Earth Resources and Engineering (21CV34)

MODULE 1
Introduction, scope of earth science in Engineering, Geohazards and disasters, Mitigation and
management
Earth Science (Geology)
This is the science that deals with the study of earth.
Branches of geology Related to civil engineering
1. Seismology
The science dealing with the study of earthquakes in all their aspects is called Seismology.
2. Hydrology
It is the science that deals with the properties, distribution, and circulation of naturally
occurring water on and under the earth’s surface and in the atmosphere.
3. Mining Geology
This branch of geology is concerned with the study of the application of geology to mining
engineering.
4. Engineering Geology
It includes the study of the application of knowledge of geology in the field of civil engineering
for the execution of safe, stable, and economic construction like dams, bridges, and tunnels.
5. Remote sensing
It deals with the interpretation of geological features such as landforms, structural features,
land use patterns, etc., with the help of aerial photographs and Landsat imagery for better and
fast management of geological resources and disaster management.
6. Environmental Geology
It deals with the environmental awareness, geological hazards, better management of natural
resources and waste disposal, etc.

Scope of Earth Science in Civil Engineering

1. Geology provides a systematic study of the structure and properties of construction materials
and their occurrence.
2. The selection of a site is important from the viewpoint of stability of foundation and
availability of construction materials. Geology provides knowledge about the site used in the
construction of buildings, dams, tunnels, tanks, reservoirs, highways and bridges.
3. Geology helps to identify area susceptible to failures due to geological hazards such as
earthquake, landslides, weathering effects, etc.
4. The knowledge about the nature of the rocks is very necessary for tunneling, constructing
roads and in determining the stability of cuts and slopes.
5. The foundation problems of dams, bridges and buildings are directly related to the geology of
the area where they are to be built.
6. The knowledge of groundwater is necessary for connection with excavation works, water
supply, irrigation and many other purposes. Hydrological maps provide information about the
distribution of surface water channels and the groundwater depth.
7. Geological maps help in planning civil engineering projects. It provides information about the
structural deposition of rock types in the proposed area.
8. Geology helps in determining the earthquake-prone areas. If any geological features like faults,
folds, etc. are found, they have to be suitably treated to increase the stability of the structure.
9. The knowledge of erosion, transportation and deposition (ETD) by surface water helps soil

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conservation, river control, coastal and harbor works.

10. A geological survey of a site before starting a project will reduce the overall cost.

INTERNAL STRUCTURE OF EARTH

Our Earth is a cosmic body. It is one of the nine members of the Solar system of which Sun is
the central star. The nine planets constituting the Solar system has been named as Mercury,
Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. In its shape, The Earth is
commonly described as a spheroid; it has an equatorial diameter of 12,757.776km and a polar
diameter of 12,713.824km and thus has an equatorial bulge.
At present the Earth is the only planet believed to be sustaining life other planets have shown
no signs of life on them. For systematic scientific investigations, the earth is commonly
differentiated into three parts; they are atmosphere, lithosphere and hydrosphere.

Based on the seismic Investigations, the earth can be divided into four major layers
1. Crust
2. Mantle
3. Outer core

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4. Inner core

Crust
The outer super special layer of earth is called the Crust. It extends down to 30 to 40km
beneath continents and 10km beneath Ocean basins at the bottom of the crust, The velocity of
earthquake waves increases abruptly as they enter into a denser layer called Mantle.
Mantle
At the base of the crust materials of the earth become greatly different in many properties
from those overlying them in the crust. The mantle is located beneath the earth crust and has a
thickness of about 2900km. It has been divided into 2 layers.
1. Upper mantle
2. Lower mantle
The boundary between these is at about 700km depth. In the lower mantle the density of
material increases rapidly. The upper mantle contains a most important zone called
Asthenosphere. It is located at depths between 50 to 100km.The outer solid portion of the
earth existing above the Asthenosphere is called lithosphere.
The lithosphere includes part of the upper mantle and the Crust.
Core
The boundary between the mantle and core is at a depth of about 2900km.
Inner core
Earth’s inner core is the innermost geological layer of the earth. It is primarily a solid ball with a
radius of about 1220km.
Outer core
Earths outer core is a fluid layer about 2400km thick and composed of mostly iron and nickel
that lies above Earth’s solid inner core and below its mantle.

