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Flood
Natural disasters
Hydrological disasters
• Floods
• Limnic eruptions
• Tsunami
Geological disasters
• Avalanches and landslides
• Earthquakes
• Sinkholes
• Volcanic eruptions
Wildfires
Meteorological disasters
• Blizzards
• Cyclonic storms
• Droughts
• Thunderstorms
• Hailstorms
• Heat waves
• Tornado
Space disasters
• Impact events and airburst
• Solar flare
Floods
• A flood is an overflow of water that 'submerges' land
• The EU Floods Directive defines : flood as a temporary
phenomena covering the land with water which is usually not
covered by water
• In the sense of 'flowing water’:
• Flooding may result from the volume of water within a body of
water, which overflows, causing some of the water to escape its
usual boundaries
• While the size of a lake or other body of water will vary with
seasonal changes in precipitation and snow melt, it is not a
significant flood unless the water covers land used by man, like a
village, city or other inhabited area, roads, expanses of farmland,
etc.
• 75% of rainfall is concentrated over four months of monsoon (June -
September) and as a result almost all the rivers carry heavy discharge
during this period. ( South west monsoon)
• Post monsoon season ( North East mansoon) – tamil nadu receives rain
during the months of October and November.
Recent floods in india
• June 2013 North Indian floods: Heavy rain due to cloudburst caused severe floods and
landslides on the North Indian states, mainly Uttarakhand and nearby states. More than
5,700 people were presumed dead
• June 2015 Gujarat flood: Heavy rain in June 2015 resulted in widespread flood in
Saurashtra region of Gujarat resulting in more than 70 deaths. The wild life of Gir Forest
National Park and adjoining area was also affected.
• 2015 South Indian floods: Heavy rain in Nov-Dec 2015 resulted in flooding of Adyar,
Cooum rivers in Chennai, Tamil Nadu resulting in financial loss and human lives.
• 2016 Assam floods: Heavy rains in July–August resulted in floods affecting 1.8 million
people and flooding the Kaziranga National Park killing around 200 wild animals.
• 2017 Gujarat flood: Following heavy rain in July 2017, Gujarat state of India was affected
by the severe flood resulting in more than 200 deaths.
• August 2017 Nepal and India floods
• August 2018 Kerala Flood: Following high rain in late July 2018 and heavy Monsoon
rainfall from August 8, 2018, severe flooding affected the Indian state of Kerala resulting
over 445 deaths
most common causes of flooding
1. Heavy Rains
When it rains heavily, systems gets overwhelmed, and that water doesn’t
drain nearly as quickly as it needs to.
In short, the drainage systems back up, and the water rises
2. Overflowing Rivers
You do not necessarily need to have heavy rains to experience flooding in
your area. For example, if you live along a river and areas upstream from you
experience heavy rains, it could lead to a serious overflow where you live.
Most larger rivers include a series of dams to help manage large amounts of
rainfall, and most river systems are managed by government authorities.
3. Broken Dams
 Aging Dams ( dams running after the design period)
 When heavy rains come, and water levels rise, aging dams can fail and
unleash torrents of water on unsuspecting households.
This is part of what happened after Hurricane Katrina hit New Orleans in 2005.
Levees failed and made the flooding far worse than it would have been otherwise.
4. Urban Drainage Basins
 Many of our cities are made of mostly concrete and other impermeable
material.
 When you have an urban drainage basin that is made of concrete, there
is no ground for water to sink into. So, when those drainage basins fill
up, it is going to mean flooding for low-lying areas.
This is mostly the case in large urban areas —like, Houston and Los Angeles.
When heavy rains strike, the basins used to drain them cannot always handle
the load.
5. Storm Surges and Tsunamis
6. Channels with Steep Sides
Flooding often occurs when there is fast runoff into lakes, rivers and
other reservoirs
7. A Lack of Vegetation
Vegetation can help slow runoff and prevent flooding. When there is a
lack of vegetation, however, there is little to stop water from running
off. This can be a bit of a conundrum after a drought.
While area residents likely welcome the rain, the lack of vegetation after
the drought can cause flash flooding. This does not always happen given
that basins and reservoirs are close to empty, but it can occur in cases of
extreme rains following long periods of drought
8. Melting Snow and Ice
A winter of heavy snow and other precipitation can lead to a spring of
flooding. After all, that snow and ice have to go somewhere when they
melt.
