Coastal Processes and Landforms Flashcards
Which country has the longest coastline?
- Canada, tops number 2 by almost 5x! (much of it is undeveloped and in the Arctic)
- Followed by Indonesia (number 2), Greenland, Russia, Philippines etc.
How much of the worlds and North America’s population lives on the coast?
- 2.2 billion globally
- 75 percent NA
How much coast does BC have?
- 22000km
Dynamic environment of the coastal/littoral zone
- Interaction btwn terrestrial, atmospheric, and marine systems (solid, liquid, and gas processes)
- Energy from winds, waves, and tides (very dynamic)
- Rapid responses btwn process and form, continually changing
Spatial and temporal variations of coastal/littoral zone
- Extensive zones spanning km’s from wave break to back shore (include inlets, fjords etc.)
- Forms and processes change w/ season, storms, tide range, sea-levels
Coastal landforms change short-term with?
- Seasons
- Storms
- Tides
- Land characteristics
- Human alterations
What are some examples of human alteration of coastal landforms on the short-term scale?
- Offshore: groins, sea walls
- Onshore: deforestation, etc.
Coast landforms change longer-term with?
- Tectonics, subsidence, uplift
- Sea level change, transgression, regression
- Delta progradation
- Glaciation
- Land changes (river i/p, volcanic eruptions
What percent of the worlds coastline is sandy?
- 34 percent
- popular for tourism, development, ecologically distinct
- Ever-changing, responsive to coastal processes
What kind of coastline is highly responsive to coastal processes?
- Sandy
- Ever-changing
What makes for a beach?
- Competent wind/wave/tidal processes and sediment supply and ‘accommodation space’
Allochthonous
- Externally sourced
- 92 percent globally
- Mostly from rivers, aeolian, glacial, colluvial w/ some offshore sources
Autochthonous
- Locally derived
- 8 percent globally
- Biogenic sediments, carbonate rich beaches, local shoreline erosion
Coastal system landforms and zones
- Different parts of the littoral zone exhibit diff wave and current processes to create a suite of related landforms
- eg longshore currents: shore parallel current caused by wave action in the nearshore region w/in the breaker zone
Schematic of longshore currents and beach
- Offshore, nearshore, shore, coast
- Beach composed of nearshore and shore
- Shore composed of foreshore (low to high tide) and back shore (where tide doesn’t reach)
- Breakers in nearhore
- Longshore bar, longshore trough, wave-cut bench, beachface, berm, notch, wave-cut cliff
Where are beaches wider? Narrower?
- Further from erosional zone = wider, closer = narrower
- Broad, can also get dune systems from wind blowing seds back towards land
Greenwich dunes, PEI
- Sed being limited by strong wind regime
- Fastest eroding shorelines in Canada (1-3m/yr)
- Isostatic collapse/ sea rising 30cm/100yrs
- Huge dune systems from strong wind regime liberating sediment
Human made rock berms
- Meant to protect coast (e.g. highway in Haida Gwaii)
- Reflect energy back but can combine w/ incoming waves to generate positive feedback
- Feed back amplifies undercutting and erosion
- Also stronger rip and longshore currents
- Normal function: wave energy used in swash and sed transport
What is another/maybe better way of protecting human infrastructure on the coast?
- Build wider beaches so natural function of swash and sed transport can happen
- But building groins to do this starves beaches further down of sed
- Therefore more and more groins get built
Time-space paradigms in coastal study
- Geological w/ Net shoreline
- Large-scale (engineering) w/ large size beach cycles, major storm erosion
- Events w/ seasonal beach cycles
- Instantaneous w/ ripple migration
Geological time-space paradigm
- Geological: net shoreline, net shoreline movement
- on Millenia-century scale
- w/ climate change, tectonics, sea level, sediment supply
Large-scale (engineering) time-space paradigm
- Large-scale (engineering): Net shoreline movement (horiz), large size beach cycles, major storm erosion, beach position
- on century-decade-year scale
- w/ Sed supply, wave-climate cycles, annual wave climate tidal regime
Events time-space paradigm
- Events: beach position, seasonal beach cycles, beach migration beach face
- on yr-season-months-days scale
- w/ annual wave climate tidal regime, seasonal wave climate, tide cycles storm events, wave trains
Instantaneous time-space paradigm
- Instantaneous: beach migration, beach face, ripple migration, ripples
- on day-hour-seconds scale
- w/ wave trains, tide, waves
What are the 5 main factors that influence coastal geomorphology?