Plate Tectonics
 Plate tectonics is the theory that Earth’s outer shell is divided into several plates that
glide over the mantle, the rocky inner layer above the core. The plates act like a hard
and rigid shell compared to Earth’s mantle. This strong outer layer is called
the lithosphere.
 The earth’s lithosphere is composed of seven or eight major plates and many minor
plates. The lithosphere is a rigid outermost shell of earth and is broken up into tectonic
plates. When these plates meet, their relative motion determines the type of boundary
like convergent, divergent, or transform.

 Volcanic activity, earthquakes, mountain-building, and oceanic trench formation occur

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along these plate boundaries. The relative movement of the plates typically ranges from
zero to 100 mm annually.
Causes of Plate Tectonics:
• Plate tectonics affects humans in several important ways.
• It causes earthquakes
• It causes volcanism
• It causes mountain-building

Types Of Plate Boundaries

(a) Divergent boundaries: where plates separate and move in opposite directions, allowing new
lithosphere to form from upwelling magma. This either occurs at mid-ocean ridges (the so-
called seafloor spreading) or at rifted continental margins.
(b) Convergent boundaries: where plates move towards each other. One plate either sinks
beneath the other along a subduction zone or plates collide because neither can be sub ducted.
(c) Transform fault boundaries: where plates move horizontally past each other.

Types of Earthquakes
Tectonic earthquakes: The most common form of earthquake, is caused by the movement of
loose fragmented pieces of land on the earth’s crust known as tectonic plates.
Volcanic earthquake: The less prevalent compared to the tectonic variety, these earthquakes

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happen before or after the eruption of a volcano. It is caused when magma leaving the volcano
is filled by rocks being pushed to the surface.
Collapse earthquake: This earthquake occurs in underground mines. The main cause is the
pressure generated within the rocks.
Explosion earthquakes: The occurrence of this type of earthquake is artificial. High-density
explosion such as nuclear explosions is the primary cause.

Causes of earthquakes:
Earthquake originates for various reasons and the causes may be grouped as follows:
a) Surface causes
b) Volcanic causes
c) Tectonic causes
a) Surface causes:
1. Large scale rock falls on lose and weak grounds/landsides
2. Dashing of sea .waves against weak coastal zones
3. Huge waterfalls on structurally displaced weak ground
4. Nuclear testing
5. Use of explosives in civil engineering, mining or other development works
6. Movement of heavily loaded trucks on soft and weak grounds
7. Fast moving trains/bullet trains
8. Storage of water reservoirs

b) Volcanic causes:
A violent volcanic eruption causes localized earthquakes, often earthquakes and
volcanoes areassociated both in space and time.

c) Tectonic causes:
The main cause of earthquake is a disturbance of structural features, where by sutures are
displaced in the crustal layers of the earth due to movements of the earth. The tremors
thus produced are called tectonic earthquakes. Most of the disastrous earthquakes have
taken place near major fault zones. Tectonic earthquake result due to sudden yielding to
the strain produced on the rocks by accumulated stresses.

Body Waves
Earthquake waves are of two types — body waves and surface waves.
P- Waves

 P-waves are also known as the Primary waves. They are the first waves to arrive at the
surface.
 The characteristics of P-waves are like sound waves. They travel through all three
mediums- solid, liquid, and gas.
 These waves tend to vibrate parallel to the direction of wave propagation. This causes
density differences in the material through which they travel.

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 These waves are responsible for elongating and squeezing material.

S- Waves

 S- Waves arrive sometime after the happening of the Earthquake and they are called
secondary waves.
 A significant characteristic of these S-waves is that they travel only through a solid
medium.
 The direction of vibration of this S-wave is perpendicular to the direction of wave
propagation, thereby creating crests and troughs in the material of their transmission.

Isoseismal lines
Whenever an earthquake takes place, the intensity which is maximum at the epicenter,
decreases outwards, the decreases in intensity is inversely proportional to square of the
distance from the Centre of disturbance. In an earthquake hit area, places of same intensity can
be marked. A line joining points of same intensity is called isoseismal line.

An Isoseismal (line) is a contour or line on a map connecting points of equal intensity relating
to a specific earthquake and confining the area within which the intensity is the same.

