Rivers Flashcards
What is the hydrological cycle?
It is a continuous water system which shows how water moves around
What is evaporation?
When water is heated by the sun and turns into water vapour
What is transpiration?
The evaporation of water from plants (loss of moisture)
What is evapotranspiration?
Evaporation and transpiration happening together
Water vapour is moved inland by…
Winds
The water vapour condenses to form…
Clouds
What are transfers? E.g?
Water moving through the system
E.g surface run-off
What are outputs?
water lost when the river reaches the sea or through evaporation
What are stores?
When water is stored in lakes, rocks, soil or vegetation.
Name 3 transfers (there are 7)
- Infiltration
- Percolation
- Throughflow
- Groundwater flow
- Surface runoff
- Channel flow
Name 2 stores (there are 4)
- Channel storage
- Groundwater storage
- Interception storage
- Surface storage
What is infiltration?
When water soaks into the soil
What is percolation?
When water moves vertically down through soil and rock
What is throughflow?
When water in the soil flows downhill
What is groundwater flow?
Water going through rocks underground
What is surface run off?
Water flowing over a surface (impermeable)
What is channel flow?
The flow of water in a river
What is channel storage?
When water is held in a river
What is groundwater storage?
When water is stored underground in soil and rock.
A rock that stores water is called an…
E.g?
Aquifer
E.g chalk
What is interception storage?
When water lands on things like plant leaves and doesn’t hit the ground
What is surface storage?
When water is held in things like lakes, reservoirs and puddles
The water eventually ends up in the…
Sea
What is the one and only input?
Precipitation
What is the water table?
The upper level of underground water
What is a drainage basin?
The area of land drained by a river
The part of the hydrological cycle that happens on land goes on in…
Drainage basins
What is a water shed?
The boundary between two drainage basins - they are ridges of high land
What is the source?
Where a river starts, usually in an upland area (e.g. Mountains)
What is a tributary?
A small stream or river that flows into a larger stream or river
What is a confluence?
Where two or more streams or river channels meet
What is the mouth?
Where a river enters the sea
What is an estuary?
Part of the river which has tides usually close to the sea
What is weathering?
When rocks in the drainage basin get broken down where they are
What are the 3 types of weathering?
- Mechanical
- Chemical
- Biological
What is mechanical weathering?
E.g?
The breakdown of rock without changing its chemical composition
Freeze-thaw weathering
What is freeze-thaw weathering?
- Temp around 0°
- Water gets into cracks
- Water freezes, rock expands, pressure on the rock
- When rock freezes it cracks the rock and contracts to release pressure
- Repetition of this causes rock to break up
What is chemical weathering?
E.g?
Breakdown of rock by changing its chemical composition
E.g acid rain
What is acid rain weathering? (Corrosion)
The chemical reaction in acid water dissolves the calcium and breaks rocks down (e.g. Limestone)
What is biological weathering?
e.g?
The breakdown of rocks by living things
E.g. Plant roots
What is a river course?
The PATH of a river as it FLOWS DOWNHILL
What are the 3 different courses?
Lower (closest to mouth), middle and upper
Rivers flow in c______ in v______
Channels
Valleys
What is a long profile?
Shows you how the GRADIENT changes over the different courses
What is a cross profile?
Shows you what a CROSS-SECTION of the river looks like
What are the features of the upper course of a river?
STEEP, V-SHAPED valley, NARROW, SHALLOW CHANNEL
What are the features of the middle course of a river?
MEDIUM GRADIENT, GENTLY SLOPING valley sides, WIDER, DEEPER channel
What are the features of the lower course of a river?
GENTLE GRADIENT, VERY WIDE, ALMOST FLAT valley, VERY WIDE, DEEP channel
What are the four types of river erosion?
- Hydraulic action
- Abrasion
- Attrition
- Corrosion
What is hydraulic action?
The FORCE of the water BREAKS ROCK PARTICLES AWAY from the river channel
What is abrasion?
Eroded ROCKS picked up by the river SCRAPE and RUB against the CHANNEL, wearing it away. Most erosion happens by this process.
What is attrition?
Eroded ROCKS picked up by the river SMASH INTO EACHOTHER and break into SMALLER FRAGMENTS. Their edges also get more ROUNDED.
What is corrosion?
River water DISSOLVES some types of rock e.g. CHALK and LIMESTONE
What is transportation?
The movement of eroded material
What are the four processes of transportation?
- Traction
- Suspension
- Saltation
- Solution
What is traction?
When LARGE particles like boulders are PUSHED along the RIVER BED by the FORCE OF THE WATER
What is suspension?
When SMALL particles like silt and clay are CARRIED In the water flow
What is saltation?
PEBBLE-SIZED particles are BOUNCED ALONG the river bed by the FORCE OF THE WATER
What is solution?
DISSOLVED MINERALS carried in the water
What is deposition?