- Climate (temp, evapotrans, precip)
- Sediment budget (sources of erosion and transport, sinks)
- Human activities (construction, alteration)
- Relative sea level (tectonic subsidence, compactional subsidence, eustatic changes, secular changes)
- Coastal processes (waves, currents, tides, wind, storms, river discharge, valley aggradation or incision
The coastal system and the time element?
- Shorface affected by shoaling, breaking waves, and swash
- At scales from millennia to instantaneous
- Each produces characteristic bed response and are linked through time and space by morphodynamic couplings
Coastal processes: forces w/in the liquid realm, Waves
- Formed by drag of wind over sea
- Dominant energy transfer process
- 2 types: Deep water waves of oscillation and Translational waves
Coastal processes: forces w/in the liquid realm, Tides
- Due to gravitational forces of moon and sun
- Locally interact w/ bathymetry
- Important where coastal configurations enhance tidal ranges and currents (e.g. bay of fundy)
Coastal processes: forces w/in the liquid realm, Nearshore currents
- Caused by winds and tides
- Also driven by heat and density variations, Coriolis
Coastal processes: forces w/in the liquid realm, Winds
- Onshore transport of littoral sediments
Coastal processes: forces w/in the liquid realm, Long-term ‘relative’ sea level changes
- Function of eustatic, tectonic, temperature effects etc.
Wave development
- Formed by wind shear on water surfaces
- As waves grow, become higher, wider, faster
- Feedbacks btwn roughness, wind energy and wave growth
Wave growth
- Micro-ripples to ripples to chop to fully developed sea (fds)
Wave growth w/ increasing wind and fetch
- Micro-ripples to ripples to chop to fully developed sea (fds)
Max size of waves
- Function of wind speed, duration and fetch
- Need all 3 for giant waves
- Eg 111km/hr (60knots) wind of unlimited fetch produce 15m waves
Perfect storms
- Atlantic winds > 100km/hr for several days over 1000’s of kms
- Produce the largest waves, >30m, highest record is 34m
Wave parameters
- Wavelength, dist btwn 2 peaks
- Height, btwn trough and crest
- Period, Time required for wave crest at one point to reach next point
Wave processes: deep water, waves of oscillation
- Water particles assume a circular orbital path w/ little forward motion
- Wavelength, L (m) = (gravitational acceleration x Period^2) /2pi
- Velocity/Celerity (m/s) = (g x Period)/2pi
Wave period
- T
- Time btwn passing wave crests
- Easily measured, proportional to both wavelength and velocity
Open Ocean waves
- Deep water, waves of oscillation
- Generated by strong steady winds blowing across long open fetches
- Wind stress causes water surface to deform into ripples, chop, then waves
- Waves from shifting winds combine to develop many frequencies in a typical wave spectrum (these show diff wavelengths and energies)
Wave dispersion
- Waves move from generation area, separate from one another due to travel speeds (big outrun small)
- Emerging waves more regularly spaced, low height to length ratios, low steepness, referred to as swell
Swell waves
- Emerging waves more regularly spaced, low height to length ratios, low steepness, referred to as swell
- Long periods, eg 100 seconds
- Follow directional pathways defined by dominant storm wind directions
Ocean swell cover’s how much area?
- Cover large areas of ocean
- But has finite lateral boundaries, so strikes along short sections of coastline (10’s of km)
How far can ocean swell travel?
