Coastal Dynamic Course from one of the top public universities in the world, ranked #2
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Course
CIE4305
Institution
Technische Universiteit Delft (TU Delft)
Coastal regions all over the globe experience environmental pressure both due to human interventions, exploitation and occupation and due to climate change impacts. This coastal engineering course focuses on education and research related to coastal systems, such as dune and barrier coasts, estuari...
Coastal Dynamics I (Technische Universiteit Delft)
, H1 Coastal morphodynamics = Study of coastal evolution Linear propagation: (Linear waves No current)
Morphology: underwater topography Morphodynamics: defined as the Dispersion relation: Wave frequency: = ∗ tanh ℎ = , = H5 Coastal Hydrodynamics
mutual adjustments and morphology of hydrodynamic processes involved Water waves are dispersive Phase velocity of longer waves is larger.
sediment transport. Equilibrium concept: Negative feedback: stabilization “ Group: Waves disappear at the front and reappear at back, c>cg
process causing the system to return to the (stable) equilibrium in case of Phase speed: speed of phase point (crest): = / = /
perturbations Positive feedback: destabilization process causing the system Limits: Shallow=non-dispersive, Deep=dispersive.
to move away from (unstable) equilibrium in case of perturbations. Shallow (depth depend): tanh ℎ ≈ ℎ → = ℎ; =
Deep (c depends on frequency): tanh ℎ ≈ 1 → = ; = =
H2 Large scale coastal variations
Tsunamis: Extreme long waves. (T=5-60 min, h/L<0.5, low energy loss)
Introduction: Plaatje sheet 6
st
1 order features: thousands of km’s (Broadcast features of the coast.) Group velocity: <c, except for very long waves: = , = +
!"#
∆
Controlled by continental shelf width, varying from 10m to 1500 km. =∆ = − , =∆ , = − , =∆ , =∆
nd rd
2 order: hundreds of km’s (outer banks of N. Carolina) 3 : few km’s. Transformation: Storm ( Direction)
Medeo-tide: Wind has more influence than tide (very shallow water). Area of generation, Combined, -long+intermediate, Long period waves
Ocean: where depth > 1km, Continental shelf: Shallow area, connected Generation of tide:
to continent Shelf width: Wide and flat: sediment accumulation, Tide: Sinusoidal semi-diurnal water level variation modified with:
Permit more rapid coastal progradation, Reduce wave energy to a large - A fortnightly spring- and neap-tide amplitude variation.
extent, Amplify tidal amplitude, higher potential storm surge elevations. - Daily inequality that varies with latitude and with monthly cycle.
Geographical variation of Coastal material: Attractional forces:
Coastal diversity: Nature of material. ) )
&' = ( ,* and &! = ( ,- plaatje Sheet 52
Continental sediments: Sand, Mud, Gravel&Rock. Plaatje sheet 10 +* +-
Coral Differential pull generates the tide.
.
Shell On earths near side: ∆&! = &! = 0.46 ∆&'
+
Rebound: Holland is lowering due to no ice on Scandinavia anymore. Equilibrium theory: immediate response of the oceans to tidal forces.
Supply of sand and fines: to coast largest from 40N-40S - No inertia
Higher mud content in tropics: Chemical weathering and… - Negligible friction and Coriolis plaatje Sheet 54
Biotic factors: Coral reefs, Mangrove swamps (small latitudes), - Entirely ocean covered with uniform depth
Salt marshes (larger latitudes), Dune vegetation. Solar day: Time for earth to return to same position to sun = 24 hrs.
Techtonic plate settling: Lunar day: 24hrs, 50 min. Moon takes 29,5 days to return (=L. month)
Continental drift: Continent cluster Continents moving away fr. eo. Principal lunar tide M2: amp = 0.24 m; -Solar tide S2=0.46*0.24=0.11m
Leading edge Trailing edge Spring tide: S&L reinforce each other. Neap tide: S&L cancel each other.
