A descriptive presentation on natural hazards i.e. Floods and Avalanches. Their causes and impact and effects on human life and environment

1. GEOLOGICAL HAZARDS
Submitted to- Submitted by-
Dr. Alka Kataria Ms. Deeksha Sharma
Msc Sem I
ICG/2017/23863

2. Floods
o Introduction
• Characteristics of
flood
• Types of floods
o Causes
o Effects
• On human life
• On environment
o Flood prone areas
o Flood management

3. Floods

4.  Flood is overflow of excess water that
submerges land and inflow of tide onto land.
 Flood is usually caused by rain, heavy
thunderstorms, and thawing of snow.
 Its considered to be a temporary condition of
two or more acres of dry land either:
• Overflowed with inland or tidal waters
• Rapid or runoff of surface waters
• Mudflows

5.  Number of criteria determine the dangers of a
flood.
• Velocity- high velocities of flow create erosive forces
and can do things like destroy foundations.
• Depth of Water- floatation, failures on foundation,
vegetation survival, etc..
• Rate of Rise- is the rate at which the water level
increases.
• Seasonal- the land during growing season, the effects
on agriculture production and other things like that.

6.  Three common types of floods are-
TYPES OF FLOODS
COASTAL
(SURGE FLOOD)
RIVERINE
(RIVER FLOOD)
PLUVIAL
( SURFACE FLOOD)

7. COASTAL (SURGE FLOOD)
 Occurs in areas that lie on the coast of a sea, ocean,
or other large body of open water.
 typically the result of extreme tidal conditions
caused by severe weather.
 In this type of flood, water overwhelms low-lying
land and often causes devastating loss of life and
property.
 Coastal floods are categorized in three levels-
• Minor –slight amount of beach erosion, no major damage
is expected
• Moderate- fair amount of beach erosion, damage to some
homes and businesses.
• Major- Large-scale beach erosion, Serious threat to life
and property.

8. India coastal flood
India coastal flood

9. RIVERINE ( RIVER FLOOD)
 Occurs when excessive rainfall over an
extended period of time causes a river to
exceed its capacity.
 It can also be caused by heavy snow melt
 There are two main types of riverine flooding-
• Overbank flooding- occurs when water rises
overflows over the edges of a river or stream.
• Flash flooding- characterized by an intense, high
velocity torrent of water that occurs in an existing
river channel with little to no notice.

10. Submerged bridge in Rudraprayag

11. PLUVIAL (SURFACE FLOOD)
 caused when heavy rainfall creates a
flood event independent of an
overflowing water body.
 Pluvial flooding debunks that myth, that
one must be located near a body of water
to be at risk.
 There are two common types of pluvial
flooding:
• Intense rain saturates an urban drainage system.
• Run-off or flowing water from rain falling on
hillsides that are unable to absorb the water.

12. Roads after heavy rainfall

13. Natural-
• Heavy rains
• Melting of ice during volcano eruption
• Undersea earthquake
• Marine landslip
Man made-
• Bank erosion
• Breach of dam/ barrage/embankment

14. PRIMARY SECONDARY TERTIARY
Due to direct
contact of flood
water
Due to result of
primary effects
Due to combined
effect of 1º and
2ºeffects
Physical damage
• loss of lives
• Damage to
buildings, bridge,
crops, livestock
Disruption of
essential services
• Electricity
• Gas
• Health hazards
Long term effects
•Change in location
of river channels
•Destruction of farm
lands and wildlife
habitat

15. PRIMARY EFFECTS SECONDARY EFFECTS TERTIARY EFFECTS

16. • Soil becomes poor because the
oxygen is limited due to so much
water.
• The pH in soil decreases.
• rate decomposition of organic
matter in flooded soil tends only to
be half that unflooded soil.
• Trees are effected as well. It effects
the height, age, vigor, roots, and
species
• During the growing season
flooding is very harmful especially
to plants.

18. Cannot be absolutely controlled only managed
Aims of flood management-
•Protection of people & property
•Reduction of flood risk
•Monitoring, research, forecasting & warning

19. STRUCTURAL NON-STRUCTURAL
• Embankments • Flood preparedness
• Dams & reservoirs • Flood forecasting
• Drainage improvement • Afforestation
• Diversion of flood rivers • Public relief

20.  Embankment
 Dams and reservoirs

21.  Drainage improvement
 Diversion of flood rivers

22.  Flood prepardness
 Flood forecasting

23.  Afforestation

24. THANKYOU