- Can travel 100’s of km w/o much energy loss
- Most energy loss occurs in short period waves that dissipate in the generation zone into the longer period swells
Two sets of swell from different sources may combine to create?
- May combine into a systematic variation in wave height known as ‘surf beat’
- Successive waves increase in height to a max, then systematically decrease
- Large waves may appear w/ predictable regularity (often every 6-8th wave but depends on wave periods and harmonics)
Shallow water shoaling and waves of translation
- Shoaling occurs as deep waves approach shoreline
- Begin to interact w/ ocean bottom
- Occurs when water depth is approx have the wave length
- Deep water become shallow water waves, transfer energy to the bed, particle orbits become flattened into ellipses
- Top oscillating water column starts tipping forward and flattening, eventually waves oversteepen and break
- Wavelength decreases and height increases
Waves of translation, what is the significance to sediment maintenance?
- Waves shoal, water particles develop forward motion critical to sediment maintenance on beaches and near shore areas
- W/o shoreward asymmetry, sands would move offshore and expose shoreline to erosion
Production of waves of translation and shoaling
- Water shallows, waves increase in height, decrease in wavelength and velocity
- Crest bunch up
- Wave period remains constant
- Waves break when wave height/length >1:7
- Oscillatory waves are replaced by a completely different wave type called ‘Waves of Translation’
Waves of translation and geomorphology
- Transformation to shallow translational waves applies geomorphic work on bed
- Effective limit of wave influence on the bed is known as wave base (occurs when H/L = approx. 0.5)
- Greatest influence where waves break
What happens to wave parameters once waves become translational?
- Velocity and length are proportional to water depth (h)
- L = Period x sq. root g x h
- V = sq. root g x h
Types of breaking waves
- Spilling
- Plunging
- Collapsing
- Surging
Long durations and sustained winds =
Increase in wave amplitude
Spilling waves
- Breakers occur on gradual slopes w/ flat beaches
- Takes several wavelengths to break
- Turbulent whitewater spills down face of wave
- Minor energy impacts on bed
Plunging waves
- Breakers occur on steep slopes or at sudden depth changes (e.g. on reefs or sandbars)
- Break w/in a couple of wavelengths concentrating energy and causing significant scour
- Wave crest much steeper than spilling wave
- Curls over and drops onto wave trough releasing most of its energy at once in a relatively violent impact
- Active in shoreline erosion
Collapsing waves
- Breakers are intermediate btwn plunging and surging
- Crest never fully breaks
- Bottom face of wave gets steeper, collapses
- Results in foam
Surging waves
- Breakers occur on steep beaches but waves have low steepness
- Wave crests remain unbroken but wave base surges up the beach w/ smooth, sliding motion
- Causes crests to collapse and disappear
Shoaling zone
- Waves begin to feel bottom and increase in height
- Offshore, coarser sediment trends, accretionary actions, better sorting, increasing energy
Breaker zone
- Waves break and forward translation begins
- Wave collapse, coarsest grains, erosionary actions, poor sorting, high energy
Surf zone
- Forward translation (bores) continues
- Longshore currents, seaward return flow, rip currents
- varied sediment trend, transportation action, mixed sorting, energy gradient increasing to collision zone
Swash zone
- Swash and backwash in foreshore
- Collision and transition to swash zone
- Coarser sed towards bi-modal lag deposit in collision zone
- Accretion and erosion, poor to better sorting towards beach
- Highest energy in collision/transition zone, decreases to swash and beach zone
Wave energy spectrum
- Longest period to shortest: Tidal-Tsunami-Surf beat/seiches-wind waves-ripples
Wave energy is a function of?
