river landscapes Flashcards
what is a drainage basin
Area of land drained by a river and its tributaries
What do you call the edge of the river basin?
Watershed
Confluence versus tributary
tributary: small stream which joins
Confluence: where it joins
Vertical versus lateral erosion
vertical is downward
Lateral is the sides
Three features found in the upper course
interlocking spurs
Water fall
Gorges
how do interlocking spurs form?
Stream in V-shaped Valley (vertical erosion) winds around areas of hard rock
how do waterfalls form?
When river flows over hard rock followed by soft rock, soft rock roads quicker (abrasion and hydraulic action)
Step is formed
Force of water under hard rock (hy ac) creating plunge pool
hard rock overhang and eventually collapses
hy ac and attrition a road these fallen rocks which then become transported away by the river
how do gorges form
waterfall process repeats and waterfall move upstream, creating an almost vertical valley
which landforms are in the middle course?
Meanders and Oxbow Lakes
features of meanders
Rivercliff
Slip off slope
Thalweg
Undercutting
Lateral erosion
how do Oxbow lakes form?
lateral erosion narrows neck of meander
They connect, meaning water flows mostly in a straight line, and slowly around the redundant loop
This causes lots of deposition in the redundant loop and on the step of slopes until oxbow Lake is cut off
Lake evaporates and leaves meander scar
What landforms are in lower course?
Flood planes and levees and estuaries
What is a floodplain?
large area of Flatland either side of a river that is prone to flooding
Features of flood plains
layers of allurium (& in meander scars)
Levees
Meander migration
River Bluff
meander scar
Oxbow Lake
Reeds and marsh plants
How did levees form?
when flow is slow, deposition occurs on the river bed, making it prone to flooding. When this does flood, heavier and corser sediment is deposited as it is more difficult to transport.
finer sediment is carried further on the floodplain
riverbed continues to build bed load, meaning the banks become higher and wider (levees)
Features of estuaries
High tidal range
At high tide, rivers cannot flow, velocity Falls, sediment deposits, mudflats, salt
marshes
very wide
tidal bores (waves upstream)
What do you call it when water soaks into the soil and flows into the river from the soil?
infiltration
Throughflow
what do you call it when soil moisture soaks into the rock below?
Percolation
Where does water go after percolation?
Groundwater and then groundwater flow
how does precipitation evaporate without touching the ground?
Interception from plants, evapotranspiration
three physical factors that can increase flood risk
• prolonged precipitation, over saturated soil
• geology/rock type – impermeable rocks promote surface run-off to river
• Relief – steep mountainous environments encourage rapid transfer towards rivers
Two human factors that increase flood risk
• urbanisation – creates impermeable surfaces
• deforestation – prevents interception
what do you call the time between peak rainfall and peak discharge on a hydrograph?
Lag time
what do you call the increase/decrease on a hydro graph
Rising/falling limb
For examples of hard engineering to control flooding
dams and reservoirs
Channel straightening
raising Embankments
Flood relief channels
Three examples of soft engineering to control flooding
floodplain zoning (restricting land uses to certain zones on floodplain)
Afforestation
River restoration
why does Banbury need flood management schemes?
History of flooding including £12.5 million damage in 1998
Features of Banbury flood storage
2.9 km embankment - reservoir now where material was taken
This created a flood storage area
One social one economic and one environmental benefit of Bandberry scheme
• raised motorway stays open during flood
• over 400 houses and 70 businesses protected
• Material from embankments was extracted locally - small reservoir