Seismic Zonation map

The Geological Survey of India (G. S. I.) first published the seismic zoning map of the country in
the year 1935. With numerous modifications made afterwards, this map was initially based on
the amount of damage suffered by the different regions of India because of earthquakes. Color
coded in different shades of the color red, this map shows the four distinct seismic zones of
India. Following are the varied seismic zones of the nation, which are prominently shown in the
map:

 Zone - II: This is said to be the least active seismic zone.

 Zone - III: It is included in the moderate seismic zone.
 Zone - IV: This is considered to be the high seismic zone.
 Zone - V: It is the highest seismic zone.

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Importance of India's Seismic Zoning Map

 This kind of map is mainly used by the Department of Disaster Management of the
different state governments in the country.
 This map helps them in planning for a natural disaster like earthquake. An Indian seismic
zoning map assists one in identifying the lowest, moderate as well as highest hazardous
or earthquake prone areas in India.
 Even such maps are looked into before constructing any high rise building so as to
check the level of seismology in any particular area. This in turn results in saving life in
the long run.

Earthquake resistant structures

Besides introduction of additional safety factors, some general precautions have to be
followed tominimize the danger of collapse or failure of a building during a shock. They are
summarized below:

(a) Foundations:

1. Structures built on loose soil or sediments or weak rocks will have to withstand greater
shock than those founded on solid bed rock. Naturally, it would be desirable that
foundations of costly structures are carried down to rest upon solid bed rock. Damage
to structures on soils may be due to settlement that follows compaction of the soil
particles due to seismic vibrations. Rocks, which are already sufficiently compacted
because of their mode of formation, will not normally suffer from such an effect and
hence offer better safety.
2. Foundations for concrete and masonry buildings should be excavated to the same
level throughout the building.

(b) The body:

1. The walls should be as light as possible, made up of either wood or light weight
concrete. Stronger and resistant walls should be designed using only reinforced
concrete.
2. Continuity of the cross walls should be maintained as for as possible and in such a way
that different parts of the building behaves as integrals of the same structure and not
randomly

(c) The roof:

1. Flat, R.C.C roofs give to the buildings greater resistance against tremors.
2. The roof should be so designed, even with the above material that it gives rise to no
lateral stresses during vibrations. For this very reason use of tiles, sheets, slates have
to be avoided which will slip at least lateral stresses.

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3. Projections above the roofs, such as chimneys etc., should be avoided.

(d) General:

1. All the parts of the same building should be firmly tied together, so that the entire
structure acts as a unit, simple or complex, during a shock and not as a multitude of
units placed close to each other irregularly.
2. Uniform height should be given to the building

3. Architectural features like, parapets, cantilevers, domes and arches etc., should be
avoided as far as possible.
4. Fault zones should be avoided, especially in case of dam construction.

Landslides and their control

Landslide is a slow or sudden downhill movement of slope forming rock and soil material
under the force of gravity. Landslides or slope failures are natural Erosional process. They
occur in hillsides valley slopes, seacoasts, riverbanks and bends, on the slopes of volcanic
cones and in earthquake prone areas. They also occur underneath as on lake or sea floor. Man
in his urban and regional development activities also trigger landslides during excavations,
fills quarries, cuttings of roads, railway and canals etc. Landslides as natural erosional
process not only modify the existing topography and landscape, they also cause immense
damages tomanmade structures and heavy loss of life.

Types of landslides
Landslides are of many types and are broadly classified according to their characteristic
parameters like, the presence or absence of a definite slip plane, materials involved and their
water content and the kind and rate of movement. The types include:

SLIDES: Although many types of mass movements are included in the general term
"landslide," the more restrictive use of the term refers only to mass movements, where there
is a distinct zone of weakness that separates the slide material from more stable underlying
material. The two major types of slides are rotational slides and translational slides.
Rotational slide: This is a slide in which the surface of rupture is curved concavely upward
and the slide movement is roughly rotational about an axis that is parallel to the ground
surface and transverse across the slide (fig. A). Translational slide: In this type of slide, the
landslide mass moves along a roughly planar surface with little rotation or backward tilting
(fig. B). A block slide is a translational slide in which the moving mass consists of a single unit
or a few closely related units that move downslope as a relatively coherent mass (fig. C).