Most mountainous areas experience relatively consistent snowfall totals
from year to year, but an unusually heavy winter of precipitation can spell
bad news for low-lying areas around the mountains when spring hits.
 Flood severity is controlled by the
watershed characteristics
• Basin size (area)
• Topography
• Drainage dentistry (length of streams per area)
• Vegetation type and distributions
• Geology
• Soil type and thickness
• Runoff processes
Floods in India:
The peculiar nature of India’s climate, dominated by monsoons, causes situations
where drought and floods may affect different pockets at the same time of year. The
main reasons for floods in India are:
1. Heavy concentrated rainfall
2. Cyclone and strong winds
3. Inadequate drainage
• Indiscriminate deforestation in catchment areas and upper reaches leads to soil
erosion.
• This in turn causes silting of river courses downstream.
• A thinned soil cover also results in reduction of infiltration and consequent
increase in runoff of large volumes of water.
• Overgrazing, especially in the foothills, leaves the soil without cover and therefore
vulnerable to erosion.
• Unscientific farming practices like shifting cultivation result in loss of vegetation
cover and consequent soil erosion.
Types of flood
1. Coastal Flood
2. Fluvial Flood
3. Pluvial Flood
Coastal (Surge Flood)
A coastal flood, occurs in areas that lie on the coast of a sea,
ocean, or other large body of open water.
 It is typically the result of extreme tidal conditions caused by
severe weather.
Storm surge — produced when high winds from hurricanes and
other storms push water onshore — is the leading cause of coastal
flooding and often the greatest threat associated with a tropical
storm.
 In this type of flood, water overwhelms low-lying land and often
causes devastating loss of life and property.
Coastal flooding is categorized in three levels:
Minor: A slight amount of beach erosion will occur but no major
damage is expected.
Moderate: A fair amount of beach erosion will occur as well as
damage to some homes and businesses.
Major: Serious threat to life and property.
Large-scale beach erosion will occur, numerous roads will be
flooded, and many structures will be damaged. Citizens should review
safety precautions and prepare to evacuate if necessary.
The severity of a coastal flood is determined by several factors,
including the strength,
size,
speed,
and direction of the storm.
• The onshore and offshore topography also plays an important role.
• To determine the probability and magnitude of a storm surge, coastal
flood models consider this information in addition to data from
historical storms that have affected the area, as well as the density of
nearby development.
Fluvial (River Flood)
Riverine flooding, 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 and ice jams.
 The damage from a river flood can be widespread as the overflow
affects smaller rivers downstream, often causing dams and dikes to
break and swamp nearby areas.
There are two main types of riverine flooding:
1. Overbank flooding
occurs when water rises overflows over the edges of a river or
stream.
This is the most common and can occur in any size channel —
from small streams to huge rivers.
2. Flash flooding
 characterized by an intense, high velocity torrent of water that
occurs in an existing river channel with little to no notice.
Flash floods are very dangerous and destructive not only because
of the force of the water, but also the hurtling debris that is often
swept up in the flow.
The severity of a river flood is determined by
the amount of precipitation in an area,
how long it takes for precipitation to accumulate,
previous saturation of local soils,
 and the terrain surrounding the river system.
In flatter areas, floodwater tends to rise more slowly and be
more shallow, and it often remains for days.
In hilly or mountainous areas, floods can occur within minutes
after a heavy rain.
To determine the probability of river flooding, models consider
past precipitation, forecasted precipitation, current river levels,
and temperatures.
Pluvial (Surface Flood)
• A pluvial, or surface water flood, is caused when heavy
rainfall creates a flood event independent of an overflowing
water body.
• One of the most common misconceptions about flood risk is
that one must be located near a body of water to be at risk.
• Pluvial flooding debunks that myth, as it can happen in any
urban area — even higher elevation areas that lie above
coastal and river floodplains.
There are two common types of pluvial flooding:
• Intense rain saturates an urban drainage system. The system
becomes overwhelmed and water flows out into streets and
nearby structures.
• Run-off or flowing water from rain falling on hillsides that are
unable to absorb the water. Hillsides with recent forest fires are
notorious sources of pluvial floods, as are suburban communities
on hillsides.
• Pluvial flooding often occurs in combination with coastal and fluvial
flooding, and although typically only a few centimeters deep, a pluvial
flood can cause significant property damage.