- Amplitude/magnitude and frequency
Tidal waves
- Longest period, hours to days
- Due to Gravity force
Tsunami/Seismic sea waves
- Long period, not as long as tidal
- low in ocean
- Due to seismic disruption, landslides
Seiche waves
- Oscillating water levels in enclosed basins (e.g. lakes)
- Surf beat
- Restoring force = gravity
Capillary waves/ ripples
- Shortest period (up to 100/s)
- Restoring force = surface tension
Instruments for measuring waves
- L, offshore buoy: wind, pressure data and wave parameters
- C, Acoustic doppler current profiler (upward radar): wave parameters
- R, Wave staff: water level
- Etc. Many more types
Frequency distribution of wave heights
- Skewed to left, more of smaller height, median less than mean
- Significant wave height then 90th percentile
Significant wave height, Hs
- Mean wave height of the highest 1/3 of waves
Nomograph
- Wave height-fetch relations
- Uses wind speed and duration to determine wave period (dashed line)
- Uses wind speed and fetch to determine significant wave height (solid line)
Coastal wave modification
- Along coasts, bottom topography and shoreline variations cause major changes to wave geometry and mechanics
- Product of transformations is geomorphic work applied to sea floor, beach and shoreline
Coastal wave modification transformation types
- Wave refraction
- Wave diffraction
- Wave reflection
- Wave shoaling
Wave Refraction
- Waves usually approach coast obliquely
- Shorten wavelength when encountering bottom, changes velocity, waves bend and refract towards shore
- Waves closer to shore slow down, outer waves move faster
- Results in bending of waves (refraction) and focusing wave energy more directly onshore
- Wave energy moves at right angles to wave crests
Wave Refraction results on geomorphology
- Focuses wave energy on headlands
- Dissipates energy in embayments (btwn headlands)
- Tends to flatten shorelines over time
- Resistant bedrock outcrops can inhibit even focused wave erosion
What is the result of seawalls and refraction?
- Seawalls aren’t the best b/c they refract waves
- Focus energy
- Results in more erosion than prior to construction
Diffraction waves
- Transfer of energy along wave crest and occurs around obstacles
- Can lead to waves crossing directions, creating navigation hazards
- Waves on waves, continue patter w/o merging
- Either enhanced or diminished erosion
Breakwaters and Tombolos
- Breakwater diffracts waves and can help dissipate energy, reduce rip currents, prevent erosion, widen beaches
- Build tomoblos in low energy back section of breakwaters
- Breakwaters better when not very large/massive
Reflection Waves
- Waves impacting cliffs, steep beaches or vertical barriers (seawalls) often reflect waves back to sea
- Interactions btwn incoming and outgoing waves create constructive or destructive interference
- Significant effects on bedforms and bottom topography
- Coarse beaches can be reflective
Tides
- Essentially very long waves generated by gravitational attraction of mood and sun
- Magnitude varies w/ moon/sun alignment and proximity
- Regular/predictable periodicity
Tide periodicity
- Usually 2x daily
- High-high, high-low, low-high, low-low
- Moon phases generate spring-neap tidal cycle
What is the timing and amplitude of tides influenced by?
- Alignment of sun and moon
- Pattern of tides in deep ocean
- Shape of coastline and near-shore bathymetry
Where are the highest tides in the world found?
- Bay of Fundy
- 16.3m
Beach type based on tidal range
- Microtidal to macrotidal
- Most of BC is in macro tidal range, but varies considerably
Cause of tides
- Gravitational interactions w/ sun and moon
- Moon 2x as strong
- Opposing tidal bulges
- Spring when sun and moon in line, highest tides (full and new moon)
- Neap, lowest tides, when sun and moon 90 degrees from earth, opposing bulges (1st and 3rd quarter moon)
Tides as geomorphic agents
- Significant agent b/c involves enormous water quantities
- Tides change location of wave action, = geomorphic work
- Tides rise and fall faster in open ocean than coastal inlets, results in surface gradient, produces strong inward-flowing currents, transports sed
Geomorphic relevance of tides
- Tides alter focus of wave action, surf and swash, e.g. tidal terraces
- Flood/ebb tides influence sed transport direction and quantity, e.g. flood/ebb deltas
- Enhanced coastal erosion and sed transport if timing combines w/ storm surge and/or waves
What are the 3 basic types of tides?
