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Coastal Erosion And Its Control

Erosion is when wind,  water, and ice take sediments away.
Erosion on coasts by wind and water.
Water is major agent of erosion.
About 21% of all erosion in done by coastal erosion.

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Coastal Erosion And Its Control

  1. 1. AUTHOR: PARTHA DAS SHARMA, E.mail:, Website:
  2. 2. COASTAL EROSION 1. Coastal Processes. 2. Coastal Land forms 3. Impacts and Hazards on Coasts. 4. Prevention Methods used.
  3. 3. Coastal Erosion Erosion is when wind, water, and ice take sediments away. Erosion on coasts by wind and water. Water is major agent of erosion. About 21% of all erosion in done by coastal erosion. http://saferenvironment.wordpres 3
  4. 4. Coastal Processes Currents and Waves. Swash and Backwash of waves. Tides and Tidal Currents. Rip Currents. Long Shore drift. Hurricanes and Tsunami. Abrasion & Attrition. Corrosion (Salutation). http://saferenvironment.wordpres 4
  5. 5. Waves and Currents A wave is a disturbance that propagates through space and time. Current is a continuous flow of water in a particular direction. Both contains characteristics of Crest and Trough. http://saferenvironment.wordpres 5
  6. 6. Swash and Back wash Swash is the water that washes up on shore after an incoming wave has broken. Also called as constructive current. Backwash current is a seaward current that results from the receding swash. Also called destructive current. http://saferenvironment.wordpres 6
  7. 7. Swash and Back wash http://saferenvironment.wordpres 7
  8. 8. Tides and Tidal currents Tidal bulge combine with daily earth’s rotation creates broad system of waves. Cause by the gravitational action. Mainly because of moon and sun. Incoming tides and out going tides. Neap and Lunar tides. http://saferenvironment.wordpres 8
  9. 9. Rip Currents Fast, narrow surface currents. Flow seaward at nearly right angles to shore. Mainly in surfing zone. Move back to sea by narrow paths. http://saferenvironment.wordpres 9
  10. 10. Long Shore Drift The movement of sediments along a beach or shore by currents. Having a particular direction. Mainly cause by Long shore currents. Swash and Backwash are major Phenomena. http://saferenvironment.wordpres 10
  11. 11. Hurricane and Tsunami Hurricane A tropical cyclonic storm with winds having speed >120km/hour. Mostly hit in late summers and fall. Tsunami A short period disturbance create by submarine earth quake or volcanic vent. The waves more than 100feet, might possibly rise. http://saferenvironment.wordpres 11
  12. 12. Abrasion & Attrition(Corrasion) Abrasion. The waves pick up the sediment & hurl it against the cliffs (uses the sediment as ammunition). Attrition As the sediment is hurled against the cliff, bits are chipped off, the sediment gets smaller & rounder http://saferenvironment.wordpres 12
  13. 13. Corrosion (Salutation) Salt & other chemicals in sea water attack & dissolve the cliffs. The cliffs mainly of limestone and calcium rich are mainly effected. http://saferenvironment.wordpres 13
  14. 14. Coastal Land Forms. Headlands and Bay Mouth Bars. Barrier islands and Barrier Reef. Atolls and Reef Flats. Fore shore and Back shore. Berms and Spits. Cliffs, Crack or Inlet. Caves and Arches. Stack and Stump. Wave Cut Platform Tombolos http://saferenvironment.wordpres 14
  15. 15. Headlands and Bay mouth Bars. Headlands A headland is an area of land adjacent to water on three sides. Where the rock is hard a Headland is left outstanding. Bay mouth bars A shallow bar, extends partially or completely across the mouth of bay. Where there is softer rock erosion carves out a bay. http://saferenvironment.wordpres 15
  16. 16. Barrier Island and Barrier Reef Barrier Island Elongate ridges of sand and gravel parallel to coasts, forms at long shallow shelf. Separated from mainland by shallow lagoon. Barrier Reef Coral reef that parallel to shore. Separated by open water. http://saferenvironment.wordpres 16
  17. 17. Atolls and Reef Flats. Atoll A ring shaped coral reef, encloses a lagoon. Grows upward from submerged volcanic peak. Reef Flats A platform of coral fragments and sands. Exposed only in low tidal zone. http://saferenvironment.wordpres 17
  18. 18. Fore Shore and Back Shore. Fore shore is the shore between low and high tide lines. This area continuously attacked by currents and waves. Back shore is the inner portion of the shore that is land ward having gentle sloping. It is only attacked by waves during high tides and in severe storms. http://saferenvironment.wordpres 18
  19. 19. Berms and Spits Berms Horizontal portion of a beach whose edge abruptly slopes seaward. Located in Back shore zone. Spits A narrow strip of land, usually of sand. Whose one end attached with mainland and ends in water. http://saferenvironment.wordpres 19
  20. 20. Cliffs, Crack or inlet A cliff is a steep, often vertical, rock outcrop along a coast. The waves erode the rock through processes such as hydraulic action and corrosion. Wave attack picks out cracks, joints & weaknesses in the cliff. With time these weaknesses are widened, to form inlets or Goes http://saferenvironment.wordpres 20
  21. 21. Caves and Arches. The inlets with time further opened due to action of currents and waves form Caves. The hole broken through the rock makes an arch http://saferenvironment.wordpres 21