A “100-year flood” is a flood that has a 1% chance of occurring
in any given year
• How to determine the discharge of a “100-year flood?
Impacts
• Moving water has remarkable destructive power.
• When a river overflows its banks or the sea drives inland, structures
poorly equipped to withstand the water’s strength are no match.
• Bridges, houses, trees, and cars can be swept away.
• The erosive force of moving water can drag and carry away the
material constituting the foundation of a building, causing it to
crack and tumble.
The problem of
Sediment deposition
Drainage congestion
Synchronization of river floods compound the flood hazard
with sea tides in the coastal plains
Social Impact
Loss of lives and property:
Immediate impacts of flooding include loss of human life, damage to property,
destruction of crops, loss of livestock, non-functioning of infrastructure
facilities and deterioration of health condition owing to waterborne diseases.
Flash floods, with little or no warning time, cause more deaths than slow-
rising riverine floods.
Loss of livelihoods:
• communication links and infrastructure such as power plants, roads and
bridges are damaged and disrupted, economic activities come to a standstill
• Similarly, the direct effect on production assets, be it in agriculture or industry,
can inhibit regularly activity and lead to loss of livelihoods
• The spill over effects in adjacent non-flooded areas.
• Decreased purchasing and production power:
• Damage to infrastructure causes long-term impacts, such as disruptions to clean water
and electricity, transport, communication, education and health care.
• reduction in purchasing power and loss of land value in the flood plains lead to
increased vulnerabilities of communities living in the area.
• The additional cost of rehabilitation, relocation of people and removal of property
from flood-affected areas can divert the capital required for maintaining production.
• Mass migration:
• Frequent flooding, resulting in loss of livelihoods, production and other prolonged
economic impacts and types of suffering can trigger mass migration or population
displacement.
• Migration to developed urban areas contributes to the overcrowding in the cities.
• Selective out-migration of the workforce sometimes creates complex social problems.
• Psychosocial effects:
• The loss of loved ones can generate deep impacts, especially on children.
• Displacement from one’s home, loss of property and livelihoods and disruption to
business and social affairs can cause continuing stress.
• The stress of overcoming these losses can be overwhelming and produce lasting
psychological impacts.
Hindering economic growth and development:
• The high cost of relief and recovery may adversely impact investment in
infrastructure and other development activities in the area
• Recurrent flooding in a region may discourage long-term investments by the
government and private sector alike.
• Lack of livelihoods, combined with migration of skilled labour and inflation may
have a negative impact on a region’s economic growth.
• Loss of resources can lead to high costs of goods and services, delaying its
development programmes.
Political implications:
• Ineffective response to relief operations during major flood events may lead to
public discontent or loss of trust in the authorities
• Lack of development in flood-prone areas may cause social inequity and even
social unrest posing threat to peace and stability in the region.
Before the floods...
• Know about your local relief centers and evacuation routes.
• Keep emergency numbers and important information handy, as well as emergency supplies, kits,
first aid items. These may include water, canned food, can opener, battery-operated radio,
flashlight and protective clothing.
• Fold and roll up anything onto higher ground (or upper floors of your home), including
chemicals and medicines.
• Make sure everything that is of importance is secured (jewelry, documents, pets, and other
valuables).
• Plant trees and shrubs and keep a lot of vegetation in your compound if you are in a low-lying
area as that can control erosion and help soften the
speed of the
flowing water.
 During the floods...
• Flash floods occur in a short spate of time. As soon as they start, be quick,
keep safe and ensure that children and elderly are safe by leaving the house
to a higher ground.
• Turn off all electrical appliance, gas, heating and the like if there is a bit of
time.
• Leave the area before it gets too late. Do not drive through the water as
moving water can sweep you away.
• Stay away from power lines or broken power transmission cables.
• Try to keep away from flood water as it may contain chemicals or other
hazardous materials.
 After flood
• Make sure you have permission from emergency officers to get back
inside your house.
• Keep all power and electrical appliance off until the house is cleaned
up properly and an electrical personnel has confirmed that it is OK to
put them on.
• Make sure you have photographs, or a record of all the damage, as it
may be needed for insurance claims.
• Clean the entire home, together with all the objects in it very well
before you use them again. They may be contaminated.
• Wear appropriate gear (mask and gloves) before cleaning begins.