- Semi diurnal w/ 2 highs and 2 lows, often 1 higher high and 1 lower low
- Mixed tides w/ mix of semi-diurnal and diurnal
- Diurnal w/ 1 high and low
Why do some places have higher tides than others?
- Tides are waves, when encounter shoreline, get higher
- eg Oak bay is protected inlet, energy peak not high, therefore lower tides
- Inlets w/ tidal waters funnelled (Port Alberni, Bay of Fundy), tidal waves greatly amplified
Tidal range
- High tide to low tide
- Local ranges highly variable depending on ocean size, water depth, bathymetry, shoreline shape, currents, timing
Tides and storm surges
- Enhanced water levels occur in storm surges, can be deadly
- Due to combined effects of wind stress, pressure drop, and/or temperature
- 1mb drop results in 1cm rise in SL
- Enhanced during el nino seasons (warmer = stormier)
Tidal influence on coastal landforms
- Considerable effect
- Macrotidal = higher tide ranges, shore-normal currents, wide salt marshes and tidal flats, large ebb and flood sed inputs
- Microtidal and lower mesotidal = barrier islands, tidal deltas, high energy and the sediments get remobilized
Esquimalt lagoon - Coburg peninsula
- Barrier spit complex
- Microtidal range
Tidal dunes
- Evidence found near Victoria
- Indicates very high energy
- Very large amplitude dunes
What are the 2 main types of nearshore currents
- Cross-shore, ie rips
- Longshore, unidirectional
- Both affected by tidal stage
- Combine to form nearshore circulation cells that span m to kms of coast
Cross-shore rip currents
- Controlled by bottom topography in surf zone, especially bars, and troughs parallel or sub-parallel to shoreline
Longshore currents
- Uprush/swash in thin sheet moving sediment onshore in direction of wave, oblique to shore
- Some water sinks, some washes down beach face, moving sed as slope-normal backwash (90 degree to shore)
- Net result is beach drift
Beach drift
- Result of longshore current
- Primary mechanism for movement of sediment along the shore face
What are the best results for quantifying nearshore currents?
- Best results use momentum analysis
- Momentum, unlike energy, is preserved as waves break and separates into shoreline parallel and shoreline normal components
- Good estimate of longshore current velocity at midsurf is V = 2.7um sin alpha cos alpha
- Where um is max orbital velocity at breaker zone, alpha = breaker angle of incidence w/ shoreline
Bed shear stress
- Like fluvial
- Bottom boundary layer, friction generates small turbulent vortices
- Set up stresses between fluid and grains
- = Fluid density x Horizontal turbulent velocity x Vertical turbulent velocity
- Not used until recently, older methods exist
Alternative method for quantifying nearshore sed transport
- Use friction factor and free stream velocity above boundary layer
- = 1/2 fw x u^2
- ks is bed grain roughness, used to calculate fw
- D is mean sed size, A is orbital amplitude defined by wave period
- Parameterizations done in lab settings w/ fixed beds, not great analogues
2 dominant approaches to swash zone sediment transport
- Meyer-Peter and Muller
- Bagnold (1963)
- Needs calibration coefficients, mean flow velocity during 1/2 swash cycle, duration of 1/2 swash cycle, friction angle of sed, beach gradient etc.