Rugged, cliffed coastline Far from plate boundaries Tidal propagation
o
Mountain ranges near coast Temperate climate Dynamic theory: (Only around 65 S an Equilibrium tide can exist, >=N)
Vulcanic ranges furder from coast Broad coastal plains, delta’s barri’s - Continents prevent tidal wave from covering circumference of earth.
Tectonic unstable Tectonically stable - Land masses move water masses along with them, instead of tide.
Narrow continental shelf; steep Wide shelf: Balance equations: Local storage = Net import + Local productions
Large waves Limited wave action, Depth restriction: Smaller h’s Amplitudes increase, velocity more.
Rapidly flowing, short streams Larger tidal amplitudes Coriolis effect: Diverts a moving to the right on NH, left at SH.
Relatively coarse sediment supply And storm surge heights. Coriolis force: Pseudo-force to make Newton’s Eq’s of motion valid.
Acceleration: &3 = 45 = 2 7 ∗ sin : ∗ 5, V=current velocity. Max: poles
Tectonic classification: Coastal character is influenced by proximity to
Forces: ;<,=>?">@"! = 2 ∗ sin : ∗ A = 4A, ;B,=>?">@"! = −4C, SH:sin : < 0
and plate boundary. Leading/collision/convergent; Trailing/passive.
Co phase: connect all places with same phase at same time.
Afro-trailing coast: opposite coast is also trailing (slow development of
Co range: connect all places with same tidal range. ” Run around A.Ps
coast, no extensive deltas and little river sediment supply)
Amphidromic points: zero-tidal range Co-phase lines radiate away.
Amero-trailing coast: Far away from plate boundary, stable, wide shelf,
“systems: Resonance influenced by size and shape of basin.
large supply of sand, temperate cimate, delta. Ria: drowned river valley.
Coastally trapped Kelvin Wave: Linearised equations of motion.
Increasing maturity: Neo Afro Amero (+sed deposit +widest shelf)
- Cross-shore M-balance is Geostrophic: p-gradient balances Fcoriolis
Marginal sea: bordering a sea enclosed between the landmass and isle.
- Alongshore “: inertia balances p-gradient, c in phase with h.
Sandy coasts: Dominate subtropics and lower mid-latitudes: Humidit
Tidal analysis and prediction
climates, passive margin coasts, more energetic waves+tidal environme.
Discrete and known frequencies!
Sea level changes: Worldwide rise, shapes coast at local level.
Determine amplitudes and phases
Quaternary climate variations: Inheritance from ice-ages, glaciers.
Careful with: Nodal factor fn, astronomical argument βn
Holocene: interglacial, sea-level rise. (from 10.000 years ago till now)
Tidal levels (low): LAT, MLW, MLWS, MLWN, MLLW.
Pleistocene: period of repeated glaciations sea level fall during glacial
Tidal ranges: MHW-MLW (normal), MHWS-MLWS (Spring),-Neap
Global/Eustatic changes: Amount+expansion water, volume+shape Ocs.
Klickers:
Local effects: Seismic activity, regional subsidence by fluid withdraw,
1. Wave height represents total energy content of irregular wave: Hrms
Regional effects: Isostatic: Glacio=(un)loading by ice, Hydro=-by water.
2. Propagation speed of tsunami wave train (L=500km, h=6km): 873 km/h
Bruun rule: Equilibrium shoreface response to sea-level rise.
3. Swell traveling 1100 km, T=8s, h>50m. Trave time: 50 hours
Balance between sea-level change and sediment supply.
4. The tide needs a day to travel shallow North Sea basin to the Dutch coast
Regression: seaward shift of the shoreline (water regresses).
time between full moon and spring tide is about 2 days.
Transgression: landward shift of shoreline: flooding
Progradation: sediment deposited, shoreline moves seaward.