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flood

  • 2. Natural disasters Hydrological disasters • Floods • Limnic eruptions • Tsunami Geological disasters • Avalanches and landslides • Earthquakes • Sinkholes • Volcanic eruptions Wildfires Meteorological disasters • Blizzards • Cyclonic storms • Droughts • Thunderstorms • Hailstorms • Heat waves • Tornado Space disasters • Impact events and airburst • Solar flare
  • 3. Floods • A flood is an overflow of water that 'submerges' land • The EU Floods Directive defines : flood as a temporary phenomena covering the land with water which is usually not covered by water • In the sense of 'flowing water’: • Flooding may result from the volume of water within a body of water, which overflows, causing some of the water to escape its usual boundaries • While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, it is not a significant flood unless the water covers land used by man, like a village, city or other inhabited area, roads, expanses of farmland, etc.
  • 4. • 75% of rainfall is concentrated over four months of monsoon (June - September) and as a result almost all the rivers carry heavy discharge during this period. ( South west monsoon) • Post monsoon season ( North East mansoon) – tamil nadu receives rain during the months of October and November.
  • 5. Recent floods in india • June 2013 North Indian floods: Heavy rain due to cloudburst caused severe floods and landslides on the North Indian states, mainly Uttarakhand and nearby states. More than 5,700 people were presumed dead • June 2015 Gujarat flood: Heavy rain in June 2015 resulted in widespread flood in Saurashtra region of Gujarat resulting in more than 70 deaths. The wild life of Gir Forest National Park and adjoining area was also affected. • 2015 South Indian floods: Heavy rain in Nov-Dec 2015 resulted in flooding of Adyar, Cooum rivers in Chennai, Tamil Nadu resulting in financial loss and human lives. • 2016 Assam floods: Heavy rains in July–August resulted in floods affecting 1.8 million people and flooding the Kaziranga National Park killing around 200 wild animals. • 2017 Gujarat flood: Following heavy rain in July 2017, Gujarat state of India was affected by the severe flood resulting in more than 200 deaths. • August 2017 Nepal and India floods • August 2018 Kerala Flood: Following high rain in late July 2018 and heavy Monsoon rainfall from August 8, 2018, severe flooding affected the Indian state of Kerala resulting over 445 deaths
  • 6. most common causes of flooding 1. Heavy Rains When it rains heavily, systems gets overwhelmed, and that water doesn’t drain nearly as quickly as it needs to. In short, the drainage systems back up, and the water rises 2. Overflowing Rivers You do not necessarily need to have heavy rains to experience flooding in your area. For example, if you live along a river and areas upstream from you experience heavy rains, it could lead to a serious overflow where you live. Most larger rivers include a series of dams to help manage large amounts of rainfall, and most river systems are managed by government authorities.
  • 7. 3. Broken Dams  Aging Dams ( dams running after the design period)  When heavy rains come, and water levels rise, aging dams can fail and unleash torrents of water on unsuspecting households. This is part of what happened after Hurricane Katrina hit New Orleans in 2005. Levees failed and made the flooding far worse than it would have been otherwise. 4. Urban Drainage Basins  Many of our cities are made of mostly concrete and other impermeable material.  When you have an urban drainage basin that is made of concrete, there is no ground for water to sink into. So, when those drainage basins fill up, it is going to mean flooding for low-lying areas. This is mostly the case in large urban areas —like, Houston and Los Angeles. When heavy rains strike, the basins used to drain them cannot always handle the load.
  • 8. 5. Storm Surges and Tsunamis 6. Channels with Steep Sides Flooding often occurs when there is fast runoff into lakes, rivers and other reservoirs 7. A Lack of Vegetation Vegetation can help slow runoff and prevent flooding. When there is a lack of vegetation, however, there is little to stop water from running off. This can be a bit of a conundrum after a drought. While area residents likely welcome the rain, the lack of vegetation after the drought can cause flash flooding. This does not always happen given that basins and reservoirs are close to empty, but it can occur in cases of extreme rains following long periods of drought
  • 9. 8. Melting Snow and Ice A winter of heavy snow and other precipitation can lead to a spring of flooding. After all, that snow and ice have to go somewhere when they melt. Most mountainous areas experience relatively consistent snowfall totals from year to year, but an unusually heavy winter of precipitation can spell bad news for low-lying areas around the mountains when spring hits.
