Civil Engineering along the coast
1 / 16

Civil Engineering along the coast -environmental problems and solutions - PowerPoint PPT Presentation

  • Uploaded on

Civil Engineering along the coast -environmental problems and solutions. Dr. M. C. Deo IIT Bombay. Contents Introduction - types of problems, damage Structural measures - dykes, sea walls, bulkheads, revetments, groins,

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Civil Engineering along the coast -environmental problems and solutions' - bernad

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Slide1 l.jpg

Civil Engineering along the coast

-environmental problems and solutions

Dr. M. C. Deo

IIT Bombay


Introduction - types of problems, damage

Structural measures - dykes, sea walls, bulkheads, revetments, groins,

storm surge barriers

Non-structural measures- sand dunes, beach nourishment,

bio-shields (mangroves, coral reefs)


Slide2 l.jpg


  • Indian coastline (~7500 km)

  • vulnerable to hazards

    normal wind, waves,

    tides, currents,

    sediment movement

    extreme cyclones,

    storm surges, (~6 / yr)

    tsunami, (1, 2/century)

    oil spills,…

  • Impact depends on: -Density of population, (25 %  within 50 km)

    -Design of structures and quality of construction,

  • -Environment (presence of mangrove forests,..)

Cyclones storm surges l.jpg
Cyclones & Storm surges

  • tropical cyclone a rotating wind

    (low pressure disturbance

    generally with heavy rainfall)

  • As cyclone approaches coastal area,

    strong on-shore winds create water current circulation,

    together with lowering of pressures

     rise of several meters in sea level

    (Storm surge)

     flooding large areas of the coast

Tsunami l.jpg

Primary : Earthquake

  • Cause

    Secondary : Landslides, volcanic activities

    Wave ht. @ shore : 20m or more

    Time of oscillation

    Tsunami: 30 to 60 min

    Wind generated gravity waves: 3 to 20 sec

    Tides: 12 or 24 hr

Warning system:

Occurrence of the tsunami-generating earthquake

can be recorded on seismographs

and communicated via satellites to the warning center,

where computer-based models calculate tsunami heights and travel times.

This could be verified by a series of wave rider buoys and accordingly

tsunami warning can be issued.

Such warning systems exist in Pacific countries including the U.S. and Canada

since 1964.

Slide5 l.jpg

  • Damage due to water coming from the sea:

    - Associated hydrostatic, hydrodynamic forces,

    - Impact of objects being carried by the attacking water mass,

    - High speed currents, overtopping,

    - Resulting flooding and current induced erosion.

Coastal erosion by breaking waves and associated currents l.jpg
Coastal Erosion - by breaking waves and associated currents

Oil Spills

caused by accidents involving

tankers, barges, pipelines,

storage facilities

can harm marine life, which in turn can harm human beings through food

Slide7 l.jpg

Structural measures for hazards reduction

  • Sea Dykes

  • Protect low-lying areas against flooding

  • Mound of sand and clay – sloping towards sea to reduce wave run up

  • Slope surface armored with grass, asphalt, stones, or concrete slabs

Shore protection manual, 1984, Coastal Engineering Manual, 2003

Slide8 l.jpg

Sea walls

Sloping faced (armored with concrete slabs

or armor units)

Parallel to shoreline

Vertical faced (concrete or stone filled)

Problem --

toe erosion

(use with


Slide9 l.jpg

Revetments -- protection from erosion

Bulkheads -- basically for slope stability

Slide10 l.jpg


- Fixed or adjustable

- High or low height

- Permeable or impermeable

Walls Perpendicular to shoreline; rubble mound or sheet piles

Updrift  accretion

Downdrift  erosion

 saw-tooth shoreline

Storm surge barriers A series of movable gates (sliding or rotating)

that prevent water intrusion in low lying areas

- open – normally; but closed – in storm surges

Slide11 l.jpg

Non-structural measures

--Building sand dunes and growing vegetation around them

--Artificial beach nourishment – removal of sand from one place and

and transportation to some other place

upstream where erosion feared

--Providing bio-shields

Bio shields l.jpg

  • Mangroves

  • Coral reefs

  • Sea grass

  • Sea weeds

  • Animal habitats

  • Marine parks

  • Marine sanctuaries

Mangroves l.jpg

  • Located in inter-tidal regions, can grow in saline water and in sheltered places like creeks and estuaries

  • Act as buffer against storm surges arrest erosion, trap sediments, harbor fish

  • But certain species are sensitive to excessive sedimentation, stagnation, oil spills

In recent Gujarat and Orissa cyclones,

presence of mangrove buffers  less destruction

(Source: protect/images/mangroves.jpg)

Coral reefs natural barriers against erosion and storm surge l.jpg
Coral Reefs-natural barriers against erosion and storm surge



  • corals  slow growing colonies of animals

    - growth rate = 1, 10 cm / yr.

    - occur in shallow tropical areas

    - sea water should be clean, clear and warm - provide habitat for a large variety of animals and plants

Slide15 l.jpg

destruction - outbreak of reef-destroying animals,


depletion of essential symbiotants

chemical pollution,

mechanical damage,

nutrient or sediment loading

  • necessary to quantify the

    protection the bio-shields provide

    and determine limits beyond which

    they are not so effective

Oil spill control l.jpg
Oil spill control

  • Mechanical Containment

    • Booms and barriers >

    • Skimmers

    • Sorbents (oil collecting sponges)

  • Chemical and Biological dispersants

    -- disintegrate oil

    -- Used in conjunction with mechanical means