  22. 22. Stack and Stump. A pillar of rock surrounded by sea is left as a stack. Pressure is put on the arch roof until it collapses. Waves undercut the base of the stack until only a rock stump is left. Stump then disappears later on due to wave attacks http://saferenvironment.wordpres 22
  23. 23. Wave cut Platform The cliff above the wave cut notch eventually collapses leaving the cliff further back. Repeat this process & a wave cut platform is left at the cliff foot, indicating retreat http://saferenvironment.wordpres 23
  24. 24. Tombolos Derived from an Italian word means"long chain of rocks “. It is a deposition landform in which an island is attached to the mainland by a narrow piece of land such as a spit or bar. http://saferenvironment.wordpres 24
  25. 25. Impacts and Hazards on Coasts Plate Tectonic Impacts. Due to the movement and collision of Plates. Human made impacts. Due to Man made artificial structure and human activity. http://saferenvironment.wordpres 25
  26. 26. Plate Tectonic Impacts Divergent/Convergent plate boundaries possess steep continental shelves Passive Continental Margins- have broad continental shelves and have beaches with spit Island Arcs can protect coastlines Allows deltas to form http://saferenvironment.wordpres 26
  27. 27. Human Impacts on Coastline Retention walls, groins, and Revetments all cause large bulk deposition of sediment somewhere. Other areas lose beach sand Development destroys vital shoreline vegetation Water and petroleum pumping cause subsidence http://saferenvironment.wordpres 27
  28. 28. Hazards Related to Coasts Mass wasting. Danger to Urbanization. Danger to Marine life. Permanent Changes in Topography. http://saferenvironment.wordpres 28
  29. 29. Mass Wasting. 1. Include mainly land slide. Land slide causes the sediments to erode in a large bulk. Triggered due to hurricanes, Tsunamis. Results are heavy loss of property. 2. Process of Rock fall. When a hard cliff is under cut by waves the bulk of rocks fall under the influence of gravity. The Speed of fall might exceeds about 500km/hour. Cause structures to subside and heavy turbulence in water. Triggered coastal floods. 3. Toppling. Rotation of a mass of rock, debris, or earth outward from a steep slope face is called Toppling. Toppling also produce turbidity and might also destroy structures http://saferenvironment.wordpres 29
  30. 30. Danger to Urbanization Heavy loss of property taken place every year. Loss of life also taken place. Oil spillage during extreme storms may also cause various diseases. Sea water intrusions with drinking water bodies also a major hazard Different under ground structures might become exposed and become collapsed. The Most Effected urban countries of world is Holland and Japan. http://saferenvironment.wordpres 30
  31. 31. Danger to Marine life. The marine life specially the shelf marine life heavily suffer. Due to continuous erosion the shelf life heavily buried inside and become extinct, Oil spillage near shore destroy the coral reefs and other biodiversities. The production rate also disturbed as the eco system changes with coastal processes. Every year about 24-29% of all marine life near coast effected by various coastal factors. http://saferenvironment.wordpres 31
  32. 32. Permanent Changes in Topography The continuous erosion move the shelf further landward. The artificial constructed structure don’t control the rate of sediments. A large bulk of sediments erodes from one side and deposited at some other side, disturbing Isostacy. The artificial structures restrict the natural land forms. http://saferenvironment.wordpres 32
  33. 33. Prevention Methods Used. Structural Measures. Non-Structural Measures Bio Shield Methods http://saferenvironment.wordpres 33
  34. 34. Structural Measures. Sea walls. Groins. Jetties. Bulkheads Revetments. http://saferenvironment.wordpres 34
  35. 35. Sea walls In order to stop high tides http://saferenvironment.wordpres 35
  36. 36. Groins It is oriented perpendicular to shore http://saferenvironment.wordpres 36
  37. 37. Jetties On the both side of inlets http://saferenvironment.wordpres 37
  38. 38. Revetments Stop the erosion http://saferenvironment.wordpres 38
  39. 39. Bulk Heads They also used for steep slope stability http://saferenvironment.wordpres 39
  40. 40. Non Structural Measures Building sand dunes and growing vegetation around them. Artificial beach nourishment http://saferenvironment.wordpres 40
  41. 41. Coastal Dunes Vegetation, wind-flow and sand transportation are all inter-dependant in the coastal dune environment. Air movement and not water movement form the coastal dune, unlike most coastal features, and is therefore quite unique. The coastal dune is characterised by an interaction between sand transport by the wind and vegetation cover. Under both natural and human induced circumstances the dune can become unstable, and this can lead to coastal erosion. http://saferenvironment.wordpres 41
  42. 42. Bio Shields • Mangroves • Coral reefs • Sea grass • Sea weeds • Animal habitats • Marine parks • Marine sanctuaries http://saferenvironment.wordpres 42

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Erosion is when wind,  water, and ice take sediments away. Erosion on coasts by wind and water. Water is major agent of erosion. About 21% of all erosion in done by coastal erosion.


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