The Water Cycle - Rivers Flashcards
What is a drainage basin?
The area of land that is drained by a river and its tributaries - sometimes referred to as the catchment
What causes turbulent flow?
Obstacles in the channel or the river bed can disturb the thalweg
What does energy in a river depend on?
Height the water has to descend, mass of water available
What is flocculation?
Flocculation occurs when fresh water meets salt water which causes chemical setting of the clays and silts to occur. The cogulation of the particles causes them to sink more rapidly and creates extensive areas of mudflats
What does the Hjulstrom curve show?
The relationship between the size of sediment and the velocity required to erode, transport and deposit it
State one advantage and one disadvantage of afforestation
Advantage - new ecological habitats and acts as carbon sink
Disadvantage - may impact existing food webs and ecosystems
State one advantage and one disadvantage of channel straightening
Advantage - velocity increases and there is a reduced chance of flooding at the straightened section
Disadvantage - may increase risk of flooding further downstream
State one advantage and one disadvantage of dams
Advantage - can generate hydroelectric power
Disadvantage - impact ecosystems
State one advantage and one disadvantage of doing nothing
Advantage - over longer periods biodiversity can increase as new habitats are created
Disadvantage - unmanaged rivers can damage infrastructure on river banks
State one advantage and one disadvantage of dredging
Advantage - deepens river allowing larger vessels through
Disadvantage - may disrupt aquatic ecosystems, lots of carbon and sewage is lifted out
State one advantage and one disadvantage of floodplain zoning
Advantage - reduces flood damage by minimising impact on more important property
Disadvantage - can only be done in new developments and can reduce value of land
What are some examples of hard engineering?
Dams and reservoirs, channel straightening, flood gates and levees
What are some examples of soft engineering?
Do nothing, afforestation, floodplain zoning, dredging
What is the capacity of a river?
The amount of material a river can carry - total volume of the load. Increases to the 3rd power of its velocity
What is the competence of a river?
The maximum size of load that a river can carry. Increases to the 6th power of its velocity
Describe the river catchment of the River Tweed
Horseshoe shaped basin, mainly sedimentary rock (large groundwater stores), upper course has many trees so high interception rates, many tributaries damned by beavers
Describe the flood events of the River Tweed
2015 - Peebles was flooded and several houses and a nursing home had to be evacuated
2014 - Flood embankment breached and roads in Merlindale blocked
Describe the river management of the River Tweed
River restoration of Eddleston Water (near Peebles) - a tributary of the River Tweed - including remeandering and afforestation
Describe the land uses of the River Tweed
80% of land is used for agriculture, the river also passes through many coniferous woodlands