FALL: Falls are abrupt movements of masses of geologic materials, such as rocks and boulders

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that become detached from steep slopes or cliffs (fig. D). Separation occurs along
discontinuities such as fractures, joints, and bedding planes, and movement occurs by free-
fall, bouncing, and rolling. Falls are strongly influenced by gravity, mechanical weathering, and
the presence of interstitial water.
TOPPLES: Toppling failures are distinguished by the forward rotation of a unit or units about
some pivotal point, below or low in the unit, under the actions of gravity and forces exerted
by adjacent units or by fluids in cracks (fig. E).
FLOWS: There are five basic categories of flows that differ from one another in
fundamental ways.
a. Debris flow: A debris flow is a form of rapid mass movement in which a combination of
loose soil, rock, organic matter, air, and water mobilize as a slurry that flows downslope (fig.
F). Debris flows include <50% fines. Debris flows are commonly caused by intense surface-
water flow, due to heavy precipitation or rapid snowmelt that erodes and mobilizes loose soil
or rock on steep slopes. Debris flows also commonly mobilize from other types of landslides
that occur on steep slopes, are nearly saturated, and consist of a large proportionof silt- and
sand-sized material. Debris-flow source areas are often associated with steep gullies, and
debris- flow deposits are usually indicated by the presence of debris fans at the mouths of
gullies. Fires that denude slopes of vegetation intensify the susceptibility of slopes to debris
flows.
b. Debris avalanche: This is a variety of very rapid to extremely rapid debris
flow (fig.G).
c. Earthflow: Earthflows have a characteristic "hourglass" shape (fig. H). The slope material
liquefies and runsout, forming a bowl or depression at the head. The flow itself is elongate
and usually occurs in fine-grained materials or clay-bearing rocks on moderate slopes and
under saturated conditions. However, dry flows of granular material are also possible.
d. Mudflow: A mudflow is an earthflow consisting of material that is wet enough to flow
rapidly and that contains at least 50 percent sand-, silt-, and clay-sized particles. In some
instances, for example in many newspaper reports, mudflows and debris flows are commonly
referred to as "mudslides."
e. Creep: Creep is the imperceptibly slow, steady, downward movement of slope-forming soil
or rock.Movement is caused by shear stress sufficient to produce permanent deformation,
but too small to produce shear failure. There are generally three types of creep: (1) seasonal,
where movement is within the depth ofsoil affected by seasonal changes in soil moisture
and soil temperature; (2) continuous, where shear stress continuously exceeds the strength
of the material; and (3) progressive, where slopes are reaching the point of failure as other
types of mass movements. Creep is indicated by curved tree trunks, bent fences or retaining
walls, tilted poles or fences, and small soil ripples or ridges (fig. I).

Lateral spreads:
Lateral spreads are distinctive because they usually occur on very gentle slopes or flat terrain
(fig. J). The dominant mode of movement is lateral extension accompanied by shear or tensile

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fractures. The failure is caused by liquefaction, the process whereby saturated, loose,
cohesion less sediments (usually sands and silts) are transformed from a solid into a liquefied
state. Failure is usually triggered by rapidground motion, such as that experienced during an
earthquake, but can also be artificially induced. When coherent material, either bedrock or
soil, rests on materials that liquefy, the upper units may undergo fracturing and extension
and May then subside, translate, rotate, disintegrate, or liquefy and flow. Lateral spreading in
fine-grained materials on shallow slopes is usually progressive. The failure starts suddenly
in a small area and spreads rapidly. Often the initial failure is a slump, but in some materials
movement occurs for no apparent reason. Combination of two or more of the above types is
known as a complex landslide.

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Control of Landslides
Many methods for controlling the slides are available and choice of many methods
will depend of factors like nature of slide, the underlying cause for it, the nature
and amount of material involved and the economical consideration, of such
method most important are.
1) Providing adequate drainage

2) Construction of retaining walls

3) Stabilizing the slopes

1. Providing adequate drainage: - It involves the removal of moisture form within

the rocks as well as preventing any further moisture to approach the material
to sliding. This may be achieved either by surface drainage or by subsurface
drainage; construction of interpretation ditches, waterways, trenches and
drainage tunnels may become necessary. Grouting the joints and other
fractures may also prove helpful.
2. Retaining structure: - Al such devices like construction of retaining wall etc. are
aimed at stopping the moving mass by force and their success is always
doubtful. Construction of retaining wall requires an accurate assessment of the
forces, which the wall has to withstand. Retaining walls may prove
exceptionally, successful where,
a. The ground is neither too fine nor too plastic

b. The sliding mass is likely to remain dry

c. The movement is of shallow nature

3. Slope treatment: - When the material is soil and situation is a slope the failure
is attributed to a loss of stability. In such cases the treatment involves stability
for the particular type of soil and slope and if such computation indicate that a
given slope of soil will not be stable then the solution lies in either,
a. Flattening the slope

b. Decreasing the load

c. Increasing the shearing resistant of the soil by decreasing its water

content with help of drainsand evaporation
d. A forestation that is growth of vegetation cover with intricate and
interwoven root system hasalso been found useful in stabilizing the
barren slopes.

