-Discharge
-Channel width
-Channel depth
-Average velocity
-Load Quantity
Decrease as we go upstream :
-Load particle size
-Channel bed roughness
-Slope angle
Upper course
-Vertical erosion with hydraulic action, abrasion and attrition
-Traction and saltation at high flow
-Large angular load size
-Steep gradient and narrow river channel
-Boggy saturated land
Middle course
-Channel is deeper and wider
-Vertical erosion decreasing in importance more lateral erosion and deposition
-Suspension main transportation
-Load becomes smaller less angular
-Wider and shallower valleys
-More energy and high volume of water
Lower course
-Channel as it’s widest and deepest and may be tidal
-Deposition>erosion
-Fine material deposited
-Large load but small and round size
-Low energy level, high volume and large discharge
-Lots if industry
Waterfall formation
- Band of hard rock lies over softer and less resistant rock
- As water flows over the cliff it splashed back causing erosion (abrasion and hydraulic action)
- Soft rock eroded more quickly causing under cutting of the hard rock
- The harder rock forms an overhang
- When softer rock can no longer support its weight, it collapses
- Large boulders are deposited at the base of the waterfall
7.The greater power of the water falling to the base moves the material around eroding the base into a deep plunge pool - The cycle begins again and the waterfall begins to retract backwards forming a gorge
Floodplain
-Wide flat area of marshy land on either side of a river, Made of alluvium a sediment deposited by a river when it floods,
-Used for farming as the soils are very fertile
-Wide due to meanders migrating across the floodplain due to lateral erosion. when they reach the edge they erode the valley side.
-When a river floods it deposits silt, creating very flat floodplain. Layer upon layer builds up over many years to form a thick deposit of fertile alluvium
Levee
-Raised river bed found alongside a river in its lower course. It is formed by flooding over many years.
How are Levees formed
-Ridge of sediment deposited naturally to build up the levee.
-During low flow conditions deposition takes place raising the river bed and reducing the capacity of the channel. When flooding occurs water flows the channel sides. Here velocity decreases rapidly leading to deposition of sediment on river banks. First coarser sands are deposited and then the finer silt and mud gradually it can be raised up to 2m.