ppt on floods
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A flood is an overflow of an expanse of water thatsubmerges land
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FLOODS LEAD TO .
Overflow situation
damage in terms of
life, property and
economic loss.
Thousands of
crores of rupees
are spent everyyear in flood control
and forecasting.
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Reasons for flood
Heavy rainfall(
26.7.2005)
Huge snow melting
Failures of dams,
barrages etc.,(koshi)
Landslides causing
blockage of river Tsunami
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Types of flood(cont..)
Coastal floods
Caused by severe sea storms, or as a result of
another hazard (e.g. tsunami or hurricane).
Catastrophic floods
Caused by a significant and unexpected event
e.g. dam breakage, or as a result of another
hazard (e.g. earthquake or volcanic eruption).
Muddy floods
A muddy flood is generated by run off on crop
land.
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Why flood matters??
EFFECTS The damage due to flood may vary with respect to the
magnitude of the flood.
Thus we can classify the effects as:
Primary effects
Physical damage- Can range anywhere from bridges,cars,buildings, sewer systems, roadways, canals and any othertype of structure.
Casualties- People and livestock die due to drowning. It canalso lead to epidemics and diseases.
Secondary effects
Water supplies- Contamination of water. Clean drinking waterbecomes scarce.
Diseases- Unhygienic conditions. Spread of water-bornediseases
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Effects (cont..)
Crops and food supplies- Shortage of foodcrops can be caused due to loss of entire
harvest.
Trees- Non-tolerant species can die fromsuffocation
Tertiary/long-term effects
Economic-, rebuilding costs, food shortageleading to price increase, temporary decline in
tourism etc.
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F
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IN
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Floods In Mumbai
The Maharashtra floods of 2005 refers to the flooding of
many parts of the Indian state of Maharashtra including
large areas of the metropolis Mumbai, a city located on
the coast of the Arabian Sea, on the western coast of
India, in which at least 5,000 people died.
The term 26 July, now is, in context always used for theday when the city of Mumbai came to a standstill.
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Overview The floods were caused by the eighth heaviest ever recorded 24-hour
rainfall figure of 994 mm (39.1 inches) which lashed the metropolis on 26
July 2005, and intermittently continued for the next day. 644 mm
(25.4 inches) was received within the 12-hr period between 8am and 8pm.
The previous record high rainfall in a 24-hour period for Mumbai was 575
mm (22.6 inches) in 1974.
People were returning home from work. Many people halted in theiroffices.
Thousands of people were affected badly. Infact every family or person
must be having a story for 26th July.
Even animals died. Animals were drowned in sheds and streets affected
by floods. Plants and agriculture was destroyed to an greater extent.
Thousands of animal carcasses floated in the flood waters, raising
concerns about the possibility of disease.
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Causes of Floods in Mumbai
The expansion of Mumbai city inthe past couple of decades hasbeen beyond limits
Unplanned infrastructure atBandra-Kurla, Kalina etc, wasthe main reason for the chest
high water clogging in thoseplaces
Officials in the environmentministry claimed that it was notpractical to impose newguidelines with retrospectiveeffect "as there are millions of
buildings". Improper maintenance of
drainage systems all overMumbai
Both government and people areresponsible
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FLOOD CONTROL
Greater losses due to flood
Need for control, Measures to be taken
No complete control of flood to zero level
So Flood Management rather than Flood
Control
Classification of control measures
Structural measures and 2. Non-structuralmeasures
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Flood Control
Storage Reservoir
Detentio Reservoir Levees
Floodways
ChannelImprovement
WatershedManagement
Flood Plain zoning
Flood forecastingand Warning
Evacuation and
relocation
Structural Measure Non-Structural Measure
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Stuctural Measures
STORAGE RESERVOIR:
Most reliable and effective flood control
method
Storage reservoir to absorb incoming flood
Release in controlled way so that downstream
channels do not get flooded.
Several reservoirs to be placed in a river forcomplete flood control.
Graph Kheichera rakhnu hai
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Structural Measures (cont..)
DETENTION RESERVIORS
-Consist of an obstruction to a river with
uncontrolled outlet.
-For small structures and temporary storage
LEVEES
-Also called dikes or flood embankments
-Earthen structures parallel to the course ofriver.
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Structural Measures
Height higher than
the design flood
level.
One of the oldestand common
methods of flood
protection
Considerable care
and maintenance
required since
earthen
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Structural Measures
FLOODWAYS
-Channels into which part of the flood will be
diverted during high stages.
-Natural or man-made
CHANNEL IMPROVEMENT
-Widening or deepening of channel
-Reduction of channel roughness (clearance ofvegetation)
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Structural Measures
WATERSHED MANAGEMENT
-Aims at cutting down and delaying the runoff
before it gets into the river.
-Check dams, contour bonding, terraces etc.
-Improve soil infiltration capacity hence reduce
soil erosion
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NON-STRUCTURAL METHODS
FLOOD PLAIN ZONING
Identifies the flood prone areas of a river andregulates the land use to restrict the damage dueto flood.
Development plans are prepared
FLOOD FORECASTING AND WARNING
Enables civil authority to take appropriate controlmeasures.
Orbiting satellitesPicturesCloud growthrainfall predictionflood prediction
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Non-structural methods
-historical recordsof flooding withstudy on theparameters: season,river channeltopography, soilconditions, rainfallintensity andweather.
Study of FLOODHYDROGRAPH
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Flood hydrograph
Hydrograph: Study of the hydrological characteristics of acatchment.
Responses of a given catchment to a rainfall input.
USES
Use in the design of hydraulic structures
Development of flood forecasting and warming systems based onrainfall
Extension of flood flow records based on rainfall records
(components of hydrograph: \
1.Rising limb 2. Crest segment 3. Recession limb)
Factors affecting flood hydrograph: Physiographic and climatic factors
Limitations
Precipitation must be from rainfall only
Non uniform pptdoesnt give good results (unit hydrograph)
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Flood hydrograph
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Non-structural measure
EVACUATION AND RELOCATION
Evacuation of communities along with their live
stocks and other valuables.
TemporarilyNonstructural measure,Permanent resettlementStructural measure
Decrease loss burden
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Conclusion
-Flood is one ofdeadliest naturaldisaster.
-Preventive measuresto be taken in time.
-Better engineeringstructures to preventflood control
-Stringent governmentsteps.
-Awareness on flooddisaster is required.
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Deadliest floodsDeath Toll Event Location Date
1)2,500,000-3,700,000 China floods China 1931
2)900,000
2,000,000 Yellow River (Huang He) floodChina 1887
3)500,000700,000 1938 Yellow River (Huang He) flood
China 1938
4)231,000 Banqiao Dam failure, result ofTyphoon Nina.Approximately 86,000 people died from flooding
and another 145,000 died during subsequent disease.China 1975
5)145,000 Yangtze river floodChina 1935
6)More than
100,000St. Felix's Flood, storm surge Netherlands 1530
7)100,000 Hanoi and Red River Delta flood North Vietnam 1971
8)100,000 Yangtze river flood China 1911
Th k f ki d
http://f/Documents%20and%20Settings/Administrator/Desktop/flood/Flood%20-%20Wikipedia,%20the%20free%20encyclopedia.mht -
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Thankyou for your kind
attention!!
Any question?????