  • 10.  Flood severity is controlled by the watershed characteristics • Basin size (area) • Topography • Drainage dentistry (length of streams per area) • Vegetation type and distributions • Geology • Soil type and thickness • Runoff processes
  • 11. Floods in India: The peculiar nature of India’s climate, dominated by monsoons, causes situations where drought and floods may affect different pockets at the same time of year. The main reasons for floods in India are: 1. Heavy concentrated rainfall 2. Cyclone and strong winds 3. Inadequate drainage • Indiscriminate deforestation in catchment areas and upper reaches leads to soil erosion. • This in turn causes silting of river courses downstream. • A thinned soil cover also results in reduction of infiltration and consequent increase in runoff of large volumes of water. • Overgrazing, especially in the foothills, leaves the soil without cover and therefore vulnerable to erosion. • Unscientific farming practices like shifting cultivation result in loss of vegetation cover and consequent soil erosion.
  • 12. Types of flood 1. Coastal Flood 2. Fluvial Flood 3. Pluvial Flood
  • 13. Coastal (Surge Flood) A coastal flood, occurs in areas that lie on the coast of a sea, ocean, or other large body of open water.  It is typically the result of extreme tidal conditions caused by severe weather. Storm surge — produced when high winds from hurricanes and other storms push water onshore — is the leading cause of coastal flooding and often the greatest threat associated with a tropical storm.  In this type of flood, water overwhelms low-lying land and often causes devastating loss of life and property.
  • 14. Coastal flooding is categorized in three levels: Minor: A slight amount of beach erosion will occur but no major damage is expected. Moderate: A fair amount of beach erosion will occur as well as damage to some homes and businesses. Major: Serious threat to life and property. Large-scale beach erosion will occur, numerous roads will be flooded, and many structures will be damaged. Citizens should review safety precautions and prepare to evacuate if necessary.
  • 15. The severity of a coastal flood is determined by several factors, including the strength, size, speed, and direction of the storm. • The onshore and offshore topography also plays an important role. • To determine the probability and magnitude of a storm surge, coastal flood models consider this information in addition to data from historical storms that have affected the area, as well as the density of nearby development.
  • 16.
  • 17. Fluvial (River Flood) Riverine flooding, 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 and ice jams.  The damage from a river flood can be widespread as the overflow affects smaller rivers downstream, often causing dams and dikes to break and swamp nearby areas.
  • 18. There are two main types of riverine flooding: 1. Overbank flooding occurs when water rises overflows over the edges of a river or stream. This is the most common and can occur in any size channel — from small streams to huge rivers. 2. Flash flooding  characterized by an intense, high velocity torrent of water that occurs in an existing river channel with little to no notice. Flash floods are very dangerous and destructive not only because of the force of the water, but also the hurtling debris that is often swept up in the flow.
  • 19. The severity of a river flood is determined by the amount of precipitation in an area, how long it takes for precipitation to accumulate, previous saturation of local soils,  and the terrain surrounding the river system. In flatter areas, floodwater tends to rise more slowly and be more shallow, and it often remains for days. In hilly or mountainous areas, floods can occur within minutes after a heavy rain. To determine the probability of river flooding, models consider past precipitation, forecasted precipitation, current river levels, and temperatures.
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  • 21. Pluvial (Surface Flood) • A pluvial, or surface water flood, is caused when heavy rainfall creates a flood event independent of an overflowing water body. • One of the most common misconceptions about flood risk is that one must be located near a body of water to be at risk. • Pluvial flooding debunks that myth, as it can happen in any urban area — even higher elevation areas that lie above coastal and river floodplains.
  • 22. There are two common types of pluvial flooding: • Intense rain saturates an urban drainage system. The system becomes overwhelmed and water flows out into streets and nearby structures. • Run-off or flowing water from rain falling on hillsides that are unable to absorb the water. Hillsides with recent forest fires are notorious sources of pluvial floods, as are suburban communities on hillsides. • Pluvial flooding often occurs in combination with coastal and fluvial flooding, and although typically only a few centimeters deep, a pluvial flood can cause significant property damage.
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  • 24. A “100-year flood” is a flood that has a 1% chance of occurring in any given year • How to determine the discharge of a “100-year flood?
