Coastal Erosion

COASTAL EROSION. BY JAWAD BASHIR(THUNDER)

GROUP MEMBERS

3. 4. 5.

Enam-ul-haq malik. Haroon Khan. Jawad Bashir.

COASTAL EROSION 1.

Coastal Processes.

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Coastal Land forms

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Impacts and Hazards on Coasts.

10.

Prevention Methods used.

13.

Coastal Erosion in Pakistan.

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.

Coastal Processes •

Currents and Waves.

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Swash and Backwash of waves.

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Tides and Tidal Currents.

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Rip Currents.

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Long Shore drift.

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Hurricanes and Tsunami.

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Abrasion & Attrition.

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Corrosion (Salutation).

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.

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.

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Longsho re Drift

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Longsho re Drift

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Tides and Tidal currents. •

Tidal bulge combine with daily earth’s rotation creates broad system of waves.

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Cause by the gravitational action.

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Mainly because of moon and sun.

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Incoming tides and out going tides.

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Neap and Lunar tides.

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.

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.

Hurricane and Tsunami. • A tropical cyclonic storm with winds having velocity>120km/hour. • Mostly hit in late summers and fall. • A short period disturbance create by submarine earth quake or volcanic vent. • The waves more than 100feet, might possibly rise.

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

Corrosion (Salutation) • Salt & other chemicals in sea water attack & dissolve the cliffs. • The cliffs mainly of limestone and calcium rich are mainly effected.

Coastal Land Forms. • • • • • • • • • •

Head lands 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

Headlands and Bay mouth Bars. •

A headland is an area of land adjacent to water on three sides. • Where the rock is hard a Headland is left outstanding. •

A shallow bar, extends partially or completely across the mouth of bay. • Where there is softer rock erosion carves out a bay.

Barrier Island and Barrier Reef. • Elongate ridges of sand and gravel parallel to coasts, forms at long shallow shelf. • Separated from mainland by shallow lagoon.

• Coral reef that parallel to shore. • Separated by open water.

Atolls and Reef Flats. • A ring shaped coral reef, encloses a lagoon. • Grows upward from submerged volcanic peak. • A platform of coral fragments and sands. • Exposed only in low tidal zone.

Fore Shore and Back Shore. • The shore between low and high tide lines. • This area continuously attacked by currents and waves. • The inner portion of the shore that is land ward having gentle sloping. • Only attacked by waves during high tides and in severe storms.

Berms and Spits. • Horizontal portion of a beach whose edge abruptly slopes seaward. • Located in Back shore zone. • A narrow strip of land, usually of sand. • Whose one end attached with mainland and ends in water.

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 corrasion.

• Wave attack picks out cracks, joints & weaknesses in the cliff. • With time these weaknesses are widened, to form inlets or Goes

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

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

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

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.

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.

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

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

Hazards Related to Coasts. • Mass wasting. • Danger to Urbanization. • Danger to Marine life. • Permanent Changes in Topography.

Mass Wasting. • • • • •

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. Average 8,774,406 billion dollars loss taken place.

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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.

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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

Danger to Urbanization •

Heavy loss of property taken place every year.

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Loss of life also taken place.

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Oil spillage during extreme storms may also cause various diseases.

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Sea water intrusions with drinking water bodies also a major hazard

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Different under ground structures might become exposed and become collapsed.

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The Most Effected urban countries of world is Holland and Japan.

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.

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.

Prevention Methods Used. • Structural Measures.

• Non-Structural Measures

• Bio Shield Methods

Structural Measures. • • • • •

Sea walls. Groins. Jetties. Bulkheads Revetments.

Sea walls in order to stop high tides

Groins It is oriented perpendicular to shore

Jetties on the both side of inlets.

Revetments. Stop the erosion.

Bulk Heads. They also used for steep slope stability.

Non Structural Measures. • Building sand dunes and growing vegetation around them. • Artificial beach nourishment

Bio Shields • • • • • • •

Mangroves Coral reefs Sea grass Sea weeds Animal habitats Marine parks Marine sanctuaries

Coastal Erosion in Pakistan. • The Pakistan’s coastline with the Arabian Sea stretches to over 990 km. • The Balouchistan coast is active whereas the Sindh coast, Indus deltaic area, and offshore Indus basin are passive. • Balouchistan coast mainly contains Gawadar coastal area. • Sindh coast can be further divided into two parts the Indus deltaic coast and the Karachi coast

Ecosystem found. • Mangrove forests in the Indus delta, which are a rich source of nutrients for a variety of marine species. • Avicenna marina being the most dominant. • Coral reefs and sea weeds also the main part of eco system. • Various types of birds, fishes and mammals also live in these areas.

Coast of Balouchistan • The coast of Balouchistan is about 400450 km. • The Makran coast consist mainly of Clastic sediments. • The Gawadar coast is rocky and compacted coast.

Makran Coast • Makran coast is not an well urbanized area. • On the west (Makran) coastal erosion already threatens coastal property, coastal agriculture land and habitats. • The Barrier island, bay mouth bars and Tombolos are main land forms. • Two major barrier islands of about 2-3 km are here.

Gawadar coast. • Gawadar coast is a rocky type of coast • Coastal erosion to some degree is only noticeable. • Rock fall often seen here. • Stack, stump, inlets ,head lands and wave cut platform is noticeable features here. • Coral reefs specially sea weeds are found here.

Indus Deltaic coast. • It is urbanized area. • Carrying most of the eroded alluvial soils and clay. • Coastal erosion on a massive scale is seen here, Land sliding is a major coastal hazard. • Oil spillage is often subjected to that area. • The land forms seen here are Deltas, bays, Tombolos and Berms. • Mangroves also the part of Eco system.

Karachi Coast • • • • • •

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Karachi coastal area is about 60km in length. Mainly consist of detrietal particles and sand. Heavily urbanized area. The Main hazard is coastal pollution by various means i.e. oil spillage is common. The phenomena of land subsidence is also present Mangroves are present in large number but there production become decrease with time. The main land forms are Bays, spits and barrier islands.

Prevention Methods Used in Balouchistan coast. • The government is not giving interest in Balouchistan coastal areas. • The only method used in Balouchistan (Makran) is the bulkhead method. • In Gawadar the national disaster control frame authorities will use sea walls in order to stop massive cliff erosions.

Prevention Methods used in Sindh coast. • Government is focusing specially on Karachi coast due to urbanization. • Retention walls are build at various places. • Bulkheads and artificial beach nourishment is common used methods here. • The marine geologists also working on method to increase mangroves production. • In Indus coastal area the Groin and jetties protection method is used to lessened the effects of coastal erosion.

The End. Any Questions.