River Landscapes Flashcards
What is a drainage basin?
The area of land drained by a river
What parts of a river are included in a drainage basin?
Watershed, source, mouth, tributaries and confluences
How does precipitation travel to a river?
Travels across the surface of the drainage basin and underground through soil or rocks
What does a long profile show?
The height and distance downstream from a river’s source to its mouth
What does a cross profile show?
The depth and width of the channel at any point along the long profile.
What are the 3 sections of a river?
Upper, middle, lower
What is abrasion in rivers?
Sediment carried by river rubbing along the river channel
What is attrition in rivers?
Sediment carried by the river colliding with one another to become smaller and more rounded
What is hydraulic action in rivers?
The sheer force of the water eroding the channel and valley
What is lag time?
The difference between peak rainfall and peak discharge
What is the rising limb?
The rapid rise in water after a period of heavy rainfall
What is saltation in rivers?
Sediment being transported by bouncing along the riverbed
What is solution in rivers?
The process of rock minerals being dissolved in water
What is suspension in rivers?
The process of sediment being transported by the river water
What is traction in rivers?
The process of sediment being rolled along the riverbed
What is weathering in rivers?
The sub-aerial breakdown and decay of rocks in the river valley - chemical, biological, mechanical
What type of material is first deposited when a river loses energy?
The heaviest
How are interlocking spurs formed?
- A river erodes softer, less-resistant rock in the valley
- Harder, resistant rock is left
Where in the course of a river are interlocking spurs found?
Upper course
How are waterfalls and gorges formed?
- A layer of hard, more resistant rock lays over a band of soft, less resistant rock
- Hydraulic action and abrasion erode the less resistant rock
- This creates a waterfall, plunge pool and eventually a gorge as it retreats
Where in the river course are waterfalls and gorges found?
The upper course
What are meanders?
Bends in the river
How are meanders formed?
Erosion and deposition:
1. HA + abrasion laterally erode the outer bend of a river channel
2. Sediment is deposited on the inner bend of the river
How are oxbow lakes formed?
- A river erodes the meander neck and flows through a new, straight channel
- Deposition occurs at the neck and seals off the meander bend
- Creating an oxbow lake
What is alluvium?
Fine sediment deposited by rivers
How are floodplains formed?
Erosion + deposition:
During floods, river deposits alluvium on the floodplain
How are oxbow scars created?
By oxbow lakes drying up
What part of the river course are floodplains found in?
Middle and lower
What part of the river course are meanders and oxbow lakes found in?
Middle and lower
What are levees?
Natural embankments of deposited sediment along the banks of a river. They are usually deposited during flooding.
What part of the river course are levees found in?
Middle and lower
What are mud flats?
Areas of sediment formed by deposition as the river meets the estuary
What part of the river course are mud flats found in?
Lower
What is an example of a river impacted by human activity/processes?
River Tees
How is the the River Tees used by humans?
Cow Green reservoir is used for water supply, the river valley is used for sheep farming, Seal Sands is a place of specific scientific interest, Tees Barrage used for water sports, etc.
When and why does a river flood?
When the discharge exceeds the channel’s volume, so water overflows to nearby land
Name 3 factors that can lead to flooding.
Intense rainfall, duration of rainfall, snow melting, geology, relief, etc.
What does a storm hydrograph show?
How the river responds to a flood event, displaying the rainfall and discharge of a given flood event
How does the Environment Agency manage flooding?
Hard and soft engineering
Name 3 hard engineering techniques in the river.
Embankments, channelisation, dams and reservoirs
Name 3 examples of soft engineering in the river.
Wash lands, river restoration, flood-plain zoning
What happened on 16th August 2004?
Boscastle experienced a flood.
Name 2 factors that led to the flood at Boscastle.
89mm of rain fell in one hour, ground in the drainage basin was satured from previous precipitation, the steep and narrow river channel limited infiltration and increased surface runoff…
Name 3 impacts of the flood at Boscastle.
100 homes and business destroyed, tourist industry affected, £4.5 million spent on a flood defence scheme implementing hard engineering tactics
What happened in July 2007?
Tewkesbury, Gloucestershire experienced a flood
Why did the flood at Tewkesbury happen?
Prolonged, intense rainfall, satured grounds caused the rivers Severn and Avon to burst their banks
Name 2 impacts of the flood event at Tewkesbury.
2 people died, 48,000 homes were affected, business closed, cost £50 million…
Name a response to the flood at Tewkesbury.
Since 2007, flood defences and flood warning schemes have been set up to prevent future flooding in the area