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  • 29. Impacts • Moving water has remarkable destructive power. • When a river overflows its banks or the sea drives inland, structures poorly equipped to withstand the water’s strength are no match. • Bridges, houses, trees, and cars can be swept away. • The erosive force of moving water can drag and carry away the material constituting the foundation of a building, causing it to crack and tumble. The problem of Sediment deposition Drainage congestion Synchronization of river floods compound the flood hazard with sea tides in the coastal plains
  • 30. Social Impact Loss of lives and property: Immediate impacts of flooding include loss of human life, damage to property, destruction of crops, loss of livestock, non-functioning of infrastructure facilities and deterioration of health condition owing to waterborne diseases. Flash floods, with little or no warning time, cause more deaths than slow- rising riverine floods. Loss of livelihoods: • communication links and infrastructure such as power plants, roads and bridges are damaged and disrupted, economic activities come to a standstill • Similarly, the direct effect on production assets, be it in agriculture or industry, can inhibit regularly activity and lead to loss of livelihoods • The spill over effects in adjacent non-flooded areas.
  • 31. • Decreased purchasing and production power: • Damage to infrastructure causes long-term impacts, such as disruptions to clean water and electricity, transport, communication, education and health care. • reduction in purchasing power and loss of land value in the flood plains lead to increased vulnerabilities of communities living in the area. • The additional cost of rehabilitation, relocation of people and removal of property from flood-affected areas can divert the capital required for maintaining production. • Mass migration: • Frequent flooding, resulting in loss of livelihoods, production and other prolonged economic impacts and types of suffering can trigger mass migration or population displacement. • Migration to developed urban areas contributes to the overcrowding in the cities. • Selective out-migration of the workforce sometimes creates complex social problems. • Psychosocial effects: • The loss of loved ones can generate deep impacts, especially on children. • Displacement from one’s home, loss of property and livelihoods and disruption to business and social affairs can cause continuing stress. • The stress of overcoming these losses can be overwhelming and produce lasting psychological impacts.
  • 32. Hindering economic growth and development: • The high cost of relief and recovery may adversely impact investment in infrastructure and other development activities in the area • Recurrent flooding in a region may discourage long-term investments by the government and private sector alike. • Lack of livelihoods, combined with migration of skilled labour and inflation may have a negative impact on a region’s economic growth. • Loss of resources can lead to high costs of goods and services, delaying its development programmes. Political implications: • Ineffective response to relief operations during major flood events may lead to public discontent or loss of trust in the authorities • Lack of development in flood-prone areas may cause social inequity and even social unrest posing threat to peace and stability in the region.
  • 33. Before the floods... • Know about your local relief centers and evacuation routes. • Keep emergency numbers and important information handy, as well as emergency supplies, kits, first aid items. These may include water, canned food, can opener, battery-operated radio, flashlight and protective clothing. • Fold and roll up anything onto higher ground (or upper floors of your home), including chemicals and medicines. • Make sure everything that is of importance is secured (jewelry, documents, pets, and other valuables). • Plant trees and shrubs and keep a lot of vegetation in your compound if you are in a low-lying area as that can control erosion and help soften the speed of the flowing water.
  • 34.  During the floods... • Flash floods occur in a short spate of time. As soon as they start, be quick, keep safe and ensure that children and elderly are safe by leaving the house to a higher ground. • Turn off all electrical appliance, gas, heating and the like if there is a bit of time. • Leave the area before it gets too late. Do not drive through the water as moving water can sweep you away. • Stay away from power lines or broken power transmission cables. • Try to keep away from flood water as it may contain chemicals or other hazardous materials.
  • 35.  After flood • Make sure you have permission from emergency officers to get back inside your house. • Keep all power and electrical appliance off until the house is cleaned up properly and an electrical personnel has confirmed that it is OK to put them on. • Make sure you have photographs, or a record of all the damage, as it may be needed for insurance claims. • Clean the entire home, together with all the objects in it very well before you use them again. They may be contaminated. • Wear appropriate gear (mask and gloves) before cleaning begins.

