1.1C - Rivers Flashcards
(3)
How does a river’s long profile vary over its course?
- Upper course: Steepest
- Middle course: Less steep
- Lower course: Shallowest.
(3)
How does a river’s cross profile vary over its course?
- Upper course: v-shape valley, narrow channels
- Middle course: u-shape valley, wider channels, deeper
- Lower course: low lying land, deepest.
(3)
What landforms are created by erosion in the upper course?
- Waterfalls
- Gorges
- Interlocking spurs
(5)
How does a waterfall form?
- Soft rock erodes by HYDRAULIC ACTION and ABRASION.
- creates a STEP.
- water flows over the STEP = MORE EROSION
- Hard rock UNDERCUT by EROSION
- They collapse and create a DEEP PLUNGE POOL.
(3)
How does a gorge form?
- MORE UNDERCUTTING = more collapsing
- WATERFALL RETREATS.
- Gorge formed.
(3)
How do interlocking spurs form?
- river has LOW ENERGY
- to LATERALLY ERODE
- they CURVE AROUND HILLS
(4)
In the middle course, how do meanders form?
- Water travels via THALWEG
- OUTER BEND OF RIVER = EROSION -> river cliffs
- INNER BEND = DEPOSITION -> slip-off slopes.
- Forms horseshoe shape –> MEANDER
(6)
In the middle course, how do ox-bow lakes form?
- More EROSION in outer bend
- Forms a NECK.
- River breaks through the NECK
- River travels the shortest route.
- DEPOSITION CUTS the NECK
- OX-BOW LAKE.
(3)
In the lower course, how does a levee form?
- Heaviest material gets DEPOSITED onto river channel
- as it loses its ENERGY
- BUILDING UP on river channels = LEVEE.
(1)
What is lag time?
The delay between peak discharge and peak rainfall.
(4)
How does the amount of rainfall affect the risk of flooding?
- MORE RAINFALL
- INCREASE IN PEAK DISCHARGE
- LESS RAINFALL
- DECREASE IN PEAK DISCHARGE.
(6)
How does the geology affect the risk of flooding?
- PERMEABLE ROCK
- MORE INFILTRATION
- DECREASE IN PEAK DISCHARGE
- IMPERMEABLE ROCK
- MORE SURFACE RUN-OFF
- INCREASE IN PEAK DISCHARGE.
How does having a forested land reduce the risk of flooding than having a bare land?
FORESTED LAND:
- TREES INTERCEPT RAINWATER
- ROOTS ABSORB WATER
- DECREASES PEAK DISCHARGE.
(4)
State four SOFT ENGINEERING of RIVERS.
- Flood warnings
- Floodplain zoning
- River restoration
- Afforestation.
(3)
What are the pros and cons of flood warnings?
PRO:
- people able to evacute quicker from a flooded area
CONS:
- May be inaccurate signs
- Doesnt prevent flooding.
(4)
What are the pros and cons of floodpain zoning?
PROS:
- maintains a SECURE DISTANCE
- INFRASTRUCTURE AWAY FROM RISK.
CONS:
- needs lots of ENGINEERING
- not possible to change EXISTING LANDUSES.
(3)
What are the pros and cons of river restoration?
PROS:
- Increase BIODIVERSITY
CONS:
- lots of ENGINEERING
- EXPENSIVE.
(2)
What are the pros and cons of afforestation?
PROS:
- Restores ECOSYSTEMS.
CONS:
- INVASIVE SPECIES.
(4)
State four HARD ENGINEERING of RIVERS.
- DAMS
- EMBANKMENTS
- CHANNEL DREDGING
- CHANNEL STRAIGHTENING.
(4)
What are the pros and cons of dams?
PROS:
- Controls FLOW of rivers.
- Protects settlements from TIDAL SURGES.
CONS:
- EXPENSIVE
- (farm)land becoming INFERTILE.
(3)
What are the pros and cons of embankments?
PROS:
- BLOCKS FLOODWATER
CONS:
- blocks ACCESS to water
- NIMBY-ism.
(2)
What are the pros and cons of channel dredging?
PROS:
- INCREASES CAPACITY OF WATER STORAGE
CONS:
- Removes river’s NATURAL silt –> DAMAGES NUTRIENTS.
(2)
What are the pros and cons of channel straightening?
PROS:
- protects infrastructure by SPEEDING UP river.
CONS:
- more EROSION DOWNSTREAM.