Calibration coefficient for swash zone sed transport
- Not well understood
- ‘Fudge factor’
- Take empirical data to calculate but doesn’t work
- Needs a calibration factor to make work
- Main consistency is that k is larger for uprush vs. backwash, which matches empirical data
Longshore sediment transport, littoral drift
- Shore-parallel movement of sediment on upper shore face
- Rates generally much larger than cross-shore/rip transport rates
- Typically unidirectional, mainly current driven
- Straight, uninterupted shorelines have very high longshore transport
- On the order of 1 million cubic m/yr
Littoral drift eqn
- Inman and Bagnold, 1963
- Q mu K’Hb^2V
- Where Q = longshore volumetric transport rate (m^3/a), K’ = constant of proportionality (0.08 - 2.2), Hb = breaking wave height (m), V = longshore current velocity (m/s)
Factors affecting nearshore transport (5)
- Fluid velocity
- Grain size and sorting
- Bedforms
- Wave groups
- Wave breaking
Fluid velocity (nearshore transport)
Typically higher u” from waves and/or currents
Grain size and sorting (nearshore transport)
- Sediment fall velocity
Bedforms (nearshore transport)
- eg turbulence from ripples enhances bed shear and vertical mixing
- Bars create feedback
Wave groups (nearshore transport)
- ‘pumping up’ of sed concentrations toward end of larger wave groups
Wave breaking (nearshore transport)
- Additional turbulence and vertical mixing w/ bed
- Turbulence can enhance bed shear, reduces velocity, makes shallower
- eg vortices under plunging breakers vs. spilling breakers
Beach state, 2 end members
- Fully Dissipative
- Highly Reflective
Fully dissipative beach state
- Flat, shallow beaches w/ relatively large subaqueous sand storage
- Spilling breakers occur
Highly reflective beach state
- Steep (> 6 deg) beaches w/ little subaqueous sand storage
- Waves plunge and dissipate energy
How do tidal cycles influence wave state?
- Tides shift position of swash, surf, and shoaling waves zones
- Pronounced effects on water circulation, rips and undergo are stronger at low tide
- Rule of thumb: as wave height increases, Dimensionless fall velocity and Surf-scaling parameter increase, Relative Tide Range (RTR) decreases
What are the 3 ways that beach state is defined?
- Dimensionless fall velocity
- Surf-scaling parameter
- Relative tide range RTR
Dimensionless fall velocity, omega
= Hb/sed fall velocity x T
- Hb breaking wave height, sediment fall velocity, Wave period (T)
- < 1 reflective, >6 dissipative
- Function of grain size and wave characteristics
- Decreases w/ smaller grain sizes
Surf-scaling parameter, epsilon
- Differentiates effects of different kinds of waves
- requires Hb - breaker height, Wave period, Beach gradient
- < 2.5 = reflective, >20 = dissipative
Relative Tide Range, RTR
= TR/Hb
- TR = mean spring tide range
- Hb = breaking wave height
Wave dominated beaches
- RTR < 3
- Dissipative: Dimensionless fall vel >6, Surf-scaling >20
- Intermediate: fall vel 2-5, surf-scaling 2.5 - 20
Reflective: fall vel <1, surf-scaling <2.5
Tide-modified beaches
- Typically RTR = 3-10
- All: RTR = 10-50, fall vel <2
- Reflective and low-tide terrace: fall vel <2
- Reflective and low-tide terrace and bars and rips: fall vel 2-5
- Ultra-dissipative: Fall vel >5
- Mud flats: RTR >50
Dissipative beaches
- High waves, wide surf zone, wide flat beach, low mobility
- Max aeolian and wave induced sediment transport
- Large, high foredune
- Extensive holocene barrier development
- Commonly extensive parabolic or transgressive dune fields
- Flat to concave beach face, parallel bars and troughs, spilling breakers
Intermediate Beaches
- Low to high waves, narrow to wide surf zones, berms wide, flat beach, high mobility
- Moderate aeolian and wave induced sediment transport
- Small to large, low to high foredune
- Small to extensive holocene barrier development
- Narrow foredune plain to extensive parabolic dune fields
- Wrack line, berms and megacusps, crescentic bars and rips, plunging breakers
Reflective Beaches
- Low waves, narrow surf zone, steep beach, low mobility
- Minimal aeolian and wave induced sed transport
- Small, low foredune
- Limited holocene barrier development