Editor's Notes

  1. Such natural and man-made disasters to which India severely exposes itself or herself every year, which often lead to the depletion of natural resources. Natural disasters are natural phenomenon and occur without any intention while man-made disasters are events which, either intentionally or by accident cause severe threats to public health and well-being.  Because their occurrence is unpredictable, man-made disasters pose an especially challenging threat that must be dealt with through vigilance, and proper preparedness and response. Floods A flood is an overflow of water that 'submerges' land. The EU Floods Directive defines a flood as a temporary covering the land with water which is usually not covered by water.In the sense of 'flowing water', the word may also be applied to the inflow of the tides. Flooding may result from the volume of water within a body of water, such as a river or lake, which overflows, causing some of the water to escape its usual boundaries. While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, it is not a significant flood unless the water covers land used by man, like a village, city or other inhabited area, roads, expanses of farmland, etc. Limnic eruptions A limnic eruption occurs when a gas, usually CO2, suddenly erupts from deep lake water, posing the threat of suffocating wildlife, livestock and humans. Such an eruption may also cause tsunamis in the lake as the rising gas displaces water. Scientists believe landslides, volcanic activity, or explosions can trigger such an eruption. To date, only two limnic eruptions have been observed and recorded. In 1984, in Cameroon, a limnic eruption in Lake Monoun caused the deaths of 37 nearby residents, and at nearby Lake Nyos in 1986 a much larger eruption killed between 1,700 and 1,800 people by asphyxiation. Tsunami A tsunami (plural: tsunamis or tsunami; from Japanese: 津波, lit. "harbour wave"; English pronunciation: /tsuːˈnɑːmi/), also known as a seismic sea wave or as a tidal wave, is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Tsunamis can be caused by undersea earthquakes such as the 2004 Boxing Day tsunami, or by landslides such as the one in 1958 at Lituya Bay, Alaska, or by volcanic eruptions such as the ancient eruption of Santorini. On March 11, 2011, a tsunami occurred near Fukushima, Japan and spread through the Pacific. Avalanches and landslides A landslide is described as an outward and downward slope movement of an abundance of slope-forming materials including rock, soil, artificial, or even a combination of these things. During World War I, an estimated 40,000 to 80,000 soldiers died as a result of avalanches during the mountain campaign in the Alps at the Austrian-Italian front. Many of the avalanches were caused by artillery fire.[6][7] Earthquakes An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. At the Earth's surface, earthquakes manifest themselves by vibration, shaking, and sometimes displacement of the ground. Earthquakes are caused by slippage within geological faults. The underground point of origin of the earthquake is called the seismic focus. The point directly above the focus on the surface is called the epicenter. Earthquakes by themselves rarely kill people or wildlife. It is usually the secondary events that they trigger such as building collapse, fires, tsunamis (seismic sea waves) and volcanoes. Many of these could possibly be avoided by better construction, safety systems, early warning and planning. Sinkholes When natural erosion or human mining makes the ground too weak to support the structures built on it, the ground can collapse and produce a sinkhole. For example, the 2010 Guatemala City sinkhole which killed fifteen people was caused when heavy rain from Tropical Storm Agatha, diverted by leaking pipes into a pumice bedrock, led to the sudden collapse of the ground beneath a factory building. Volcanic eruptions Volcanoes can cause widespread destruction and consequent disaster in several ways. The effects include the volcanic eruption itself that may cause harm following the explosion of the volcano or falling rocks. Secondly, lava may be produced during the eruption of a volcano, and so as it leaves the volcano the lava destroys many buildings, plants and animals due to its extreme heat. Thirdly, volcanic ash, generally meaning the cooled ash, may form a cloud, and settle thickly in nearby locations. When mixed with water this forms a concrete-like material. In sufficient quantities, ash may cause roofs to collapse under its weight but even small quantities will harm humans if inhaled. Since the ash has the consistency of ground glass it causes abrasion damage to moving parts such as engines. The main killer of humans in the immediate surroundings of a volcanic eruption is the pyroclastic flows, which consist of a cloud of hot volcanic ash which builds up in the air above the volcano and rushes down the slopes when the eruption no longer supports the lifting of the gases. It is believed that Pompeii was destroyed by a pyroclastic flow.