Tsunami and their control

Tsunami is a Japanese word, which means, ‘harbor wave’. These are the large waves
that are generated when the sea floor is deformed by seismic activity, vertically
displacing the overlying water in the oceans.

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Characteristics of Tsunami

 Tsunami wave heights range from 1 to 524m.

 Wave lengths range from 500 to 800km.
 Wave periods vary between 100 and 2000s
 Tsunamis with long periods of 15 to 100m and with travel speed of 828 km/h are common in
PacificOcean
 Indian Ocean Tsunami (2004) waves travelled up to 800 km/h in open ocean

Causes of Tsunami

 Earthquake: Tsunamis are caused by sudden movements of the earth that happens under the
sea. Often the most destructive Tsunamis are caused by earthquakes but causes can also include
volcanic eruptions, landslides or even a comet hitting the sea.

 Landslides: cause tsunamis when the debris falls into the water. This has the same effect of
dropping a large stone into a pool - big ripples are created. But when this happens in the sea
and it is thousands of tonnes of rock and earth falling into the sea a very large ripple, more like
a tidal wave is created. This travels across the sea until it comes into contact with land and a
tsunami is formed.
 Volcanoes: cause tsunamis when there is an eruption. The volcano can either be on land or
under the sea, in which case it is known as a submarine volcano. If the volcanic eruption happens
on land, the tsunami is causedby debris and lava from the volcano flowing into the sea, which
once again causes a bug ripple.
If the eruption happens under water, the enormous power of the eruption sends shudders
through the earth and disrupts the water. The water in the sea then breaks into waves which
travel across the ocean until they come into contact with a coast. Here, a tsunami is formed.

Mitigation Measures
1. Effective Planning

2. The building of walls was done by Japan.

3. Planting trees as done in Tamil Nadu by a village

4. Proper relief and rehabilitation preparedness

5. Awareness among the masses

Volcanic Eruption
A volcano is a land-form, a mountain, where molten rocks erupt through the surface of the
planet. The volcano mountain opens downwards to a pool of molten rocks below the
surface of the earth.

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When the pressure builds up in the earth’s crust, eruptions occur. Gasses and rock shoot up
through the opening and spill over or fill the air with lava fragments. The volcano eruption
can cause lateral blasts, hot ash and lava flow, mudslides, and more.

Types of Volcanic Eruptions

Types of volcanic eruptions depend on various factors such as the chemistry of magma,
temperature, viscosity, volume, presence of groundwater, and water and gas content.
Following are the different types of volcanic eruptions:

 Hydrothermal eruption: These eruptions include ash and not magma. They are
driven by the heat caused by hydrothermal systems.
 Phreatic eruption: This is driven when the heat of the magma interacts with the
water. These eruptions do not include magma and only ash.
 Phreatomagmatic eruption: This eruption takes place when there is an interaction
between the newly formed magma and water.
 Strombolian and Hawaiian eruption: Hawaiian eruption has fire fountains while the
Strombolian eruption has explosions due to lava fragments.
 Vulcanian eruption: These eruptions last for a short period of time and can reach up
to a height of 20 km.
 Subplinian and Phinian eruptions: Subplinian eruptions reach up to 20 km in height,
while Plinian eruptions reach up to 20-35 km.
Causes of Volcanic Eruption
1. Due to Density difference in magma
2. Pressure of released gases
3. Injection of new magma

1. Due to Density difference in magma

Due to heat and pressure in the Earth’s mantle, solid rock melt, to form magma. Magma has
the same mass as the solid rock, but more volume, making it lighter. So it will attempt to
rise, if this magma continues to encounter high density material till it reaches the earth’s
crust volcanic eruption occurs.it can either in the form of a lava flow or may be explosive
2. Pressure of released gases
Magma contains dissolved substances such as water, SO2 and CO2. The solubility of magma
decreases with the decrease in pressure as it rises up towards the crust, and the gases get
released in the form of bubbles. When the volume of the gas bubbles in magma reaches
around 75%, magma disintegrates into pyroclasts, a mixture of partially molten and solid
fragments. The bursting of pyroclasts is very explosive and the cause of some of the most
violent eruptions on the surface of the earth.
3. Injection of new magma
When new magma enters a chamber already overflowing with magma, the volcano erupts
due to the additional pressure exerted by the injection of new magma.

