IMS W3 Coasts, waves & tides

Question 1

Types of coast dynamic landscapes

Answer 1

Natural induced: water, wind, vegetation
Human induced: zandmotor

Question 2

First classification of coasts

Answer 2

Primary coasts: determined by terrestrial processes (Terrestrial erosion and submergence/terrestrial deposition)
Secondary coasts: determined by present-day marine or biotic processes

Question 3

Primary coasts: Terrestrial erosion and submergence

Answer 3

 Fluvial erosion and drowned river valleys (ria coast/ Maine)
 Glacial erosion coasts (fjord)
 Drowned karst topography (Florida, Thailand)

Question 4

Primary coasts: Terrestrial deposition(4)

Answer 4

 Glacial deposition coasts: under the ice cap landforms formed creating a specific coastal types (Denmark)
 Aeolian deposits: induced by wind (Saudi Arabia)
 Deltaic deposits: bird foot delta created by rivers that drag sediments outwards (Mississippi)
 Landslide coasts (California)

Question 5

Secondary coasts (3)

Answer 5

o Wave erosion coast: wave straightened cliffs
o Marine deposition coast: barrier island, lagoon, salt marshes (most common type)
o Biotic coast: fully dominated by animals (coral reefs, sea grass meadows)

Question 6

Boundary conditions of coasts (1/1 + 1/4)

Answer 6

Factors from the land
o Geological setting (sediment type, resistance to erosion)
Factors from the sea
o Wave climate
o Tide and other sea level changes
o Ice effects
o Biological effects

Question 7

Storm waves and swells

Answer 7

Storm waves: dominated by wind (4/5/6 meters)
West coast swell/east coast swell: low energy waves unless there is a cyclone (1-1.5/15 meters) Created over a big region.

Question 8

Tide environments, old classification

Answer 8

<2m non tidal: non to micro tidal: wave dominated coast
2-4 mesotidal: drumstick barrier island. Beach is wave dominated and the inlet tidal dominated.
4-6 macro tidal: funnel chaped: Maine. Tidal dominated
> 6 mega tidal

Question 9

New classification wave/tide environment

Answer 9

Relative imprtance of wave and tidal energy. Looking at tidal prism.

Question 10

Coastal change

Answer 10

Bio-morpho dynamics: sediment will change due to biological cycles.
Geomorphologic: physical is dominating.
Bio-geomorphologic: mangroves, reefs
Ecological: dunes that create no real change

Question 11

Waves factors

Answer 11

Wind velocity
Wind duration
Fetch

Question 12

Vertical motion waves

Answer 12

Deep water: orbital paths: d/L = > 1/4
Intermediate water: ellipse: 1/4 > d/L > 1/20
Shallow water: no vertical motion: d/L < 1/20

Question 13

Storm waves Netherlands

Answer 13

Between 4-6 meters.
Wave period: 8-10 s.
From the North West high waves: long fetch.
From the South West low waves: UK is in the fetch.

Question 14

Dispersion relationship

Answer 14

Unique relationship between wave length, wave period and water depth.

Question 15

Wave breaking

Answer 15

Spilling: white foam
Plunging: surfer wave
Surf break: collapsing wave: water spills over itself.

Question 16

Subtidal bars

Answer 16

• 1 or 5 alongshore sand ridges below the low-tide line
• 10 – 100 km in the alongshore direction
• life time: up to 20 years
• alongshore variability: rips and crescentic shapes
  Very dynamic:
  – Cross-shore migration
  – Changes in alongshore variability

Question 17

Australian beach model Wright and Short

Answer 17

Dissipative beach
Intermediate beach
- Longshore bar and trough
- Rhythmic bar and beach
- Transverse bar and rip
- Low tide terrace
Reflective beach

Question 18

Storm response tidal bars

Answer 18

During: bar moves offshore due to undertow. 3D features are wiped out.
After: bar moves onshore due to mass transport. 3D features develop and grow.

Question 19

Different time periods tides

Answer 19

semidiurnal
mixed
diurnal

Question 20

Tide characteristics

Answer 20

Wavelength depend on tidal period.
Shallow water wave: wave length and period are very long compared to depth.
Moves faster in the ocean.
Standing wave

Question 21

tide generating force

Answer 21

Gravitational force - Centrifugal force
Only seen in fast water areas.

Question 22

Diurnal tides

Answer 22

Eath axis is titled which creates two bulges do to the centrifugal force of the moon. M2.

Question 23

Kelvin wave

Answer 23

Created by Coriolis force. Balances the force of the coastline. Not created by wind as coriolis force is not visible due to small lenght scales.

Question 24

Amphidromic points

Answer 24

Bulge where the tide moves around. A Kelvin wave also moves around the point. The tide and kelvin can cancel eachother out. There is no tide in the point.

Question 25

Tides and kelvin wave on shelf sea

Answer 25

• Largest amplitudes near the coast.
• A place with no tidal variations (amphidromic point)
• Tides that rotate around amphidromic point.
• This resembles observed tidal patterns in enclosed shelf seas

Question 26

Consequences tidal wave into estuaries

Answer 26

• Strong influence of morphology and shape of basin/estuary on tidal characteristics.
• In estuaries interaction of river and tides.
• Decrease or increase of tidal amplitude due to friction, resonance and funneling.
• Tidal waves become asymmetric and can thereby cause net sediment transport.

Question 27

Factors tide

Answer 27

Water level variations: tidal range
Flow velocities: tidal prism

Question 28

Tidal inlets

Answer 28

Created by tide dominated energy. All different inlets are seen as different tidal basins –> tidal divide. The basins are filled in motion.

Question 29

Different basins

Answer 29

Short basin <1/10 wavelength. Tidal range is constant. (standing wave)
Resonance: ~ 1/4 wavelength. Tidal range at end of basin larger than in inlet.
Tidal wave losses energy in basins as they are shallow.

Question 30

Different tidal inlets

Answer 30

Tide dominated
Mixed energy straight
Mixed energy offset
Wave dominated

Question 31

Relations tidal prism - basin

Answer 31

Channel volume is related to tidal prism by the power of 1.55.
Area of inlet cross section is related to tidal prism.
Volume of ebb tidal delta is related to tidal prism to the power of 1.23.

Question 32

Ebb tidal delta

Answer 32

Sediments are deposited in the ebb tidal delta as the flow expands out of the inlet can no longer hold the sediments anymore. The ebb tidal delta can be eroded by the tidal current parallel and littoral drift.