  2. Here are eight of the most common causes of flooding, both natural and human-induced: 1. Heavy Rains The simplest explanation for flooding is heavy rains. No matter where you live, you are surrounded by infrastructure and systems designed to move rainwater into appropriate basins and reservoirs. In most cases, the infrastructure does its job, and you never have to think about where the rain goes when it runs off. When it rains heavily, however, those systems are overwhelmed, and that water doesn’t drain nearly as quickly as it needs to. In short, the drainage systems back up, and the water rises — sometimes into homes. This typically happens only in cases of sustained heavy rains over a long period. 2. Overflowing Rivers You do not necessarily need to have heavy rains to experience flooding in your area. For example, if you live along a river and areas upstream from you experience heavy rains, it could lead to a serious overflow where you live. Most larger rivers include a series of dams to help manage large amounts of rainfall, and most river systems are managed by government authorities. Sometimes, however, those authorities have to make tough decisions about how to operate dams. They often can manage the water and prevent flooding altogether — but not always. 3. Broken Dams Much of America’s infrastructure was built in the 20th century, so it is getting old. When heavy rains come, and water levels rise, aging dams can fail and unleash torrents of water on unsuspecting households. This is part of what happened after Hurricane Katrina hit New Orleans in 2005. Levees failed and made the flooding far worse than it would have been otherwise. While we have come to depend on 20th-century architecture, and much of it does its job well, there is always a possibility that a structure will fail. 4. Urban Drainage Basins Many of our cities are made of mostly concrete and other impermeable material. When you have an urban drainage basin that is made of concrete, there is no ground for water to sink into. So, when those drainage basins fill up, it is going to mean flooding for low-lying areas. This is mostly the case in large urban areas — think Houston and Los Angeles. When heavy rains strike, the basins used to drain them cannot always handle the load. 5. Storm Surges and Tsunamis Rain is not always the culprit when it comes to flooding. Storm surges related to hurricanes and other storms can lead to significant flooding, as can tsunamis that are sometimes caused by underwater earthquakes. Given modern technology, we often know about storm surges and tsunamis before they arrive, but this is not always the case. For example, in 2004, an earthquake off the coast of Indonesia created a tsunami that gave little warning before coming ashore. 6. Channels with Steep Sides Flooding often occurs when there is fast runoff into lakes, rivers and other reservoirs. This is often the case with rivers and other channels that feature steep sides. It is a similar issue to having a lack of vegetation, which is explained in more detail below. 7. A Lack of Vegetation Vegetation can help slow runoff and prevent flooding. When there is a lack of vegetation, however, there is little to stop water from running off. This can be a bit of a conundrum after a drought. While area residents likely welcome the rain, the lack of vegetation after the drought can cause flash flooding. This does not always happen given that basins and reservoirs are close to empty, but it can occur in cases of extreme rains following long periods of drought. 8. Melting Snow and Ice A winter of heavy snow and other precipitation can lead to a spring of flooding. After all, that snow and ice have to go somewhere when they melt. Most mountainous areas experience relatively consistent snowfall totals from year to year, but an unusually heavy winter of precipitation can spell bad news for low-lying areas around the mountains when spring hits.
  3. Leeves are the embankment built to prevent the overflow of river
  4. Among the severely affected areas of the country are the Brahmaputra valleys, north Bihar (Kosi River and north Gangetic plain) and lower West Bengal. Apart from these, floods affect large areas in the following belts: The lower courses of rivers in the north Indian plains which get silted and change their courses. Such situations are prevalent in the states of Punjab, Haryana, Himachal Pradesh, Delhi, Rajasthan, Uttar Pradesh, Bihar and West Bengal Inadequate drainage in parts of Haryana and Punjab is the main cause of inundation. The tributaries of the Indus – the Jhelum, Satluj, Beas, Ravi and Chenab – cause floods in Jammu and Kashmir, Punjab, Haryana, western Uttar Pradesh and Himachal Pradesh. Certain areas in central India and the peninsula get flooded by the Narmada, Tapti, Chambal, Godavari, Krishna, Cauveri and Pennar. Large tracts along the east coast get flooded due to cyclonic storms. The total area affected by floods in India is between 7.5 million hectares and 10 million heactares. Eastern Uttar Pradesh and northern Bihar are the worst affected regions of the country.
  5. When floodwaters recede, affected areas are often blanketed in silt and mud. The water and landscape can be contaminated with hazardous materials, such as sharp debris, pesticides, fuel, and untreated sewage. Potentially dangerous mold blooms can quickly grow over water-soaked materials. Residents of flooded areas can be left without power and clean drinking water. Contamination of soil and groundwater leads to outbreaks of deadly waterborne diseases like typhoid, hepatitis A, and cholera. Flooding, particularly in river floodplains, brings with it some good things too. The famous fertile floodplains of the Mississippi Valley in the American Midwest, the Nile River valley in Egypt, and the Tigris-Euphrates in the Middle East have supported agriculture for millennia because annual flooding brings with it millions of tons of nutrient-rich silt.