1a.Coastal landscapes viewed as systems
● System is a set of interrelated objects comprising components (stores) and processes (links) that
are connected together to form a working unit.
Components including inputs, processes and outputs:
● Inputs- lead to processes
- Marine: tides, waves, salt spray
- Atmosphere: sun, precipitation, air pressure, wind speed and direction
- Humans: pollution, recreation, settlement, defences
- Terrestrial: weathering, erosion, deposition, rock type/ structure
● Processes- lead to outputs
- Erosion
- Transport
- Deposition
● Outputs- landforms/ features
- Beaches
- Sand dunes
- Spits
- Bars and tombolos
- Headlands and bays
- Cliffs
- Wave Cut notches
- Wave Cut platforms
- Caves
- Arches
- Stacks
- stumps
Flows of energy and material through coastal systems:
● Store and transfer energy and material on time scales that can vary from a few days to a millennia
● Energy- may be kinetic, thermal or potential (gravitational)
- Kinetic energy from wind and waves
- Thermal energy from heat of the sun
- Potential from position of material on slopes
● Provided by waves, winds, tides and currents
● This energy enables natural geomorphic processes that shape
● Varies spatially and temporarily
● Material-
- System- sourcing, transfer and deposition of sediment along stretch of coastline called a
sediment cell (-not on advanced but discussed below)
● Coastal systems known as open systems- energy and matter can be transferred from neighbouring
systems as an input. It can also be transferred to neighbouring systems as an output
● When systems input=output, equilibrium exists
● Sediment cell stretch of coastline associated
nearshore area within which the movement of
coarse sediment, sand and shingle is largely
self-contained- closed system
,1b.Coastal landscape systems are influenced by a range of physical factors
Winds, including speed, direction and frequency:
● Source of energy for coastal erosion & sediment transport
● Through aeolian processes or through this energy being transferred to wave energy
● Aeolian transport and deposition is responsible for the formation of sand dunes
Waves:
● Waves created by frictional drag of wind blowing over the surface of the
sea, wave energy depends on-
- Wind strength
- Wind duration
- Water depth
- The fetch of the wave
● Wave dominated coasts- sandy and rocky coastlines
● Dynamic and sensitive systems, often in equilibrium in natural
state, but susceptible from interference of human activity
● Global scale coastal environments reflect large degree the climatic
conditions experienced in a region such as wind speed and duration, as well as size of the ocean
concerned
● Deep ocean-sea/force waves
● As they propagate out of area of generation they become swell waves (oscillatory waves)
● They have an oscillatory motion, water particles do no more, just energy
● ¼ wavelength in terms of depth of water= wave base
● When the wave base intersects the seafloor, the wave shoals/ breaks and becomes a translatory
wave
● Translatory wave transfer both energy and water
● Wave formation, development & breaking
- Spilling breakers (constructive)- gentle beach gradients, high steepness waves, bubbles
and foam
- Plunging breakers (destructive)-
- Surging breakers-
● Wave refraction- waves encounter vertical face of sea wall, may approach 100% (L3)
● Wave refraction during shoaling
● Wave approaches irregular coastline, part of wave that is in shallower water travels more slowly
than the part of the wave in deeper water causing wave to bend
● Refraction can create longshore currents such as longshore drift
,
,Tides, tidal cycles and range:
● Tides are cyclical and
predictable
● Periodic rise and fall of
sea surface produced by
gravitational pull of the
moon and lesser extent
the sun
● Often significant in
development of coastal
landforms
● Affected by factors such as
- Variations in ocean
depth
- Topography of sea
bed
- Shapes of continental land masses
● Only some coastal environments said to be tidal dominated (-mainly estuaries)
● Most coasts experience 2 high tides and 2 low tides per day (semi-diurnal tides)
● High and low water are separated by approx 6 hours and 13 mins, high and low water occur slightly
later each day
● How to calculate tidal range: mean tidal range is calculated as the difference between Mean High
Water (i.e., the average high tide level) and Mean Low Water (the average low tide level)
Global pattern of ocean currents:
● Nearshore and offshore currents have an influence on coastal landscape systems
● Rip currents play role in the transport of coastal sediment through tidal motion or waves breaking at