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Cyclone
Cyclones are huge revolving storms caused by wind blowing around central area of low
atmospheric pressure.

Causes of cyclones
 Cyclone is caused at low pressure areas.
 Cyclone occurs at the equator. Cyclone is caused by the rising of warm air above the
surface of sea.
 When the warm air rises, the cold air rushes to the empty space.
 Warm temperature at sea surfaces.
 Coriolis force impact area that forms a low-pressure zone.
 Atmospheric instability.
 Increased humidity in the lower to middle levels of the troposphere.
 Low vertical wind shear.
 Pre-existing low-level disturbance or focus.

Cyclone Disaster Management

Mitigation Measures

1. Hazard Mapping – It suggests that using hazard mapping, one can predict the
vulnerable areas affected by the storms. It maps the pattern of old cyclones using
their wind speed, areas affected, flooding frequency etc.
2. Land use planning – With the effective implementation of land use planning, the key
activities and settlements can be avoided in the most vulnerable areas. For example,
a settlement in the floodplains is at utmost risk. Hence, authorities should plan
ahead to avoid such risks.
3. Engineered Structures – These structures withstand the wind forces and prove to
mitigate the losses. The public infrastructure of the country should be designed
keeping in mind the hazard mapping of the cyclone.
4. Retrofitting Non-Engineered Structures – The settlements in non-engineered
structures should ensure that they are aware of their houses’ resistance to the wind
or certain disastrous weather conditions. A few examples of retrofitting the non-
engineered structures given by UN-HABITAT are:
 Construction of a steep-slope roof to avoid the risk of being blown away.
 Anchoring strong posts with solid footings on the ground.
 Plantations of trees at a safe distance from the house to help break the wind
forces.
 Repair of the shelters before time.
5. Cyclone Sheltering – At national, state and regional level, the construction of cyclone
shelters should be taken up to help the vulnerable community from cyclones. The
shelters should be built considering the population density, transportation and

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communication, distance from the affected areas of the past, and the areas’
topography.
6. Flood Management – As the cyclonic storms lead to heavy rainfall that further lead
to flooding in various areas; important should be given to the flood management.
The drainage systems should be well-designed to mitigate flooding. The participation
both from the government and the local community is required for this. (Read
about Floods in the linked article.)
7. Vegetation Cover Improvement – To increase the water infiltration capacity,
improving vegetation cover is of high importance. Planting trees in rows, coastal
shelterbelt plantations, mangrove shelterbelt plantations, etc can help break the
wind force and mitigate the severe losses.
8. Mangrove Plantation – The ecologically-efficient mangroves should be planted
more. India has 3 per cent of the world’s mangroves cover. The root systems of
mangroves help in mitigating tsunamis, soil erosion etc. (Read about important facts,
the significance of Mangroves in the linked article.)
9. Saline Embankment – Along the coast, saline embankments help protect habitation,
agricultural crops, and other important installations.
10. Levees – They act as an obstruction to the wind forces and also provide a shelter
during floods. (Learn about important terms related to rivers in the linked article.)
11. Artificial Hills – These act as the refuge during flooding, and should be taken up in
the right areas.
12. Awareness of the public – The participation of the community increases with the
number of public awareness initiatives. The governments at all levels should initiate
programs bringing awareness about the natural calamities and making provisions for
higher local participation in the mitigation process.

Important Questions
1. Explain briefly the internal structure of the Earth and Mention the
branches Geology related to Civil Engineering.
2. Explain the role of Earth science in the field of Civil Engineering.
3. Explain the following terms with their causes and mitigation measures
a) Tsunami
b) Cyclones
4. Explain the types and causes of Landslide and Volcanic eruption.
5. What are Earthquake? add a short note on types, causes and effects of
Earthquake

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