- Commonly narrow relict foredune plain
- Cusps, steps, linear near shore zone, surging breakers
Seasonality and beach form
- Low waves in summer can bring sed onshore
- Winter storms w/ larger waves move sed offshore, results in more gravelly coarse beach
Erosional landform features: 3 categories
- Headlands and bays
- Caves, arches, stacks
- Cliffs, wave cut platforms
Erosion of a headland
- Weak areas attacked by waves, opened to form cave due to erosion and hydraulic action
- Cave widened and deepened by erosion, forms an arch
- Roof of arch is undercut, eventually collapses, leaves isolated Stack
- Stack eroded, becomes a Stump
Depositional landforms
- Spits
- Barrier islands
- Tombolos
- Nearshore bars
- Bay barriers, lagoons (behind barriers)
Spits
- Long, shore parallel extension of land
- Attached at one end to mainland coast
- Build by waves and longshore currents
- Can form in any tidal range
- Can be hooked or ‘recurved’
- Deflection along longshore drift zone, sends out from shore and deposits sed in long bars
Barrier Islands
- Long, shore parallel island
- Not attached to mainland coast
- Build by waves and longshore currents
- Micro-meso tidal envrs
- Separated by shallow bays, lagoons, or sounds
- Often in chains that extend for 100 plus km
- Extensive in E Canada down to Florida
- Beaches can lead to flood and ebb deltas
Tombolos
- Wave diffraction around an island
- Sediment builds up behind island, can connect island to mainland shore
- Typically moderate to low wave energy
Nearshore bars
- Nearshore and intertidal shore parallel, asymmetric features
- 0.25-4m high, 25-150m wide, 50m-km long
- Formed by convergence of onshore transport due to shoaling and breaking waves, w/ undertow near bed
- Bars migrate during storms (dynamic envr)
- Straight bars, transverse bars, inner bars, outer bars, crescentic bars
4 Characteristic profile forms
- Nonbarred
- Barred
- Alternating
- Tidal influenced
Nonbarred profile form
- Smooth, planar to curvilinear
Barred profile form
- 1 or more bars
- Associated troughs
- Year round
Alternating profile form
- Alternating barred and nonbarred
- Often seasonally
Tidal influenced profile form
- Semi-permanent bars in intertidal and subtidal zones
Summary of Coastal processes
- Coastal zone is interface btwn water bodies, atm, and lithosphere, therefore highly dynamic
- Coastal processes consist of waves, tides, currents, and sediment transport processes and models
- Depositional forms consist of spits, bars, barriers, tombolos etc.
- Beach energy regimes consists of RTR, surf similarity, fall velocity and result in wave-to-tide-dominated beaches
- Erosional landforms consist of arches, stacks, caves, platforms, stumps, etc.
Coastal zone consists of?
- Interface w/ lithosphere, atm, and water
- Offshore, nearshore, foreshore, and backshore
- Extends several km from point of wave break to back shore
- Forms and processes vary over tides, events (storms), seasons, interannually, longer term RSL
What does the growth of a bar form lead to?
- Narrowing of the breaker zone
- Increased breaker intensity
Sediment transport patterns of bar initiation
- Convergence near breaker zone of onshore transport under shoaling and breaking waves with offshore transport in the undertow
Dimensionless fall velocity between 0-2
- Reflective Type beaches
- Low RTR = Reflective, cusps, steps, short profile length
- Intermediate RTR, 3-7: Low tide terrace plus rip, cusps, reflective beach face
- High RTR, 7-15: Low tide terrace, long beach profile, reflective high tide beach, dissipative low tide terrace
Dimensionless fall velocity between 2-5
- Intermediate type beaches
- Low RTR: Barred beach, steep beach face w/ deep trough and pronounced bar or subdued bar-morphology
- RTR 3-7: Low tide bar/rip, low tide transverse bar and rip morphology, steeper beach face, swash bar
- RTR 7-15: Ultra dissipative, flat and featureless, very long profile
Dimensionless fall velocity >5
- Dissipative type beaches
- Low RTR: Barred dissipative w/ multiple subdued bar-trough morphology
- RTR 3-7: Non-barred dissipative, flat and featureless
- RTR 7-15: Ultra-dissipative, flat and featureless w/ very long profile