right angles, (rip currents modify shore profile by creating cusps which perpetuate rip current)
● Cellular circulation generated by differing wave heights parallel to the shore
● Ocean currents larger scale generated by Earth’s rotation and by convection, set in motion by
movement of wind across oceans surface
● Warm ocean currents transfer heat energy from low lat towards poles
● Particularly affect western-facing coastal areas when driven by onshore winds
● Cold ocean currents move cold water from polar regions towards the equator, driven by offshore
winds have less effect on coastal landscapes
● Strength of the current itself may have limited impact on systems but the transfer of heat energy
can directly affect air temp, and sub-aerial processes (-collective term for weathering and mass
movement
processes)
,1c.Coastal sediment supplied from various sources
Terrestrial:
● Origin from inland erosion by water, wind, ice + sub-aerial processes
● Erosion of area such as weak cliffs, and high energy coastlines transfer sediment from one terrestrial
location, to in some cases another
● Sediment budget- balance between sediment added and removed from coastal system
● More added than removed= surplus and build up of shore seaward
● More material removed than added= deficit
Fluvial deposition:
● Rivers major source of sediment input to sediment budget
● True of coasts with steep gradient, rivers directly deposit their sediments at the coast
● Sediment delivery to the shoreline can be intermittent mostly occurring during floods
● Some locations 80%+ coastal sediment comes from rivers
Marine erosion:
● Wave erosion also large source
● Rising sea levels +storm surges amplify frequency and magnitude of erosion
● Erosion of weak cliffs in high energy environments contributes to as much as 70% of material
supplied to beaches
Longshore drift:
● Can also supply sediment from one coastal area by moving it along the coast
to adjacent areas
Offshore-Aeolian deposition:
● Wind blows sediment from other locations including exposed sand bars,
dunes and beaches elsewhere along the coast
● Generally fine sand, wind less energy than water and cannot transport large
particles
Offshore- Marine deposition:
● Constructive waves bring sediment to the shore from offshore locations and deposit it adding to the
sediment budget (tides+currents do the same)
Human:
● Coastal sediment budget in deficit one way to restore/ maintain equilibrium is through beach
nourishment-sediment dumped and/or deposit with water onshore by pipeline from offshore sources
- Low bunds hold the mixture in place while the water drains away leaving sediment behind
● Calculating sediment
budget- subtracting
amount of sediment
lost from sediment
gained, can be
determined if in
surplus, deficit or
equilibrium
𝑠𝑒𝑑𝑖𝑚𝑒𝑛𝑡 𝑙𝑜𝑠𝑡 − 𝑠𝑒𝑑𝑖𝑚𝑒𝑛𝑡 𝑔𝑎𝑖𝑛𝑒𝑑 = 𝑑𝑒𝑓𝑖𝑐𝑖𝑡, 𝑠𝑢𝑟𝑝𝑙𝑢𝑠, 𝑒𝑞𝑢𝑖𝑙𝑖𝑏𝑟𝑖𝑢𝑚
, 2.How are coastal landforms developed?
2a.Coastal landforms develop due to a variety of interconnected climatic and geomorphic processes
Erosional landforms
Cliffs:
● Destructive waves break repeatedly on steeply sloping coastlines, undercutting can occur between
high and low tide levels where forms wave cut notch
● Continued undercutting
weakens support for rock
strata above, collapse
producing steep profile and a
cliff
● Regular removal of debris at
foot of cliff
● Cliff retreat inland parallel to
the coast
● Vary depending on geology-
higher the more undercut, collapse and retreat continues
● Horizontally and landward dipping rock strata support cliffs with steep, near vertical profile
● If rock strata inclines seaward, profile follows angle of dipping strata
Shore platforms:
● At its base a gently sloping shore platform cut
into solid rock
● Predominantly formed by erosion, weathering
processes also important in their development
● Usually slope seawards at an angle between
0° and 3°
● Constant water levels between high and low tide erosion greatest at this point
● Formation of ramp at high tide level and small cliff at low tide level- tidal range<4m
● If tidal range is higher erosion spread over wider area of platform for shorter time more uniform and
more steeply sloping
Geos and Blowholes:
● Geos (1) are narrow, steep sided
inlets, lines of weakness such as
joints and faults eroded more rapidly
by wave action than resistant rock
around them
- Geos can initially form as
tunnel-like caves running at
right angles to the cliff line, as
they become enlarged may
suffer from roof collapse
creating a geo
● Blowhole (2)- part of the roof of a
tunnel-like cave collapses forming
vertical shaft that reaches cliff top
Caves, Arches, Stacks and Stumps: ->