Retrogradation: sediment deposited but shoreline moves landward. H4 Global wave and tidal environments
Emergence: land emerges out of water due to relative sea-level fall. Zonal wind systems:
Submergence: inland regions flooded due to relative sea-level rise. Uneven heating of the sun: equator more than poles:
Classification Result: Heat advection by ocean currents and winds.
Valentin: Coast advances (emerge/depot),-retreats (submerge/erosion) Colt air sinks at the poles, warm air rises at equator. Plaatje S7
Shepard: Primary= shaped by non-marine agency, Secondary= -marine. Pressure belts: (due to coriolis)
Dutch coast character: retreat/advance periods, terrestrial+marine shpe Moderate easterlies polar high
o
Basis: Material(soft/origin), tectonic controls(Inman), Valentin, Shepard. Strong+variable westerlies 60
Galloway: relative Moderate persistent trade winds Plaatje S10 30o
influence of : Plaatjes sheet 66 Calm doldrums 0o
Wave: High and low pressure systems
Regional effects: Seasonally reversing monsoon, cyclones, L+sea breezes
River: Global wave environments: + Shape ’n orientation of oceans ‘n coastlines.
Closely related to: Wave generating systems, wind ‘n cyclonic regimes
Tide: Wave classes: low: Hs<0.6; medium: 0.6<Hs<1.5m; high energy Hs>1.5m.
Boyd: Storm wave climate West coast swell wave climate
Prograding coast: Tidal flats, delta, strand plains. Most energetic wave environment Year round in SH, winter in NH
o o
Transgressive coast: “, estuary, Lagoons, barriers. Between 40 and 60 N and S Between 0 and 40o N and S
Ternary Shoreline diagram: Year round in SH, winter in NH Americas, Africa, Australia, NewZ
Prograding fluvial source Plaatje Locally generated by westerlies Origin:NH & SH storm wave belts
Fluvial power Embayed mix source Steep, shortcrested, irregular and “also trade winds for tropic swell
Marine source multi directional waves (sea). Arriving: NW in NH and SW in SH
Westerly to SW directions Typical wave heights 1-2 m
DW: H’s: 2-3m [90%], 5-6m [10%] Decreasing towards equator
H3 Ocean wind, waves and tide: Wave/tide power Periods ≈ 5 s, longer during storms Persistent and long waves T≈ 10s
Definitions: East coast swell climate: as west coast but more moderate.
Deep water: speed depends on frequency (dispersive) c = gT/2pi Global tidal environments:
Shallow water: speed depends on depth (non-dispersive) c = sqrt(gh) Tidal environments: Semi-diurnal, mixed (Tropics), diurnal (S-Pole)
Dispersive wave group: waves disappear at the frond and reappear at Form factor expresses tidal character: F=(K1+O1)/(M2+S2)
the back, and individual waves travel faster than the group wave front. Variations in “: Controlled by large scale coastal configurations.
Coriolis force: a pseudo-force to make Newton’s equations of motion Coastal impact:
valid in our non-inertial frame of reference. Storm wave climate Swell wave climate
Amphidromic points have a zero tidal range. Co-range lines (lines of =High, short waves, highly variable =Low long waves (relatively const)
constant tidal range) run around the amphidromic points, co-phase lines Wide+Flat, multiple bars, dunes… Break close to shore, S onshore
(connect all places with high water at same time) radiate away from
Dynamic coastal profile Narrow sany profile, steep.
amphidromic points.
Dimensionless fall velocity: Ω = Hb/(ws*T) to indicate beach profiles.
Introduction:
Dissipative beach: Ω>6; Reflective beach Ω<1. ws= Sediment fall velocity.
Wave classification: based on disturbing-, restoring force, wave period.
Wave dominated features Tide dominated features
Sea: locally generated wind waves, Swell: Generated far away.
Short term statistics: Dynamic sandy coastal profile with Tides smear beach morphology
Sea state, Spectral variance/density bars and dunes. Wide, low-gradient, muddy t.-flats
Beach slope depends on waves Salt marshes, mangroves, ridges
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