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Understanding coastal processesand problems to produce successful     management solutions. A case study of Dawlish Warren...
Shallow Water Waves :• Waves change as they move into shallow water• motion of water molecules changes                    ...
Moving into shallow water the sea floor starts to interfereAs water shallows wavelength and wave velocity decrease• wave h...
The wave breaks :• water runs up the beach until stopped by gravity – the swash• water then flows back down the beach due ...
Beaches : Shore Normal Morphology :   • beach – loose pile of sand and gravel   • survives in high energy environment…….wa...
How will this effect sediment movement?   Beach Shape?        – these are constructive waves        – give us summer profi...
• net seaward movement of sediment        – destructive waves        – winter profile        – wider flatter beach   Beach...
Longshore currents :   • waves may approach the coast at angle   • usually <100 due to refraction   • swash approaches at ...
Longshore Drift :   • wave process leads to characteristics landforms   • landforms become detached from the coast   Spits...
The spit then extends across the indentation in the coast   • can extend right across bay bar        – if an estuary the h...
Profile 1                                                                                        Profile 2                ...
Ga Dawlish 2012
Ga Dawlish 2012
Ga Dawlish 2012
Ga Dawlish 2012
Ga Dawlish 2012
Ga Dawlish 2012
Ga Dawlish 2012
Ga Dawlish 2012
Ga Dawlish 2012
Ga Dawlish 2012
Ga Dawlish 2012
Ga Dawlish 2012
Ga Dawlish 2012
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Ga Dawlish 2012

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Ga Dawlish 2012

  1. 1. Understanding coastal processesand problems to produce successful management solutions. A case study of Dawlish Warren. Dr. Chris Spencer University of the West of England, Bristol
  2. 2. Shallow Water Waves :• Waves change as they move into shallow water• motion of water molecules changes http://www.oceanpix.co.uk/wave-simulator.htm
  3. 3. Moving into shallow water the sea floor starts to interfereAs water shallows wavelength and wave velocity decrease• wave height increases• wave steepens• crest becomes narrower and steeper, can’t continue• the wave breaksThe point at which this happens variesHow does this vary on steep / shallow beaches?
  4. 4. The wave breaks :• water runs up the beach until stopped by gravity – the swash• water then flows back down the beach due to gravity – the backwash
  5. 5. Beaches : Shore Normal Morphology : • beach – loose pile of sand and gravel • survives in high energy environment…….walls get destroyed?? How do beaches survive? • beaches are mobile • adapt shape to conditions • walls are fixed Low energy conditions (summer) – beach relatively steep - reflective – waves break onto the beach, relatively well spaced out – backwash returns before the next swash – swash not slowedLecture 3 : Dr Chris Spencer
  6. 6. How will this effect sediment movement? Beach Shape? – these are constructive waves – give us summer profiles – berms at the back of the beach Under high energy conditions (winter) – beach slope is more gentle – absorb / dissipate – spilling breakers, breaking over beach – waves arrive in rapid succession – backwash interferes with the next swash – reduced ability to move seidmentLecture 3 : Dr Chris Spencer
  7. 7. • net seaward movement of sediment – destructive waves – winter profile – wider flatter beach Beach shape is also influenced by particle size • this is due to the variable permeability • coarse beaches are more permeable • swash dominates, backwash returns through the beach • net sediment movement up the beach – increases gradientLecture 3 : Dr Chris Spencer
  8. 8. Longshore currents : • waves may approach the coast at angle • usually <100 due to refraction • swash approaches at an angle • backwash returns with gravityDr Chris Spencer : Lecture 3
  9. 9. Longshore Drift : • wave process leads to characteristics landforms • landforms become detached from the coast Spits – narrow, elongate beaches – detached from the coast • longshore drift transports sediment along the coast • where the coast is ‘indented’ some of this sediment is deposited • the longshore drift can now extend furtherLecture 3 : Dr Chris Spencer
  10. 10. The spit then extends across the indentation in the coast • can extend right across bay bar – if an estuary the high discharge will keep this open • spits have a characteristic hook shape at the end, a recurve • often a whole series of recurves visible Example : Dawlish Warren 2 theories – waves approach and slow in the shallows – curve around the spit – angle of the wave varies – builds up a recurveLecture 3 : Dr Chris Spencer
  11. 11. Profile 1 Profile 2 9 9 8 8Height (m) 7 7 Pre-storm Height (m) 6 Post-storm 6 5 5 4 0 20 40 60 80 4 0 20 40 60 80 100 Distance along transect (m) Distance along transect (m) Profile 3 Profile 4 9 8 9 7 8 7 6Height (m) Height (m) Pre-storm 6 5 Post-storm 5 4 4 3 0 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140 Distance along transect (m) Distance along transect (m)

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