Coasts And Rivers Flashcards
Antecedent
Weather conditions proceeding an event
Evapotranspiration
Water which is evaporated/ transpirated from plants
Water abstraction
The removing of water from aquifers
Lag time
Time between peak rainfall and peak discharge
Discharge
Water that is in a river
What is a river regime
A river regime shows how the discharge of a river varies over a longer period of time ( usually a year) being aware of factors that change the speed and amount of precipitation that reaches the river.
Thinking of a river as a system with stores transfer inputs and outputs
How are carbon and water linked in a reaction ship
Weathering, ocean warming, volcanoes, decomposition, ocean acidification, photosynthesis and respiration
What % of the worlds population now live within 100 miles of the coast
Around 50%
Factors affecting the coast
Weathering, wave type , rock types, currents/ tides, sea level , human activity, fetch, chemical acidity
Sources of energy in coastal systems- wind
Winds created by air moving from high pressure to low pressure.
Strong winds generate powerful waves. Prevailing winds causes higher energy waves than winds that change direction frequently
Sources of energy in coastal systems- waves
Waves are created by wind blowing over the surface of the sea, creating friction giving water a circular motion
The effect of the wave on shore depends on its height which is affected by wind speed and fetch of wave.
When waves reach shore they break creating friction slowing waves , creating elliptical wave.
What is the swash
Water washing up the beach
Backwash
Water washing back down towards sea
Constructive waves
Low frequency, low and long, which gives elliptical cross profile, powerful slash so deposits sediments
Destructive waves
High and steep, circular cross profile, higher frequency, strong backwash removes material from beach
Sources of energy in coastal systems- tides
Tides are the periodic rise and fall of the oceans surface, cause by gravitational pull of the moon and sun.
Tide effects the position at which waves break ( at high tide they break higher up shore)
The area between maximum high tide and low tide is where most landforms are created and destroyed
Sources of energy in coastal systems- currents
A current is the general flow of water in 1 direction
It can be caused by wind or by variation in water temp/ salinity . Currents move material along the coast
High energy coasts
Receive high inputs of energy in The form of large powerful waves- these can be caused by strong winds, long fetches and steeply shelving offshore zones.
Tend to have sandy coves and rocky landforms
The erosion rate is higher than the rate of deposition
Low energy coasts
Receive low inputs of energy in the form of small gentle waves
Often have salt marshes and tidal mudflats
Rate of deposition is often higher than rate of erosion
Inputs of sediment into coastal system
Rivers, sea level rise, eroded cliffs, offshore deposits , crushed shells of marine organisms
Waves in England
Largest waves in sw
Most erosion takes place along Yorkshire coast meaning wave type must not be leading factor of erosion in England
What ratio of wave height to wavelength does the wave break
7:1
What is energy proportional to
Wavelength x wave height is proportional to energy
Factors affecting wave strength
Wind strength , fetch, wind direction, coast configuration, wind duration
Where do waves break on smash aligned beaches
Waves break parallel with the coats
Where do waves break on drift aligned beaches
Waves break at an angle, so material is transported along the beach via longshore drift
Wave refraction at headlands
High energy waves, depth of waves decreases, waves get higher + steeper, velocity decreases, shorter wavelength, wave crest converge on headland , increasing energy therefore erosion
Refraction in bays
Low energy waves, waves reach shallower water later, waves crests diverge = lower energy= deposition , wave refraction influences rate of marine erosion like this
Wave refraction
Waves breaking into an irregularly shaped coastline ( eg headland)
Why does the ocean move
Currents, upwellings, winds.waves,tides,conveyor belt
Global ocean conveyor belt
Constant motion in the ocean. Winds drive ocean currents in the upper 10% of surface, but this also effects deep ocean currents
These deep ocean currents are driven by differences in the waters density which. Is controlled by temp and salinity, this process is thermohaline circulation.
5 types of geomorphological processes
Weathering, mass movement, erosion, transportation, deposition
Weathering
When rocks are broken down by mechanical and chemical processes caused by the weather
What does in situ mean
Not moving
Mass movement
Rock Loosened by weathering, move down slope under influence of gravity.
Chemical weathering
Acids in rain ( eg co2) can chemically dissolve rocks ( especially chalk/limestone) nitrogen and sulphur oxide can also produce acid rain
Biological weathering
Plants roots can get into tiny cracks as they grow they open these gaps wider
Dying plants also produce acid a
Burrowing animals also erode rocks
Physical ( mechanical) weathering
Water freezes in cracks as it freezes it expands this creates pressure which enlarges cracks eventually rock fall off
Rockfall
Rocks are broken down by freeze thaw weathering, this loosened material is vulnerable to the elements. Of rock is at the top of a steep cliff face it can fall directly to the shore
Mudflow
Occurs on very steep slopes along the coast line where there is limited vegetation to under the soil together and the ground is very saturated heavy rain can produce sheet flow over the upper cliff surface, the soil eventually flows over the cliff face
Landslide
When rocks and unconsolidated material on the cliff face are saturated with water and slide down slope , they occur on steep gradient and very similar to slumps
Rotational slip/ slumping
Heavy rain is absorbed by material the cliff becomes heavier and eventually sperartes from the material behind at a slip plane . Occurs on a concave cliff face
Soil creep
Movement of soil particles down a slope . The slowest type of downhill soil movement.
Gravity pulls the water contained in soil downwards which pulls soil with it . The slope may appear rippled