When a river DOES NOT HAVE ANY ENERGY to CARRY any material and ‘DROPS’ it
The faster the river flows, the more _______ happens
Erosion
What course of the river are waterfalls?
Upper course
How is a waterfall formed?
- The SOFTER LESS RESISTANT rock is ERODED more than the HARDER MORE RESISTANT ROCK
- This creates a LEDGE of hard rock
- A STEEP drop is created which is called a waterfall
- The HARD ROCK is eventually UNDERCUT and COLLAPSES
- Erosional processes like abrasion happen at the foot of the waterfall, this is called a deep PLUNGE POOL
- The water fall RETREATS, leaving behind a GORGE
What course of the river are interlocking spurs found?
Upper course
What are interlocking spurs?
When the vertical erosion isn’t powerful enough to erode sideways so they wind around the hillsides like a zip
What are meanders?
Large bends in a river
What 2 courses of the river do meanders develop?
Middle and lower courses
How are meanders formed?
- When the CURRENT is faster on the OUTSIDE of the bend because the river channel is DEEPER (LESS FRICTION AND MORE ENERGY)
- So more EROSION takes place on the OUTSIDE of the bend, forming RIVER CLIFFS
- So more eroded material is DEPOSITED on the INSIDE of the bend, forming SLIP-OFF slopes
What are Ox-bow lakes formed from?
Meanders
How are oxbow lakes formed?
- When the outside bends get closer and closer until there’s only a small bit of land left between the bends (NECK)
- The water breaks through, the river flows the SHORTEST ROUTE
- DEPOSITION eventually cuts off the meander, forming an oxbow lake
What are flood plains?
Flat areas of land that flood - they are the WIDE VALLEY FLOOR that gradually builds up as more eroded material is transported
What are levees?
Natural embankments (raised bits) along the edges of a river channel
How are levees formed?
During a flood, when eroded material is deposited over the whole flood plain. The heaviest material is deposited closest to the river channel. Therefore creating raised edges
What is a delta?
Where a river meets the sea and slows down, therefore drops its load causing land to form in different shapes
What are the three types of delta and a short description?
- Arcuate - have a rounded shape and lots of distributaries
- Cuspate - have a triangular shape and few distributaries
- Birds foot - like a birds foot!!
What is lateral erosion?
Erosion of the sides of a valley
What is vertical erosion?
Downward erosion of a river bed
What is river discharge?
The VOLUME OF WATER that flows the river PER SECOND?
What is river discharge measured in?
Cumecs (cubic metres per second)
What is a storm hydrograph?
They show how a river will act after heavy rain
Revise the appearance of a storm hydrographic
.
What is the peak discharge?
The HIGHEST DISCHARGE in the period of time you’re looking at
What is lag time?
The delay between PEAK RAINFALL and PEAK DISCHARGE
What is the rising limb?
The INCREASE in river discharge as the rainwater flows into the river
What is the falling limb?
The DECREASE in river discharge as the river returns to its NORMAL LEVEL
What is the base flow?
The EXPECTED discharge for the time of year
If more water flows as surface runoff the lag time will be…
Shorter
What are 3 factors that increase discharge and make the hydrograph steeper? (6)
- High rainfall
- Intense rainfall
- Impermeable rock
- Previously wet conditions
- Steep slopes
- Vegetation
What are 3 factors that decrease discharge and make the hydrograph less steep? (6)
- Low rainfall
- Light rainfall
- Permeable rock
- Previously dry conditions
- Gentle slopes
- More vegetation
Urban areas are likely to have steep or not steep hydrographs? Because??
Steep because they have drainage systems and are covered with impermeable materials
Rural areas are likely to have steep or not steep hydrographs? Because??
Not steep because they have more vegetation and more reservoirs
Rivers flood due to many physical factors. Name and describe 3 (5)
- Prolonged rainfall
- Snow melt (when ice melts fast)
- Geology (more impermeable rock)
- Heavy rainfall
- Relief (how the height of the land changes)
Rivers flood due to a few human factors. Name and describe the 2 main ones.
- Deforestation
* Urbanisation (more impermeable surfaces and buildings)
What are 2 serious impacts on people as a result of a flood (4)
- People killed
- Buildings and roads are damaged or destroyed
- Jobs are lost
What are hard engineering techniques?
Man-made structures built to control the flow of rivers and reduce flooding
What are soft engineering techniques?
Schemes set up using knowledge of a river and it’s processes to reduce the effects of flooding
Name 2 hard engineering techniques used to prevent flooding (3)
- Dams and reservoirs
- Channel straightening
- Man-made levees
Name 2 soft engineering techniques used to prevent flooding (3)
- Flood warnings
- Preparation
- Flood plain zoning
What is channel straightening and how does it help?
When a Rivers course is straightened e.g taking out meanders so the water doesn’t have to travel as far
What are dams and reservoirs?
Huge walks across the river to store water and release it slowly
